explain me anti microbial drugs as per gobind rai pharma cology and bhalani ..do not any single thing explain me as you are a pharmacology teacher teaching student in simplest and easy way possible but also with depth

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The specific Gobind Rai Garg and Bhalani textbooks are not in the library, but we have Katzung and Lippincott Pharmacology. Let me pull comprehensive antimicrobial content from both - these cover the same syllabus content as Indian pharmacology textbooks.

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Let me search directly in the pharmacology books for antimicrobial drug chapters:

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Excellent! Now let me read the key sections from Lippincott and Katzung:

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I now have rich content from both textbooks. Let me also get the Lippincott section on mechanism classification and the Katzung section on non-beta-lactam drugs:

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I now have comprehensive content from both pharmacology textbooks. Let me now write the complete, teacher-style explanation. This will be a thorough, well-organized response covering everything a pharmacology student needs to know about antimicrobial drugs.

🦠 ANTIMICROBIAL DRUGS - Complete Pharmacology Lecture

Sources: Katzung's Basic & Clinical Pharmacology 16th Ed + Lippincott Illustrated Reviews Pharmacology

PART 1: THE CONCEPT - What Are Antimicrobial Drugs?

Think of your body as a house and bacteria/fungi/viruses as unwanted intruders. Antimicrobial drugs are your security guards - but here is the important twist:

Selective Toxicity is the golden principle. These drugs must kill or harm the invader WITHOUT harming YOUR own cells. They exploit the biochemical differences between microorganisms and human cells. For example, bacteria have a cell wall made of peptidoglycan - human cells have NO such wall. So if you design a drug that attacks the cell wall, it kills the bacteria but leaves your cells untouched.

However, selective toxicity is usually relative, not absolute - meaning the concentration must be carefully controlled so it targets the bug but remains tolerable by the host.

"Antimicrobial drugs take advantage of biochemical differences that exist between microorganisms and human beings." - Lippincott Pharmacology

PART 2: CLASSIFICATION OF ANTIMICROBIAL DRUGS

There are three ways to classify them:

A. By Mechanism of Action (Most Important!)

Mechanism	Example Drugs
Inhibit cell wall synthesis	Penicillins, Cephalosporins, Carbapenems, Vancomycin
Disrupt cell membrane	Polymyxins, Amphotericin B
Inhibit protein synthesis (30S ribosome)	Aminoglycosides, Tetracyclines
Inhibit protein synthesis (50S ribosome)	Macrolides, Chloramphenicol, Clindamycin
Inhibit nucleic acid synthesis	Fluoroquinolones (DNA gyrase), Rifampicin (RNA polymerase), Metronidazole
Inhibit metabolic pathways (folate)	Sulfonamides, Trimethoprim

Think of this as attacking different parts of the bacteria's factory: cell wall construction, outer skin, protein-making machines, DNA copying machines, and vitamin factory.

B. By Spectrum of Activity

Narrow Spectrum - kills only a limited type (e.g., Penicillin G kills mainly gram-positive organisms)
Extended Spectrum - covers gram-positive + some gram-negative (e.g., Ampicillin)
Broad Spectrum - effective against a wide variety of bacteria (e.g., Carbapenems, Tetracyclines)

C. By Type of Killing

Type	How it works	Examples
Bactericidal	Kills bacteria directly	Penicillins, Aminoglycosides, Fluoroquinolones
Bacteriostatic	Stops bacteria from multiplying (immune system finishes the job)	Tetracyclines, Chloramphenicol, Macrolides, Sulfonamides

Remember: Bactericidal = Killer. Bacteriostatic = Stopper. In immunocompromised patients, you always prefer bactericidal drugs because their immune system cannot do the finishing work.

PART 3: HOW TO SELECT AN ANTIMICROBIAL (The Clinical Logic)

Before giving any antibiotic, you need to answer 6 questions:

What organism is causing the infection? - Gram stain + culture
Is the organism susceptible to the drug? - MIC (Minimum Inhibitory Concentration) testing
Where is the infection? - The drug must reach that site (e.g., some drugs don't cross into the CSF/brain)
What are the patient factors? - Age, pregnancy, kidney/liver function, immune status
Is the drug safe and effective? - Adverse effect profile
What is the cost? - Affordability and availability

Empiric vs Definitive Therapy

Empiric Therapy = you start antibiotics immediately based on clinical judgment BEFORE culture results come back. This is the most common scenario - you can't wait 48-72 hours for culture results when a patient is deteriorating.
Definitive Therapy = once culture + sensitivity results come, you narrow down to the most specific antibiotic.

PART 4: PHARMACODYNAMICS - HOW DO ANTIBIOTICS KILL?

Two Killing Patterns (Very Important for Dosing!)

1. Concentration-Dependent Killing

The more drug you give = the more bacteria you kill
Dosing strategy: Give a large single daily dose to create a high peak concentration
Examples: Aminoglycosides, Fluoroquinolones
Key parameter: Cmax/MIC ratio (peak concentration / minimum inhibitory concentration)

2. Time-Dependent Killing

It doesn't matter HOW HIGH the concentration is - what matters is how LONG the drug stays above the MIC
Dosing strategy: Give frequent small doses or continuous infusion
Examples: Penicillins, Cephalosporins
Key parameter: Time above MIC

3. Post-Antibiotic Effect (PAE)

Some antibiotics continue to suppress bacterial growth EVEN AFTER the drug concentration has fallen below the MIC
Aminoglycosides and Fluoroquinolones have a long PAE - this allows once-daily dosing

PART 5: THE MAJOR DRUG CLASSES - One by One

CLASS 1: BETA-LACTAM ANTIBIOTICS (The Biggest Family)

What makes them all "beta-lactam"? - They all share a 4-membered beta-lactam ring in their chemical structure. This ring is the business end - it is what attacks the bacteria.

Mechanism of Action:

Bacteria need to build their cell wall using an enzyme called transpeptidase (also called Penicillin-Binding Protein or PBP)
Beta-lactam drugs BIND to this PBP and BLOCK it - so the cell wall cannot be completed
Without a complete cell wall, bacteria undergo osmotic lysis (they swell and burst) - death!
This is why beta-lactams are bactericidal

A. PENICILLINS

The original and oldest antibiotic family. Discovered by Alexander Fleming.

Chemistry: Thiazolidine ring (A) + Beta-lactam ring (B) + amino group side chain. The 6-aminopenicillanic acid nucleus is essential for activity.

Groups of Penicillins:

1. Natural Penicillins (Penicillin G, Penicillin V)

Spectrum: Mainly gram-positive cocci (Streptococcus, Pneumococcus), Neisseria meningitidis, Treponema pallidum (syphilis)
Penicillin G - given IV, short half-life (30 min), needs dosing every 4 hours
- Benzathine Penicillin G = long-acting IM form - used for syphilis, rheumatic fever prophylaxis
- Procaine Penicillin G = medium-acting IM form
Penicillin V - oral form, but lower blood levels limit use
Uses: Streptococcal infections, meningococcal infections, neurosyphilis, rheumatic fever
Adverse Effects: Hypersensitivity (most common - from mild rash to anaphylactic shock), seizures at high doses

2. Anti-Staphylococcal Penicillins (Methicillin, Nafcillin, Oxacillin, Cloxacillin, Dicloxacillin)

Why needed? Many Staphylococci produce an enzyme called beta-lactamase that breaks the beta-lactam ring and inactivates ordinary penicillin. These drugs have bulky side chains that PROTECT the beta-lactam ring from this enzyme.
Spectrum: Mainly penicillinase-producing Staphylococci (MSSA)
Nafcillin/Oxacillin - IV use
Cloxacillin/Dicloxacillin - oral use
Important: They do NOT work against MRSA (Methicillin-Resistant Staphylococcus aureus) because MRSA changes the PBP itself (mecA gene encodes PBP-2a), making all beta-lactams ineffective

3. Extended-Spectrum / Aminopenicillins (Ampicillin, Amoxicillin)

Why extended? They have a free amino group on the side chain - this allows them to penetrate the outer membrane of gram-negative bacteria
Spectrum: Gram-positive + gram-negative (H. influenzae, E. coli, Salmonella, H. pylori)
Amoxicillin - better oral absorption than ampicillin (food does not affect it)
Uses: UTI, URTI, otitis media, typhoid, H. pylori eradication (with clarithromycin + PPI)
Amoxicillin-Clavulanate (Augmentin) - adding clavulanate (a beta-lactamase inhibitor) restores activity against beta-lactamase-producing organisms

4. Anti-Pseudomonal Penicillins (Piperacillin, Ticarcillin)

Broadest spectrum penicillins
Active against Pseudomonas aeruginosa (a notoriously resistant hospital bug)
Piperacillin/Tazobactam - the combination is widely used for hospital-acquired infections
Dose: 3.375-4.5 g IV every 4-6 hours

Beta-Lactamase Inhibitors (Clavulanic Acid, Sulbactam, Tazobactam, Avibactam)

These are NOT antibiotics themselves - they have no or weak antibacterial activity on their own
They SACRIFICE themselves to beta-lactamase - the enzyme destroys the inhibitor, leaving the antibiotic unharmed
Always given in combination: Amoxicillin + Clavulanate, Piperacillin + Tazobactam, Ampicillin + Sulbactam

B. CEPHALOSPORINS

Related to penicillins but more resistant to many beta-lactamases. Same mechanism (inhibit PBP). Organized into 5 Generations - each generation has progressively better gram-negative coverage but slightly reduced gram-positive activity.

Generation	Key Examples	Spectrum
1st Gen	Cefazolin (IV), Cephalexin (oral)	Gram-positive cocci, basic gram-negative (E. coli, Klebsiella, Proteus)
2nd Gen	Cefuroxime, Cefaclor, Cefoxitin	Extended gram-negative (H. influenzae), + anaerobes (cefoxitin, cefotetan)
3rd Gen	Ceftriaxone, Cefotaxime, Ceftazidime	Broad gram-negative, CNS penetration, Pseudomonas (ceftazidime)
4th Gen	Cefepime	Both gram-positive + gram-negative, Pseudomonas
5th Gen	Ceftaroline	Active against MRSA (only beta-lactam that covers MRSA!)

Memory Aid: "1st - Gram+, 2nd - More G-, 3rd - Best G- + CSF, 4th - Broad, 5th - MRSA"

Clinical Uses by Generation:

1st Gen Cefazolin = Gold standard for surgical prophylaxis (given 30-60 min before incision)
3rd Gen Ceftriaxone = Community-acquired pneumonia, meningitis, gonorrhea, typhoid
3rd Gen Ceftazidime = Pseudomonas infections
3rd Gen Ceftriaxone = Preferred in children for meningitis (excellent CSF penetration, once-daily dosing)

Important Points:

1st and 2nd gen: do NOT penetrate CNS - cannot treat meningitis
3rd gen and above: cross blood-brain barrier - can treat meningitis
Cross-allergy with penicillins: Only 1-2% of penicillin-allergic patients react to cephalosporins. Can use cephalosporins in mild penicillin allergy (rash); AVOID in immediate hypersensitivity (anaphylaxis).

C. CARBAPENEMS (Imipenem, Meropenem, Ertapenem, Doripenem)

Broadest spectrum beta-lactams - the last resort antibiotics in many cases
Resistant to most beta-lactamases
Imipenem is given with Cilastatin (a renal tubular enzyme inhibitor that prevents breakdown of imipenem in the kidney)
Spectrum: Almost everything - gram-positive, gram-negative, anaerobes, Pseudomonas
Uses: Severe hospital-acquired infections, polymicrobial infections, ESBL-producing organisms
Adverse effects: Seizures (especially imipenem in patients with renal failure or seizure history - meropenem is less epileptogenic)
Resistance: Carbapenem-Resistant Enterobacteriaceae (CRE) - a major public health threat

D. MONOBACTAMS (Aztreonam)

Only active against aerobic gram-negative bacteria (including Pseudomonas)
No activity against gram-positives or anaerobes
Key advantage: Safe in patients with penicillin allergy - structurally distinct, no cross-reactivity
Used for gram-negative infections in penicillin-allergic patients

E. VANCOMYCIN (Not a beta-lactam, but a cell wall inhibitor)

Inhibits cell wall synthesis by binding to D-Ala-D-Ala terminal of peptidoglycan precursors - a different step than beta-lactams
Spectrum: Gram-positive ONLY (especially MRSA, Enterococcus)
The drug of choice for MRSA
"Red Man Syndrome" - if infused too fast, causes flushing, erythema, and hypotension due to histamine release. Prevented by slow infusion over 60 minutes.
Adverse Effects: Nephrotoxicity, ototoxicity (especially with aminoglycosides)
Monitoring: Serum trough levels must be monitored

CLASS 2: AMINOGLYCOSIDES (Gentamicin, Amikacin, Tobramycin, Streptomycin, Neomycin)

Mechanism: Bind irreversibly to the 30S ribosomal subunit - they cause misreading of the genetic code, producing abnormal proteins, and also disrupt the bacterial cell membrane. This is why they are bactericidal (unlike other 30S inhibitors like tetracyclines which are bacteriostatic).

How they get inside the cell: Aminoglycosides require active oxygen-dependent transport across the bacterial membrane. This is why they do NOT work against anaerobes (no oxygen transport).

Spectrum: Gram-negative aerobic rods (E. coli, Klebsiella, Pseudomonas, Proteus). Streptomycin also covers Mycobacteria and Brucella.

Concentration-Dependent Killing + Long PAE = Once-daily dosing (one large dose) is the modern approach.

Adverse Effects (The Big Three - Must Know!):

Nephrotoxicity - reversible, affects proximal tubules. Risk increased by volume depletion, other nephrotoxic drugs.
Ototoxicity - both cochlear (hearing loss, irreversible) and vestibular (balance problems). Aminoglycosides accumulate in the inner ear fluid.
Neuromuscular Blockade - at very high doses, can cause respiratory paralysis (important in patients on muscle relaxants or with myasthenia gravis)

Monitoring: Serum drug levels (peak and trough) are mandatory.

Clinical Uses:

Gentamicin - gram-negative hospital infections (often combined with beta-lactams for synergy)
Amikacin - reserved for gentamicin-resistant organisms
Streptomycin - tuberculosis (second-line), plague, brucellosis, tularemia
Neomycin - topical use only, bowel sterilization before surgery (not absorbed orally)
Tobramycin - Pseudomonas (especially in cystic fibrosis, as inhaled tobramycin)

Synergy with Penicillins: Aminoglycosides + Penicillin together kill Enterococcus synergistically - neither drug alone is bactericidal for Enterococcus, but together they are. The penicillin disrupts the cell wall (allowing aminoglycoside to enter more easily).

CLASS 3: TETRACYCLINES (Tetracycline, Doxycycline, Minocycline, Tigecycline)

Mechanism: Bind reversibly to the 30S ribosomal subunit, blocking the attachment of aminoacyl-tRNA to the mRNA-ribosome complex. This prevents new amino acids from being added - protein synthesis stops. Bacteriostatic.

Spectrum: Broad spectrum - gram-positive, gram-negative, atypicals (Mycoplasma, Chlamydia, Rickettsia), spirochetes.

Doxycycline is the most clinically important tetracycline - better oral absorption, longer half-life, more lipophilic.

Clinical Uses (Think "MRCAST"):

Mycoplasma pneumonia
Rickettsia (Rocky Mountain spotted fever)
Chlamydia (STIs, PID, psittacosis, trachoma)
Acne vulgaris (long-term doxycycline)
Spirochetes - Lyme disease (Borrelia) - Doxycycline is drug of choice
Tularemia, Brucellosis, Cholera

Adverse Effects:

GI disturbance - nausea, vomiting, diarrhea (take with food, but not with milk/antacids)
Teeth staining and bone growth inhibition in children under 8 - tetracyclines bind calcium, depositing in developing teeth and bones. Permanent yellow-gray discoloration.
Photosensitivity - sunburn easily while on tetracyclines
Fanconi syndrome - outdated tetracycline is nephrotoxic
Esophageal ulceration - take with plenty of water, remain upright

Contraindications: Children under 8, pregnancy, lactation

Interaction: Chelation with Ca²⁺, Mg²⁺, Al³⁺, Fe²⁺ (antacids, dairy, iron tablets) dramatically reduces absorption. Take 2 hours apart.

Tigecycline - newer, IV only, works against MRSA and multi-drug resistant organisms. Derived from minocycline.

CLASS 4: MACROLIDES (Erythromycin, Azithromycin, Clarithromycin, Roxithromycin)

Mechanism: Bind to the 50S ribosomal subunit (specifically 23S rRNA), blocking the translocation step of protein synthesis. Bacteriostatic (bactericidal at high concentrations).

Spectrum: Gram-positive cocci, atypical organisms (Mycoplasma, Chlamydia, Legionella, Campylobacter, H. pylori), some mycobacteria.

Erythromycin - the original macrolide. Poor GI tolerance (stimulates motilin receptors - causes nausea, vomiting, abdominal cramps). Inhibits CYP3A4 - major drug interactions. Used for motility disorders (prokinetic at low doses).

Azithromycin (Z-Pack) - The most prescribed. Extremely long tissue half-life (68 hours!), so only 5 days of treatment needed. Minimal CYP inhibition. Best for community-acquired pneumonia (covers both typical and atypical organisms), Chlamydia (single 1g dose), traveller's diarrhea.

Clarithromycin - Best for H. pylori eradication (combined with amoxicillin + PPI = "triple therapy"). Also for MAC (Mycobacterium avium complex) in HIV patients.

Cardiac Toxicity: All macrolides can prolong QTc interval - risk of torsades de pointes. Caution with other QT-prolonging drugs.

CLASS 5: CHLORAMPHENICOL

Mechanism: Binds to 50S ribosomal subunit, inhibits the enzyme peptidyl transferase - prevents peptide bond formation. Bacteriostatic (bactericidal against Haemophilus, Pneumococcus, Meningococcus).

Spectrum: Very broad - gram-positive, gram-negative, anaerobes, Rickettsia. Excellent CNS penetration.

Adverse Effects (The Critical Ones):

Aplastic Anemia - the most feared. Rare (1 in 25,000-40,000) but IRREVERSIBLE. Idiosyncratic reaction - not dose-related. Causes death. This has severely limited its use.
Grey Baby Syndrome - in neonates/premature infants. They lack the glucuronyl transferase enzyme to conjugate chloramphenicol. Drug accumulates - causes vomiting, abdominal distension, grey color, cardiovascular collapse, death. Contraindicated in neonates.
Bone marrow suppression - dose-related, reversible. Monitor CBC during therapy.

Uses today: Limited to meningitis (especially when other drugs fail or patient is allergic to beta-lactams), typhoid fever (in developing countries), rickettsial infections (when doxycycline contraindicated), brain abscess.

CLASS 6: CLINDAMYCIN

Mechanism: Binds 50S ribosome, similar to macrolides. Bacteriostatic.

Spectrum: Gram-positive cocci (Staphylococci, Streptococci), ANAEROBES (its strongest suit - especially Bacteroides fragilis).

Big advantage: Excellent for anaerobic infections (dental infections, lung abscess, intra-abdominal sepsis, pelvic inflammatory disease).

Uses: Skin and soft tissue infections, bone infections (excellent bone penetration), pelvic infections, anaerobic pulmonary infections, toxoplasma (with pyrimethamine in AIDS patients).

Key Adverse Effect: Pseudomembranous Colitis (C. difficile colitis) - Clindamycin is the CLASSIC cause. By killing normal bowel flora, it allows Clostridioides difficile (which produces a toxin) to overgrow. Presents as severe bloody diarrhea. Treat with oral Vancomycin or Metronidazole or Fidaxomicin.

CLASS 7: FLUOROQUINOLONES (Ciprofloxacin, Levofloxacin, Moxifloxacin, Ofloxacin, Norfloxacin)

Mechanism: Inhibit bacterial DNA gyrase (Topoisomerase II) and Topoisomerase IV. DNA gyrase uncoils the supercoiled DNA so it can be replicated - blocking it causes DNA strand breaks and bacterial death. Bactericidal. Concentration-dependent killing.

Spectrum:

Ciprofloxacin - best anti-Pseudomonas activity among oral antibiotics; gram-negative focus
Levofloxacin - extended gram-positive coverage; "respiratory quinolone" (covers Streptococcus pneumoniae)
Moxifloxacin - best anaerobic coverage; "respiratory quinolone"

Clinical Uses:

UTI (especially complicated, or resistant organisms)
Respiratory tract infections (levofloxacin/moxifloxacin for community-acquired pneumonia)
Anthrax prophylaxis/treatment
Typhoid fever
Tuberculosis (second-line)
Pseudomonas infections
Gonorrhoea (but resistance is increasing)
Traveller's diarrhea

Adverse Effects:

Tendinopathy and tendon rupture - especially Achilles tendon. Risk increased in elderly, steroid users. Black box warning.
CNS effects - headache, dizziness, insomnia, rarely seizures and psychosis
QTc prolongation - cardiac arrhythmias
Photosensitivity
Cartilage/Joint damage in growing animals - hence avoid in children and pregnancy (theoretical, but caution maintained)
Hyperglycemia/hypoglycemia - especially with diabetic medications

Drug Interactions: Chelated by antacids, Ca²⁺, Mg²⁺, Fe²⁺ (take 2 hours apart). Increases theophylline levels.

CLASS 8: SULFONAMIDES (Sulfamethoxazole, Sulfadiazine, Sulfacetamide)

Mechanism: Bacteria cannot absorb folic acid from outside - they MUST synthesize it from PABA (para-aminobenzoic acid). Sulfonamides are structural analogs of PABA. They competitively inhibit dihydropteroate synthase, blocking folate synthesis. Without folate, bacteria cannot make purines, and DNA synthesis stops. Bacteriostatic.

Human cells are NOT affected because humans get folate from food (we don't synthesize it ourselves). This is the basis of selective toxicity.

Trimethoprim (TMP) works at the NEXT STEP - it inhibits dihydrofolate reductase, blocking conversion of dihydrofolate to tetrahydrofolate. Also bacteriostatic alone.

TMP-SMX (Cotrimoxazole = Trimethoprim + Sulfamethoxazole) - The gold standard combination. Sequential blockade of folate pathway at TWO points = synergistic bactericidal effect.

Uses of TMP-SMX:

UTI - most common indication. Drug of choice for uncomplicated UTI where organism is susceptible.
PCP (Pneumocystis jirovecii Pneumonia) - drug of choice in HIV/AIDS patients (both treatment and prophylaxis)
Shigellosis, Salmonellosis
Toxoplasmosis (with pyrimethamine)
MRSA skin infections (TMP-SMX is surprisingly effective)
Nocardiosis

Adverse Effects of Sulfonamides:

Hypersensitivity - rash, fever, Stevens-Johnson syndrome (severe, life-threatening skin reaction)
Kernicterus in neonates - sulfonamides displace bilirubin from albumin, causing bilirubin to deposit in infant's brain. Contraindicated in neonates and near term pregnancy.
Hemolytic anemia in G6PD-deficient patients
Crystalluria - crystals form in urine, blocking kidney tubules. Prevent by drinking plenty of water and alkalinizing urine.
Bone marrow suppression

CLASS 9: RIFAMPICIN (Rifampin)

Mechanism: Inhibits bacterial DNA-dependent RNA polymerase (the enzyme that copies DNA into RNA). Binds to the beta subunit of prokaryotic RNA polymerase - completely different from the mammalian enzyme (selective toxicity). Bactericidal.

Most important use: Tuberculosis - first-line drug (HRZE regimen: isoniazid + Rifampicin + Pyrazinamide + Ethambutol)

Also used for:

Leprosy (in combination regimens)
Meningococcal prophylaxis (contacts of meningitis patients)
MRSA (always in combination - never alone due to rapid resistance development)
Brucellosis

Orange discoloration: Rifampicin turns urine, tears, saliva, sweat, and contact lenses orange-red. Warn patients! This is harmless but alarming.

Drug Interactions - CRITICAL: Rifampicin is a POTENT INDUCER of CYP450 enzymes (especially CYP3A4, CYP2C9). This dramatically increases the metabolism of:

Oral contraceptives (use barrier contraception!)
Warfarin (increase dose during rifampicin therapy)
HIV antiretrovirals
Corticosteroids
Many other drugs

Adverse Effects: Hepatotoxicity (monitor liver function tests), GI disturbance, flu-like syndrome with intermittent dosing.

CLASS 10: METRONIDAZOLE (The Anaerobe Killer + Antiprotozoal)

Mechanism: A prodrug. Inside anaerobic organisms and certain parasites, ferredoxin reduces metronidazole to a toxic intermediate that damages bacterial DNA. Aerobic organisms cannot activate metronidazole. Bactericidal against anaerobes.

Spectrum: Anaerobic bacteria (Bacteroides fragilis, Clostridium), protozoa (Giardia, Entamoeba histolytica, Trichomonas vaginalis).

Uses:

Anaerobic infections (intra-abdominal, pelvic, dental, brain abscess)
C. difficile colitis (oral metronidazole, though vancomycin is now preferred for severe cases)
Giardiasis (drug of choice)
Amoebiasis (drug of choice for invasive, systemic amoeba - but not luminal - add diloxanide furoate)
Trichomoniasis (treat both partners!)
H. pylori eradication (in combination regimens)
Bacterial vaginosis

Adverse Effects:

Disulfiram-like reaction with alcohol - MUST warn patients to avoid alcohol completely during therapy and 48 hours after (causes severe flushing, nausea, vomiting, headache)
Metallic taste in mouth
Peripheral neuropathy (with prolonged use)
CNS effects (dizziness, headache)
Nausea, GI upset

PART 6: ANTIMICROBIAL RESISTANCE - The Modern Crisis

Bacteria are smart. They develop resistance through several mechanisms:

Mechanism	How	Example
Beta-lactamase production	Enzyme destroys the antibiotic	ESBL-producing E. coli
Altered target site	Change PBP so antibiotic cannot bind	MRSA (altered PBP-2a, mecA gene)
Efflux pumps	Pump the drug out of the cell faster than it enters	Pseudomonas, tetracycline resistance
Decreased permeability	Alter outer membrane porins - drug can't get in	Gram-negative resistance
Enzymatic modification	Acetylation, phosphorylation of drug	Aminoglycoside resistance
Target bypass	Develop alternative pathway	Vancomycin-resistant Enterococcus (VRE) - changes D-Ala-D-Ala to D-Ala-D-Lactate

MRSA specifically: Carries mecA gene → encodes PBP-2a (altered protein that doesn't bind beta-lactams). Only ceftaroline (5th-gen cephalosporin) among beta-lactams can bind PBP-2a. Vancomycin and linezolid are mainstays.

PART 7: DRUG COMBINATIONS IN ANTIMICROBIALS

When to combine?

Reason	Example
Synergy (1+1 = 3 effect)	Penicillin + Aminoglycoside for Enterococcal endocarditis
Prevent resistance	TB treatment (HRZE - if you use one drug alone, resistance develops within weeks)
Broaden spectrum (empiric therapy in serious infections)	Ceftriaxone + Metronidazole for intra-abdominal infection
Beta-lactamase inhibition	Amoxicillin + Clavulanate

When NOT to combine (antagonism):

Bacteriostatic + Bactericidal can ANTAGONIZE each other
Classic example: Tetracyclines/Chloramphenicol (bacteriostatic) + Penicillin (bactericidal) - the static drug prevents bacterial growth, so penicillin (which needs actively growing cells to work) becomes ineffective

PART 8: SPECIAL PATIENT CONSIDERATIONS

As a doctor, you must always adjust based on:

Patient Factor	Impact
Renal failure	Dose-reduce or avoid aminoglycosides, vancomycin, fluoroquinolones
Hepatic failure	Reduce rifampicin, doxycycline, chloramphenicol, metronidazole
Pregnancy	Safe: Penicillins, Cephalosporins, Azithromycin. Avoid: Tetracyclines, Fluoroquinolones, Aminoglycosides, Sulfonamides (near term), Metronidazole (1st trimester)
Neonates	Avoid Chloramphenicol (Grey Baby syndrome), Sulfonamides (Kernicterus)
Children < 8 years	Avoid Tetracyclines (teeth/bones)
Immunocompromised	Always use bactericidal drugs; longer courses needed
G6PD deficiency	Avoid sulfonamides, nitrofurantoin, primaquine (hemolysis)

PART 9: COMPLICATIONS OF ANTIMICROBIAL THERAPY - Summary

Hypersensitivity - most with penicillins. Spectrum from rash → urticaria → anaphylaxis → Stevens-Johnson syndrome
Superinfection - killing normal flora allows resistant organisms to overgrow. Classic example: C. difficile after clindamycin; Candida oral thrush after broad-spectrum antibiotics
Organ toxicity - kidney (aminoglycosides, vancomycin), liver (rifampicin, isoniazid), bone marrow (chloramphenicol), ear (aminoglycosides), tendon (fluoroquinolones)
Drug interactions - especially rifampicin (CYP inducer) and erythromycin/azithromycin (CYP inhibitors)

PART 10: QUICK MEMORY TABLES FOR EXAMS

"Drugs to Avoid in Pregnancy" - FAST MNEMONIC

"MATT is not safe in pregnancy"

M - Metronidazole (1st trimester)
A - Aminoglycosides
T - Tetracyclines
T - TMP-SMX (near term - kernicterus)
Plus Fluoroquinolones, Chloramphenicol

Sites of Action - Quick Reference

CELL WALL:         Beta-lactams (Penicillin, Cephalosporins, Carbapenems)
                   Vancomycin, Bacitracin, Cycloserine

CELL MEMBRANE:     Polymyxins, Amphotericin B (antifungal)

30S RIBOSOME:      Aminoglycosides (bactericidal)
                   Tetracyclines (bacteriostatic)

50S RIBOSOME:      Macrolides, Chloramphenicol, Clindamycin, Linezolid

DNA GYRASE:        Fluoroquinolones

RNA POLYMERASE:    Rifampicin

FOLATE SYNTHESIS:  Sulfonamides (DHPS step)
                   Trimethoprim (DHFR step)

DNA DAMAGE:        Metronidazole, Nitrofurantoin

The "Last Resort" Antibiotics

When everything else fails:

MRSA: Vancomycin, Linezolid, Daptomycin, Ceftaroline, Teicoplanin
VRE: Linezolid, Daptomycin
Pseudomonas: Ceftazidime, Ciprofloxacin, Piperacillin-Tazobactam, Meropenem, Colistin
CRE/Pan-resistant: Colistin (Polymyxin E), Tigecycline - the absolute last resorts

Sources: Katzung's Basic and Clinical Pharmacology, 16th Edition (Chapters 43-47) and Lippincott Illustrated Reviews: Pharmacology (Unit VI, Chapters 28-36). These cover the same core content as Gobind Rai Garg and Bhalani Pharmacology used in Indian medical colleges - the mechanisms, classifications, and clinical points are identical across all standard pharmacology texts.

That is your complete antimicrobial pharmacology lecture. Every major drug class is covered - mechanism, spectrum, clinical uses, adverse effects, and the clinical logic behind why we use what we use. This is the depth you need for both university exams and clinical practice. If you want me to go even deeper into any single class (e.g., full anti-TB drugs, antifungals, antivirals), just ask!

Fosfomycin bacitaracin and cycloserine and vancomyin belongs to which group and placed under which Classification heading and subheading

Quick answer: All four drugs - Fosfomycin, Bacitracin, Cycloserine, and Vancomycin - belong to the group of Cell Wall Synthesis Inhibitors, but each works at a different STEP of cell wall synthesis. They are classified under "Other Cell Wall-Active Antibiotics" (separate from beta-lactams).

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Fosfomycin, Bacitracin, Cycloserine & Vancomycin - Exact Classification

The Big Picture First

All four drugs belong to the same broad group - they all inhibit bacterial cell wall synthesis. But they are NOT beta-lactams. They form a separate subgroup called "Other Cell Wall-Active Antibiotics" or "Non-Beta-Lactam Cell Wall Inhibitors".

The Complete Classification Tree

GROUP: ANTIMICROBIAL DRUGS
│
├── CLASS: CELL WALL SYNTHESIS INHIBITORS
│   │
│   ├── SUBGROUP A: BETA-LACTAM DRUGS (Penicillins, Cephalosporins,
│   │               Carbapenems, Monobactams)
│   │
│   └── SUBGROUP B: OTHER CELL WALL-ACTIVE ANTIBIOTICS
│       │
│       ├── Glycopeptides ──────────────► VANCOMYCIN
│       │
│       ├── Phosphonic acid derivative ──► FOSFOMYCIN
│       │
│       ├── Cyclic peptide ──────────────► BACITRACIN
│       │
│       └── D-Alanine analog ────────────► CYCLOSERINE

In Katzung, this entire group is covered under Chapter 43: "Beta-Lactam & Other Cell Wall- & Membrane-Active Antibiotics" - so the chapter heading itself tells you the classification.

In Lippincott, they appear in the "Agents Affecting Cell Wall Synthesis" chapter, under "Other Antibiotics" alongside Vancomycin, Daptomycin, and Colistin.

Now Each Drug - Its Exact Subclass, Heading, and Mechanism

1. VANCOMYCIN


Classification Heading	Cell Wall Synthesis Inhibitors
Subheading / Subclass	Glycopeptide Antibiotics
Chemical Nature	Tricyclic glycopeptide (large molecular weight)
Step Blocked	Late step - binds to the D-Ala-D-Ala terminus of peptidoglycan precursors, blocking transglycosylase - prevents elongation and cross-linking of peptidoglycan chains

Think of it this way: Penicillin blocks the FINAL cross-linking step (transpeptidation). Vancomycin blocks the step JUST BEFORE that - it grabs the building blocks before they can even be connected.

Other Glycopeptides in the same subgroup: Teicoplanin, Telavancin, Dalbavancin, Oritavancin.

2. FOSFOMYCIN


Classification Heading	Cell Wall Synthesis Inhibitors
Subheading / Subclass	Phosphonic Acid Derivative (or "Miscellaneous Cell Wall Inhibitors")
Chemical Nature	Analog of phosphoenolpyruvate (PEP) - structurally unrelated to ANY other antimicrobial
Step Blocked	The VERY FIRST STEP of cell wall synthesis

Mechanism in detail: Fosfomycin inhibits the enzyme enolpyruvate transferase (MurA) by covalently binding to its cysteine residue. This enzyme catalyzes the very first committed step - the addition of phosphoenolpyruvate to UDP-N-acetylglucosamine (UDP-NAG) to form UDP-N-acetylmuramic acid (UDP-NAM).

In plain language: UDP-NAM is the most basic building block of the peptidoglycan wall. Fosfomycin stops you from even making that building block. No building blocks = no wall.

3. BACITRACIN


Classification Heading	Cell Wall Synthesis Inhibitors
Subheading / Subclass	Cyclic Peptide Antibiotic (or "Polypeptide Antibiotic")
Chemical Nature	Cyclic peptide mixture from Bacillus subtilis (Tracy strain, 1943)
Step Blocked	Intermediate step - the lipid carrier recycling step

Mechanism in detail: In cell wall synthesis, peptidoglycan subunits are assembled inside the cell and then carried across the membrane to the outside by a lipid carrier molecule (undecaprenyl pyrophosphate). After delivering its cargo, this carrier must be dephosphorylated (recycled) to be used again. Bacitracin inhibits this dephosphorylation/recycling of the lipid carrier. The carrier gets stuck in its used-up form, so no more peptidoglycan subunits can be transported outside.

Analogy: Imagine a conveyor belt delivering bricks for a wall. Bacitracin jams the conveyor belt's return mechanism - bricks pile up inside and can never reach the wall.

4. CYCLOSERINE


Classification Heading	Cell Wall Synthesis Inhibitors
Subheading / Subclass	D-Alanine Analog (or "Miscellaneous Cell Wall Inhibitors")
Chemical Nature	Structural analog of D-alanine, produced by Streptomyces orchidaceus
Step Blocked	Early cytoplasmic step - incorporation of D-alanine into peptidoglycan

Mechanism in detail: The peptidoglycan pentapeptide chain requires D-alanine to be added to it. To get D-alanine, bacteria must:

Step 1: Convert L-alanine → D-alanine (enzyme: alanine racemase)
Step 2: Join two D-alanines together as D-Ala-D-Ala (enzyme: D-Ala-D-Ala ligase)

Cycloserine inhibits BOTH of these enzymes (competitive inhibitor, since it structurally resembles D-alanine). No D-Ala-D-Ala = incomplete peptidoglycan chain = weak/no cell wall.

Summary Table (Exam-Ready)

Drug	Subclass	Step Blocked in Cell Wall Synthesis
Vancomycin	Glycopeptide	Binds D-Ala-D-Ala of peptidoglycan precursor - blocks transglycosylase (late step)
Fosfomycin	Phosphonic acid derivative	Inhibits MurA (enolpyruvate transferase) - FIRST step, blocks UDP-NAM formation
Bacitracin	Cyclic peptide (Polypeptide)	Blocks dephosphorylation of lipid carrier - prevents recycling of undecaprenyl pyrophosphate
Cycloserine	D-Alanine analog	Inhibits alanine racemase + D-Ala-D-Ala ligase - blocks D-alanine incorporation

The 3 Steps of Cell Wall Synthesis & Which Drug Blocks Which

STEP 1 (Cytoplasm - Early):
   UDP-NAG  ──[MurA]──► UDP-NAM
              ▲
              FOSFOMYCIN blocks here

STEP 2 (Cytoplasm - Middle):
   L-Ala ──[racemase]──► D-Ala ──[ligase]──► D-Ala-D-Ala
              ▲                         ▲
              CYCLOSERINE blocks both these enzymes

STEP 3 (Membrane - Transport):
   Lipid carrier transports subunits across membrane,
   then gets recycled (dephosphorylated)
              ▲
              BACITRACIN blocks the recycling

STEP 4 (Outside membrane - Final):
   Cross-linking of peptidoglycan chains
              ▲
              VANCOMYCIN blocks transglycosylase (grabs D-Ala-D-Ala)
              PENICILLINS/CEPHALOSPORINS block transpeptidase

Quick Memory Aid

"For Bad Cells Vanish" - Fosfomycin, Bacitracin, Cycloserine, Vancomycin = all wall blockers, NOT beta-lactams.

Or remember by the step:

Fosfomycin = First step
Bacitracin = Bridge step (carrier transport)
Cycloserine = Cytoplasmic step (D-Ala)
Vancomycin = Very last cross-linking step (pre-transpeptidation)

Sources: Katzung's Basic and Clinical Pharmacology 16th Ed, Chapter 43 "Beta-Lactam & Other Cell Wall- & Membrane-Active Antibiotics"; Lippincott Illustrated Reviews Pharmacology, Chapter 29 "Agents Affecting Cell Wall Synthesis"

Can you Classify all antimicrobials-which are divided in to antibiotics,antivirals,antifungal,antiparasitic,anti-helminthics and every anti drugs,it's first heafing ,sub heading,which group it belongs to ,mode of action-explain it in one line simplest way to learn and remember it ,uses,Contraindications,in which disease or disorders to give it and for many days,in od or bdor tds or qid,how many tablets and in which form capsules or tab or syrup or other forms,initial dose,maintainenxe dose,explain me standard dosing,I'm or iv ,calculations how much to give ,opd basis and ipd basis too..explain

This is an extremely large request covering every antimicrobial class with full dosing details. Let me clarify scope before diving in so I give you exactly what's most useful.

Asking for Preferences

Perfect. Final year / Internship level, all classes, mix of tables + explanation. Let me pull everything from the textbooks now.

Finding Sources

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I now have all the textbook data I need. Here is the complete, final-year level reference covering every antimicrobial class.

COMPLETE ANTIMICROBIAL DRUG REFERENCE

Final Year MBBS / Internship Edition

Sources: Katzung 16th Ed + Lippincott Pharmacology

MASTER CLASSIFICATION TREE

ANTIMICROBIAL DRUGS
├── A. ANTIBIOTICS (Antibacterials)
│   ├── 1. Cell Wall Synthesis Inhibitors
│   │   ├── Beta-Lactams: Penicillins, Cephalosporins, Carbapenems, Monobactams
│   │   └── Non-Beta-Lactams: Vancomycin, Fosfomycin, Bacitracin, Cycloserine
│   ├── 2. Cell Membrane Disruptors: Polymyxins, Daptomycin
│   ├── 3. Protein Synthesis Inhibitors
│   │   ├── 30S: Aminoglycosides, Tetracyclines
│   │   └── 50S: Macrolides, Chloramphenicol, Clindamycin, Linezolid
│   ├── 4. DNA/RNA Synthesis Inhibitors: Fluoroquinolones, Rifampicin, Metronidazole
│   ├── 5. Folate Synthesis Inhibitors: Sulfonamides, Trimethoprim
│   └── 6. Antimycobacterials: Anti-TB drugs, Anti-leprosy drugs
├── B. ANTIFUNGALS
│   ├── Polyenes: Amphotericin B, Nystatin
│   ├── Azoles: Fluconazole, Itraconazole, Voriconazole, Ketoconazole
│   ├── Echinocandins: Caspofungin, Micafungin
│   └── Others: Flucytosine, Griseofulvin, Terbinafine
├── C. ANTIVIRALS
│   ├── Anti-herpes: Acyclovir, Valacyclovir, Ganciclovir
│   ├── Anti-HIV (ARTs): NRTIs, NNRTIs, PIs, Integrase inhibitors
│   ├── Anti-Influenza: Oseltamivir, Zanamivir
│   └── Anti-Hepatitis: Sofosbuvir, Entecavir, Tenofovir
├── D. ANTIPROTOZOALS
│   ├── Antimalarials: Chloroquine, Artemisinin, Quinine, Primaquine
│   ├── Antiamoebics: Metronidazole, Diloxanide furoate
│   ├── Antileishmaniasis: Amphotericin B, Miltefosine
│   └── Others: Metronidazole (Giardia), Tinidazole, Pentamidine
└── E. ANTIHELMINTHICS
    ├── Benzimidazoles: Albendazole, Mebendazole
    ├── Imidazothiazoles: Levamisole
    ├── Tetrahydropyrimidines: Pyrantel pamoate
    ├── Macrocyclic lactones: Ivermectin
    └── Others: Praziquantel, Diethylcarbamazine (DEC), Niclosamide

SECTION A: ANTIBIOTICS

1. CELL WALL SYNTHESIS INHIBITORS - BETA-LACTAMS

1A. PENICILLINS

Heading: Cell Wall Synthesis Inhibitors > Beta-Lactam Antibiotics > Penicillins MOA (one line): Block PBP (transpeptidase) enzyme - prevent final cross-linking of peptidoglycan - cell wall breaks - bacteria lyse and die (BACTERICIDAL)

PENICILLIN G (Benzylpenicillin)

Parameter	Detail
Form	Injection only (IV/IM) - no oral form (destroyed by stomach acid)
Dose	1-4 million units IV every 4-6 hours
OPD	NOT used (IV only)
IPD	Yes - IV infusion
Loading dose	None - start standard dose directly
Maintenance	1-4 MU q4-6h IV
Duration	Pneumonia: 7-10 days; Meningitis: 10-14 days; Syphilis: as per protocol
Uses	Streptococcal infections, pneumococcal meningitis, neurosyphilis, gas gangrene, actinomycosis, rheumatic fever (prophylaxis)
Contraindications	Penicillin hypersensitivity/allergy; anaphylaxis history
Special Notes	Half-life only 30 min - must dose every 4 hours strictly

Benzathine Penicillin G (Long-acting IM):

1.2 million units IM single dose - for syphilis (primary/secondary), rheumatic fever prophylaxis
Releases slowly over 2-4 weeks - ONE INJECTION is enough
OPD use - patient comes once, gets injected, done

PENICILLIN V (Phenoxymethylpenicillin)

Parameter	Detail
Form	Oral tablets 250 mg, 500 mg; Syrup 125 mg/5 mL
Dose	250-500 mg PO every 6 hours (QID)
Frequency	QID (every 6 hours)
Duration	Strep throat: 10 days; Skin infections: 7-10 days
OPD	Yes - oral, commonly used
IPD	Rarely (prefer Pen G IV for serious cases)
Uses	Minor streptococcal infections, dental infections, prophylaxis in asplenic patients
Contraindications	Penicillin allergy
Food	Take on empty stomach (1 hour before or 2 hours after food - except amoxicillin)

AMPICILLIN

Parameter	Detail
Form	Capsules 250 mg, 500 mg; Powder for injection 250 mg, 500 mg, 1g; Syrup 125 mg/5 mL
Oral dose	250-500 mg QID (every 6 hours)
IV dose	1-2 g IV every 4-6 hours
OPD	Yes - oral capsules
IPD	Yes - IV for serious infections
Duration	UTI: 7 days; Meningitis: 14-21 days; Typhoid: 14 days
Uses	UTI, URTI, otitis media, meningitis (Listeria), typhoid (less preferred now), H. pylori combination
Contraindications	Penicillin allergy; mononucleosis (causes rash in 100% of cases - avoid)

AMOXICILLIN ⭐ (Most prescribed oral antibiotic)

Parameter	Detail
Form	Capsules/Tablets 250 mg, 500 mg, 875 mg; Syrup 125 mg/5 mL, 250 mg/5 mL
Adult dose	250-500 mg TDS (every 8 hours)
High dose	875 mg BD or 1g TDS for resistant organisms
Pediatric dose	20-40 mg/kg/day divided TDS
Frequency	TDS (food does not affect absorption - can take with food)
OPD	Yes - most common outpatient antibiotic
Duration	URTI: 5-7 days; Otitis media: 10 days; Pneumonia: 7-10 days; H. pylori: 7-14 days
Uses	URTI, LRTI, otitis media, sinusitis, dental infections, H. pylori eradication, Lyme disease (early), UTI
Contraindications	Penicillin allergy, mononucleosis

AMOXICILLIN + CLAVULANATE (Augmentin) ⭐

Parameter	Detail
Form	Tablets 375 mg (250+125), 625 mg (500+125), 1g (875+125); Syrup 228 mg/5 mL
Adult dose	625 mg TDS or 1g BD
Pediatric dose	20-40 mg/kg/day (amoxicillin component) TDS
Frequency	TDS (625 mg) or BD (1g)
OPD	Yes - very commonly prescribed
Duration	5-7 days for most infections; 10-14 days for severe
Uses	Skin infections, bite wounds, dental abscess, sinusitis, LRTI, UTI with resistant organisms
Contraindications	Penicillin allergy; jaundice/hepatic dysfunction from previous augmentin use
Why add clavulanate?	Clavulanate inhibits beta-lactamase - restores activity against resistant organisms

PIPERACILLIN + TAZOBACTAM (Pip-Tazo)

Parameter	Detail
Form	Injection only: 4.5 g vial (4g pip + 0.5g tazo)
Adult dose	4.5 g IV every 6-8 hours; severe: every 4-6 hours
OPD	NO - IV only
IPD	Yes - ICU/ward
Duration	7-14 days depending on infection
Uses	Hospital-acquired pneumonia, intra-abdominal infections, severe UTI, sepsis, Pseudomonas infections
Contraindications	Penicillin allergy

1B. CEPHALOSPORINS - By Generation

Heading: Cell Wall Synthesis Inhibitors > Beta-Lactam Antibiotics > Cephalosporins MOA (one line): Same as penicillins - bind PBP, block cell wall transpeptidation - bactericidal; but more resistant to beta-lactamase than penicillins

FIRST GENERATION

CEFAZOLIN (IV) - Gold standard surgical prophylaxis

Parameter	Detail
Form	Injection: 500 mg, 1 g, 2 g vials
Surgical prophylaxis	1-2 g IV single dose 30-60 min before incision
Treatment dose	1-2 g IV every 8 hours
OPD	NO
IPD	Yes
Duration	Prophylaxis: single dose; Infections: 7-14 days
Uses	SURGICAL PROPHYLAXIS (most important use), MSSA skin infections, UTI, soft tissue infections
Contraindications	Cephalosporin allergy; anaphylaxis to penicillin

CEPHALEXIN (Cefalexin) - Oral, 1st Gen

Parameter	Detail
Form	Capsules 250 mg, 500 mg; Syrup 125 mg/5 mL, 250 mg/5 mL
Adult dose	250-500 mg QID (every 6 hours)
Pediatric	25-50 mg/kg/day divided QID
OPD	Yes
Duration	Skin infections: 7-10 days; UTI: 7 days
Uses	MSSA skin and soft tissue infections, UTI, minor strep infections
Contraindications	Cephalosporin/severe penicillin allergy

SECOND GENERATION

CEFUROXIME

Parameter	Detail
Form	Tablets 250 mg, 500 mg; Injection 750 mg, 1.5 g
Oral dose	250-500 mg BD
IV dose	750 mg-1.5 g IV every 8 hours
OPD	Yes (oral)
IPD	Yes (IV)
Duration	7-10 days
Uses	URTI, otitis media, sinusitis, community-acquired pneumonia (CAP), UTI, Lyme disease
Contraindications	Cephalosporin allergy

THIRD GENERATION - Most clinically important

CEFTRIAXONE ⭐ (The Workhorse Cephalosporin)

Parameter	Detail
Form	Injection: 250 mg, 500 mg, 1 g, 2 g vials
Standard adult dose	1-2 g IV/IM OD (once daily - longest half-life among cephalosporins ~8 hrs)
Meningitis dose	2 g IV BD (every 12 hours)
Gonorrhea	500 mg IM single dose
Pediatric	50-100 mg/kg/day OD or BD
OPD	Yes - IM injection in OPD for mild-moderate infection
IPD	Yes - IV for serious infections
Duration	CAP: 5-7 days; Meningitis: 10-14 days; Typhoid: 10-14 days; Gonorrhea: single dose
Uses	CAP (atypical cover add azithromycin), meningitis, typhoid, gonorrhea, UTI, skin infections, septicemia
Contraindications	Cephalosporin allergy; neonates with jaundice (displaces bilirubin from albumin); not with calcium-containing IV fluids in neonates
CNS penetration	YES - can treat meningitis
Convenience	Once daily dosing - major advantage

CEFOTAXIME

Parameter	Detail
Form	Injection 500 mg, 1 g, 2 g
Dose	1-2 g IV every 8-12 hours
Uses	Same as ceftriaxone; preferred in neonatal meningitis

CEFTAZIDIME (Anti-Pseudomonal)

Parameter	Detail
Form	Injection 500 mg, 1 g, 2 g
Dose	1-2 g IV every 8 hours
OPD	NO
IPD	YES - ICU
Uses	Pseudomonas infections, hospital-acquired pneumonia, febrile neutropenia, cystic fibrosis lung infections

FOURTH GENERATION

CEFEPIME

Parameter	Detail
Form	Injection 500 mg, 1 g, 2 g
Dose	1-2 g IV every 8-12 hours
Uses	Febrile neutropenia, hospital infections, Pseudomonas, ESBL-producing organisms (with other agents)

FIFTH GENERATION

CEFTAROLINE

Parameter	Detail
Unique feature	ONLY beta-lactam active against MRSA
Dose	600 mg IV every 12 hours
Uses	MRSA skin infections, community-acquired pneumonia

1C. CARBAPENEMS

Heading: Cell Wall Synthesis Inhibitors > Beta-Lactam Antibiotics > Carbapenems MOA (one line): Broadest-spectrum beta-lactams - block PBP, resist most beta-lactamases - last resort antibiotics

IMIPENEM + CILASTATIN (Primaxin)

Parameter	Detail
Form	Injection: 250 mg, 500 mg vials
Dose	500 mg IV every 6 hours (QID) or 1 g every 8 hours
Why cilastatin?	Imipenem is broken down in kidneys by dehydropeptidase-1; cilastatin inhibits this enzyme, protecting imipenem
OPD	NO
IPD	YES - ICU only
Duration	7-14 days
Uses	Multi-drug resistant hospital infections, polymicrobial infections, ESBL/KPC-producing organisms, intra-abdominal sepsis, severe pneumonia
Contraindications	Carbapenem allergy; seizure history (imipenem is epileptogenic at high doses)
ADR	Seizures - most important

MEROPENEM

Parameter	Detail
Form	Injection 500 mg, 1 g
Dose	1-2 g IV every 8 hours
Advantage over Imipenem	More stable, less epileptogenic, better CNS penetration - PREFERRED for meningitis
Meningitis dose	2 g IV every 8 hours

ERTAPENEM

Parameter	Detail
Advantage	Once daily dosing (OD) - 1 g IV/IM OD
Limitation	NO Pseudomonas activity - important difference from meropenem/imipenem
Uses	Community-acquired infections, step-down therapy, ESBL infections

1D. MONOBACTAMS

AZTREONAM

Parameter	Detail
MOA	Beta-lactam but only active against gram-negative aerobic bacteria
Form	Injection 500 mg, 1 g, 2 g
Dose	1-2 g IV/IM every 6-12 hours
Key advantage	Safe in penicillin-allergic patients (no cross-reactivity)
Uses	Gram-negative infections in penicillin-allergic patients, Pseudomonas

2. CELL WALL - NON-BETA-LACTAMS

VANCOMYCIN ⭐⭐

Heading: Cell Wall Synthesis Inhibitors > Glycopeptide Antibiotics MOA (one line): Binds D-Ala-D-Ala terminus of peptidoglycan precursor - blocks transglycosylase - BACTERICIDAL (different step from penicillin)

Parameter	Detail
Form	Injection: 500 mg, 1 g vials; Oral capsules/solution 125 mg, 250 mg
IV dose	15-20 mg/kg IV every 8-12 hours (based on actual body weight)
Standard adult	1 g IV BD or 500 mg QID
Oral dose	125 mg QID (ONLY for C. difficile - oral vancomycin is NOT absorbed systemically)
Infusion time	MUST infuse over 60-90 minutes - slower the better
OPD	Oral only for C. diff (rare)
IPD	Yes - IV for systemic infections
Duration	MRSA bacteremia: 14-42 days; MRSA pneumonia: 7-14 days; C. diff: 10 days (oral)
Uses	MRSA (drug of choice), MSSA in penicillin allergy, Enterococcal infections, C. difficile colitis (oral form only)
Contraindications	Known allergy to vancomycin
ADR	Red Man Syndrome (rapid infusion), nephrotoxicity, ototoxicity
Monitoring	Trough levels (target 10-20 mcg/mL); renal function (SCr, CrCl)
Dose calculation example	70 kg patient: 70 × 15 = 1050 mg ≈ 1g BD

Red Man Syndrome: Flushing, erythema, hypotension from histamine release if infused fast. NOT an allergy. Treat by slowing infusion, antihistamines.

3. AMINOGLYCOSIDES

Heading: Protein Synthesis Inhibitors > 30S Ribosomal Inhibitors > Aminoglycosides MOA (one line): Bind IRREVERSIBLY to 30S ribosome - cause misreading of mRNA - make wrong proteins - ALSO disrupt cell membrane = BACTERICIDAL (unique among 30S drugs)

GENTAMICIN ⭐

Parameter	Detail
Form	Injection: 40 mg/mL, 80 mg/2 mL; Eye/Ear drops
Traditional dosing	1-1.7 mg/kg IV/IM every 8 hours (TDS)
Once-daily dosing (modern)	5-7 mg/kg IV OD (concentration-dependent killing - preferred)
Pediatric	2.5 mg/kg IV/IM every 8 hours
Neonates	4-7 mg/kg IV/IM every 24-48 hours
OPD	Rarely (topical eye/ear drops)
IPD	YES - IV for systemic infections
Duration	5-7 days maximum (toxicity risk increases beyond 7-10 days)
Uses	Gram-negative sepsis, pyelonephritis, hospital infections, Pseudomonas (combine with pip-tazo or ceftazidime), Enterococcal endocarditis (synergy with penicillin)
Contraindications	Pre-existing kidney disease, deafness, concurrent nephrotoxic drugs (avoid with vancomycin if possible)
ADR	Nephrotoxicity (reversible), ototoxicity - cochlear (irreversible hearing loss) and vestibular (balance), neuromuscular blockade
Monitoring	Peak level (30 min after infusion end); Trough (just before next dose); serum creatinine

Dose calculation - Traditional:

Patient 60 kg, normal renal function
Dose = 1.5 mg/kg = 1.5 × 60 = 90 mg ≈ 80 mg (available vial) IV/IM every 8 hours

Dose calculation - Once daily:

5 mg/kg × 60 kg = 300 mg IV once daily
Check trough level before second dose - must be < 1 mcg/mL

AMIKACIN

Parameter	Detail
Form	Injection: 100 mg/2 mL, 250 mg/mL, 500 mg/2 mL
Dose	15 mg/kg/day IV/IM OD or divided BD
Standard adult	500 mg-1 g IV BD or 15 mg/kg OD
OPD	NO
IPD	YES
Duration	7-10 days max
Uses	Resistant gram-negative infections (gentamicin-resistant organisms), hospital-acquired infections, MDR-TB (second-line)
Why reserved?	Has the broadest aminoglycoside activity - reserve for resistant cases

STREPTOMYCIN

Parameter	Detail
Form	Injection: 1 g/vial IM only (never IV)
TB dose	15 mg/kg IM OD (max 1 g/day)
Duration	2 months (intensive phase of TB regimen)
Uses	TB (2nd line after HRZE), Brucellosis (with doxycycline), Plague, Tularemia
ADR	Vestibular toxicity (balance > hearing), nephrotoxicity

TOBRAMYCIN

Parameter	Detail
Form	Injection; Inhaled solution (TOBI); Eye drops
IV dose	1.7 mg/kg IV every 8 hours or 5-7 mg/kg OD
Inhaled dose	300 mg inhaled BD (for cystic fibrosis - Pseudomonas)
Uses	Pseudomonas infections (better than gentamicin vs Pseudomonas), keratitis (eye drops), cystic fibrosis

NEOMYCIN

Parameter	Detail
Form	Topical cream/ointment; Oral tablets (NOT for systemic use)
Oral dose	1 g every 4 hours × 24 hours (pre-op bowel prep)
NOT used systemically	Too toxic for IV/IM
Uses	Topical skin infections (Neosporin cream = neomycin + polymyxin + bacitracin), pre-surgical bowel decontamination, hepatic encephalopathy (reduces ammonia-producing bacteria)

4. TETRACYCLINES

Heading: Protein Synthesis Inhibitors > 30S Ribosomal Inhibitors > Tetracyclines MOA (one line): Block attachment of aminoacyl-tRNA to the 30S ribosome-mRNA complex - protein synthesis pauses - BACTERIOSTATIC

DOXYCYCLINE ⭐ (Most important tetracycline)

Parameter	Detail
Form	Capsules/Tablets 100 mg; Injection 100 mg/vial
Loading dose	200 mg on Day 1 (as 100 mg BD)
Maintenance	100 mg OD or BD
OPD	YES - very commonly prescribed
IPD	Yes (IV for severe cases)
Duration	Acne: months (100 mg OD); Chlamydia: 7 days (100 mg BD); Lyme disease: 14-21 days; CAP: 5-7 days; Malaria prophylaxis: during travel + 4 weeks after
Uses	Rickettsia (Rocky Mountain spotted fever - drug of choice), Chlamydia (STIs, PID, psittacosis), Lyme disease (drug of choice), Acne vulgaris, Brucellosis (with streptomycin), Malaria prophylaxis, Cholera, Anthrax, MRSA skin infections, CAP (atypicals)
Contraindications	Children under 8 years, pregnancy, lactation
Food	Can take with food (reduces GI upset); AVOID dairy, antacids, iron (chelation - 2 hours gap)
ADR	Photosensitivity (tell patients to use sunscreen), GI upset, esophageal ulcers (take with water and remain upright), teeth staining in children

TETRACYCLINE (Plain)

Parameter	Detail
Form	Capsules 250 mg, 500 mg; Eye ointment; Topical
Dose	250-500 mg QID (every 6 hours)
Frequency	QID - awkward; doxycycline preferred
Take	Empty stomach (chelation with food)
Uses	Acne, H. pylori eradication regimens, rickettsial infections, anthrax
OPD	Yes

MINOCYCLINE

Parameter	Detail
Form	Capsules 50 mg, 100 mg
Dose	100 mg BD
Special property	Covers MRSA (skin infections); best tissue penetration of all tetracyclines
ADR	Vestibular side effects (dizziness, vertigo) - unique to minocycline
Uses	Acne (preferred), MRSA skin infections, meningococcal carrier state

5. MACROLIDES

Heading: Protein Synthesis Inhibitors > 50S Ribosomal Inhibitors > Macrolides MOA (one line): Bind 50S ribosome at 23S rRNA - block translocation step - peptide chain cannot move forward - BACTERIOSTATIC (bactericidal at high concentrations)

AZITHROMYCIN ⭐ (Z-Pack)

Parameter	Detail
Form	Tablets 250 mg, 500 mg; Syrup 200 mg/5 mL; Injection 500 mg/vial; Eye drops
Standard course	500 mg Day 1, then 250 mg OD for 4 days (Z-pack = 5 days total)
Simpler dosing	500 mg OD for 3-5 days (equally effective)
Single dose	1 g PO single dose for uncomplicated Chlamydia (urethritis/cervicitis)
Pediatric	10 mg/kg OD × 3 days
IV dose	500 mg IV OD
OPD	YES - very commonly prescribed
IPD	Yes (IV for hospitalized CAP)
Duration by disease	CAP: 5 days; Chlamydia: single dose (1g) or 5 days; Typhoid prophylaxis: not standard; MAC prophylaxis in AIDS: 1200 mg once weekly
Uses	CAP (combined with ceftriaxone), Chlamydia, Mycoplasma, Legionella, Pertussis, Atypical pneumonia, Traveller's diarrhea (Campylobacter), MAC in HIV
Contraindications	QTc prolongation history; liver disease (caution); known allergy
ADR	QTc prolongation (avoid with other QT-prolonging drugs), GI upset (mild - better than erythromycin), liver toxicity (rare)
Half-life	68 hours! - drug stays in tissues for days after last dose - hence short courses work

ERYTHROMYCIN

Parameter	Detail
Form	Tablets 250 mg, 500 mg; Syrup 125 mg/5 mL, 250 mg/5 mL; Injection; Topical/Eye ointment
Dose	250-500 mg QID (every 6 hours)
IV dose	500 mg-1 g IV every 6 hours
OPD	Yes - but poor GI tolerance limits use
Duration	7-10 days
Uses	Atypical pneumonia, Chlamydia (pregnancy - safe alternative to doxycycline), Pertussis (whooping cough - drug of choice), Campylobacter enteritis, Legionnaire's disease, motility disorders (at low doses - prokinetic)
ADR	Severe GI side effects (nausea, vomiting, cramps - stimulates motilin receptors), QTc prolongation, hepatotoxicity (cholestatic jaundice)
Drug interactions	Inhibits CYP3A4 - increases levels of warfarin, theophylline, cyclosporine

CLARITHROMYCIN

Parameter	Detail
Form	Tablets 250 mg, 500 mg; Syrup 125 mg/5 mL; XL (extended release) 500 mg
Dose	250-500 mg BD
OPD	YES
Duration	H. pylori: 7-14 days; CAP: 7-10 days; MAC: lifelong in AIDS
Uses	H. pylori eradication (triple therapy with amoxicillin + PPI), CAP, atypical infections, MAC in HIV/AIDS, Helicobacter, skin infections
ADR	Bitter/metallic taste, GI upset, QTc prolongation, CYP3A4 inhibitor

6. CHLORAMPHENICOL

Heading: Protein Synthesis Inhibitors > 50S Ribosomal Inhibitors > Chloramphenicol MOA (one line): Binds 50S ribosome - inhibits peptidyl transferase enzyme - stops peptide bond formation - BACTERIOSTATIC (bactericidal against H. influenzae, pneumococcus, meningococcus)

Parameter	Detail
Form	Capsules 250 mg, 500 mg; Injection 1 g/vial; Eye drops/ointment; Ear drops
Adult dose	250-500 mg QID or 50 mg/kg/day divided QID
IV dose	50 mg/kg/day divided every 6 hours
OPD	Rarely (eye/ear drops commonly)
IPD	Yes - for specific indications
Duration	Typhoid: 14 days; Meningitis: 10-14 days
Uses	Typhoid (less common now - fluoroquinolones preferred), Bacterial meningitis (if allergic to beta-lactams), Rickettsial infections (when doxycycline contraindicated - pregnancy), Brain abscess, Anaerobic infections
Contraindications	Neonates (Grey Baby Syndrome), history of blood dyscrasias, pregnancy near term
ADR	Aplastic anemia (rare, irreversible, idiosyncratic - 1:25,000-40,000), Bone marrow suppression (dose-related, reversible), Grey Baby Syndrome (neonates - lack glucuronyl transferase - drug accumulates - cardiovascular collapse, death)
Monitoring	CBC regularly; plasma levels if neonates

7. CLINDAMYCIN

Heading: Protein Synthesis Inhibitors > 50S Ribosomal Inhibitors > Lincosamides > Clindamycin MOA (one line): Binds 50S ribosome at same site as macrolides - blocks translocation step - BACTERIOSTATIC; excellent bone and abscess penetration

Parameter	Detail
Form	Capsules 150 mg, 300 mg; Injection 150 mg/mL; Topical gel/cream
Adult oral dose	150-300 mg every 6 hours (QID); severe: 300-450 mg QID
IV dose	600 mg-1.2 g IV every 6-8 hours
OPD	YES
IPD	Yes (IV)
Duration	Skin infections: 7-10 days; Bone infections: 4-6 weeks; Dental: 7 days; PID: 14 days
Uses	MSSA/MRSA skin and soft tissue infections (excellent), Bone and joint infections (osteomyelitis - penetrates bone well), Anaerobic infections (dental abscess, lung abscess, intra-abdominal), PID (with gentamicin), Toxoplasmosis (with pyrimethamine in AIDS), Acne (topical), Malaria (with quinine or primaquine)
Contraindications	History of C. difficile colitis, pseudomembranous colitis
ADR	Pseudomembranous colitis (C. difficile) - the CLASSIC cause; diarrhea, abdominal pain; if occurs - STOP immediately and treat with oral vancomycin or fidaxomicin

8. FLUOROQUINOLONES

Heading: DNA/RNA Synthesis Inhibitors > DNA Gyrase (Topoisomerase II) Inhibitors > Fluoroquinolones MOA (one line): Block bacterial DNA gyrase (Topoisomerase II) and Topoisomerase IV - DNA cannot uncoil for replication - strand breaks - cell dies = BACTERICIDAL; concentration-dependent killing

CIPROFLOXACIN ⭐

Parameter	Detail
Form	Tablets 250 mg, 500 mg, 750 mg; Injection 200 mg/100 mL, 400 mg/200 mL; Eye/Ear drops; Suspension
Oral dose	250-750 mg BD (every 12 hours)
IV dose	200-400 mg IV BD (infuse over 60 min)
OPD	YES - oral commonly used
IPD	Yes (IV)
Duration by disease:
- UTI (uncomplicated)	250 mg BD × 3 days
- Complicated UTI / Pyelonephritis	500 mg BD × 7-14 days
- Typhoid fever	500 mg BD × 7-14 days
- Respiratory infections	500-750 mg BD × 7-14 days
- Anthrax prophylaxis	500 mg BD × 60 days
- Gonorrhea	500 mg single oral dose (resistance increasing)
- Traveller's diarrhea	500 mg BD × 3 days
Uses	UTI, Typhoid, Pseudomonas infections, Anthrax (drug of choice), Gonorrhea, Respiratory tract infections, Traveller's diarrhea, Bone and joint infections
Contraindications	Children under 18 (cartilage damage - except anthrax/inhalation), pregnancy, lactation, QTc prolongation
ADR	Tendinopathy/tendon rupture (especially Achilles - stop immediately if tendon pain), CNS effects (headache, dizziness, rarely seizures), QTc prolongation, photosensitivity, GI upset
Drug interactions	Chelated by antacids/calcium/iron (2-hour gap); increases theophylline levels
NOTE	Best oral anti-Pseudomonal drug available

LEVOFLOXACIN ⭐ (Respiratory Quinolone)

Parameter	Detail
Form	Tablets 250 mg, 500 mg, 750 mg; Injection 500 mg/100 mL
Dose	500-750 mg OD (once daily - major advantage)
OPD	YES
IPD	YES (IV)
Duration	CAP: 5-7 days; Pyelonephritis: 5-7 days (750 mg OD); HAP: 7-14 days; TB (2nd line): months
Uses	CAP (especially when atypical cover needed), HAP, complicated UTI, pyelonephritis, skin infections, TB (2nd line - MDR-TB)
Advantage	Better pneumococcal coverage than ciprofloxacin - "respiratory quinolone"
Contraindications	Same as ciprofloxacin; tendon history

MOXIFLOXACIN

Parameter	Detail
Form	Tablets 400 mg; Injection 400 mg/250 mL; Eye drops
Dose	400 mg OD
Unique feature	Covers ANAEROBES (unlike other quinolones); best respiratory coverage
NOT for UTI	Excreted in bile - insufficient urinary concentrations
Uses	CAP (once daily - best compliance), intra-abdominal infections, MDR-TB
ADR	Greater QTc prolongation than other quinolones - monitor carefully

NORFLOXACIN / OFLOXACIN

Parameter	Detail
Norfloxacin	400 mg BD - mainly for UTI and GI infections (poor systemic distribution)
Ofloxacin	200-400 mg BD - UTI, respiratory infections, STIs

9. SULFONAMIDES + TRIMETHOPRIM

Heading: Folate Synthesis Inhibitors > Sulfonamides & Antifolates MOA (one line): Sulfonamides are PABA analogs blocking dihydropteroate synthase (Step 1 of folate synthesis); Trimethoprim blocks dihydrofolate reductase (Step 2) - together = sequential double blockade = synergistic BACTERICIDAL effect

CO-TRIMOXAZOLE / TMP-SMX ⭐ (Trimethoprim + Sulfamethoxazole)

Parameter	Detail
Form	Tablets: Single strength (80 mg TMP + 400 mg SMX), Double strength DS (160 mg TMP + 800 mg SMX); Syrup 40mg+200mg/5mL; Injection
Standard adult oral dose	1 DS tablet BD (every 12 hours)
OPD	YES
IPD	Yes (IV for severe PCP)
Duration by disease:
- UTI (uncomplicated)	1 DS tab BD × 3 days
- Complicated UTI	1 DS tab BD × 7-14 days
- PCP treatment	15-20 mg/kg/day TMP component IV divided every 6-8 hrs × 21 days
- PCP prophylaxis	1 SS tab OD or 1 DS tab 3x/week (lifelong in AIDS if CD4 < 200)
- Nocardiosis	1 DS tab BD × months
- MRSA skin infection	1-2 DS tabs BD × 7-14 days
Pediatric dose	8-10 mg/kg/day (TMP component) divided BD
Uses	UTI (most common use), PCP (Pneumocystis jirovecii pneumonia in HIV - drug of choice), Shigellosis, Nocardiosis, MRSA skin infections, Toxoplasmosis, Traveller's diarrhea
Contraindications	Sulfonamide allergy, G6PD deficiency, neonates under 2 months (kernicterus), pregnancy near term, severe renal/hepatic failure
ADR	Hypersensitivity rash, Stevens-Johnson syndrome, kernicterus (neonates), hemolytic anemia (G6PD deficiency), bone marrow suppression, crystalluria (drink plenty of water), nausea/vomiting

10. RIFAMPICIN (Rifampin)

Heading: DNA/RNA Synthesis Inhibitors > RNA Polymerase Inhibitors > Rifamycins MOA (one line): Inhibits bacterial DNA-dependent RNA polymerase (beta subunit) - RNA synthesis stops = BACTERICIDAL; must always use in combinations

Parameter	Detail
Form	Capsules 150 mg, 300 mg, 450 mg, 600 mg; Injection 300 mg, 600 mg/vial; Combined tablets (with INH)
TB dose	10 mg/kg/day OD (max 600 mg/day)
Standard adult	450 mg OD (< 50 kg) or 600 mg OD (> 50 kg)
OPD	YES - daily oral self-administration (TB-DOTS program)
IPD	Yes (IV for critical cases)
Duration	TB: 6 months total (2 months HRZE + 4 months HR); Leprosy: 6-12 months; Meningococcal prophylaxis: 2 days
Uses	TB (essential first-line - most potent sterilizing drug), Leprosy, Meningococcal prophylaxis (contacts), Brucellosis (combined), MRSA (always in combination - never alone)
Contraindications	Hepatic impairment (use with caution + monitor LFTs); jaundice
ADR	Orange-red discoloration of urine/tears/saliva/sweat (HARMLESS - warn patients), hepatotoxicity (monitor LFTs), GI upset, flu-like syndrome (intermittent dosing), thrombocytopenia
Critical interaction	POTENT CYP450 INDUCER - reduces levels of: OCP (use barrier contraception!), warfarin (increase dose), HIV drugs, corticosteroids, many others
Golden Rule	NEVER give rifampicin alone - resistance develops within 7-10 days

11. METRONIDAZOLE

Heading: DNA Synthesis Inhibitors > Nitroimidazoles > Metronidazole MOA (one line): Prodrug - activated by anaerobic ferredoxin to toxic free radicals - damages bacterial DNA - BACTERICIDAL against anaerobes and protozoa (selectively active in anaerobic/low-oxygen environments)

Parameter	Detail
Form	Tablets 200 mg, 400 mg; Injection 500 mg/100 mL; Oral suspension; Vaginal gel; Topical cream
Oral adult dose	400-500 mg TDS (every 8 hours)
IV dose	500 mg IV every 8 hours (TDS)
OPD	YES
IPD	Yes (IV)
Duration by disease:
- Giardiasis	400 mg TDS × 5-7 days
- Amoebiasis (invasive)	400-800 mg TDS × 5-10 days (then add diloxanide furoate 500 mg TDS × 10 days for luminal amoeba)
- Trichomoniasis	2 g single dose (treat both partners)
- Bacterial vaginosis	400 mg BD × 7 days OR 2 g single dose
- C. difficile colitis	500 mg TDS × 10-14 days (mild-moderate; vancomycin preferred for severe)
- Anaerobic infections	500 mg TDS × 7-10 days
- H. pylori	400 mg BD or TDS (part of triple therapy) × 7-14 days
- Dental infections (abscess)	200-400 mg TDS × 5-7 days
Uses	Giardiasis (drug of choice), Amoebiasis, Trichomoniasis (drug of choice), Bacterial vaginosis, C. difficile colitis, Anaerobic infections, H. pylori, Dental/surgical prophylaxis
Contraindications	1st trimester pregnancy (theoretical teratogenicity), neurological disease (high doses), history of metronidazole allergy
ADR	Metallic taste, nausea, GI upset, Disulfiram-like reaction with alcohol (severe flushing, headache, vomiting - MUST avoid alcohol during treatment and 48 hours after), peripheral neuropathy (prolonged use), CNS toxicity at high doses

12. ANTIMYCOBACTERIAL DRUGS - TUBERCULOSIS

Heading: Antimycobacterial Agents > Anti-Tuberculosis Drugs > First-Line Drugs Mnemonic: HRZE (Harry Runs Zinc Every day) = Isoniazid, Rifampicin, Pyrazinamide, Ethambutol

Standard TB Treatment Regimen:

Intensive phase: 2 months - HRZE (all 4 drugs)
Continuation phase: 4 months - HR (only Isoniazid + Rifampicin)
Total duration: 6 months (for drug-sensitive pulmonary TB)

ISONIAZID (INH) ⭐

MOA (one line): Prodrug activated by mycobacterial catalase-peroxidase (KatG) to reactive intermediates that block mycolic acid synthesis (unique to mycobacterial cell wall) - bactericidal against actively dividing TB

Parameter	Detail
Form	Tablets 100 mg, 300 mg; Injection 100 mg/mL; Syrup
Dose	5 mg/kg/day OD (max 300 mg/day)
Standard adult	300 mg OD (empty stomach - better absorption)
OPD	YES - daily self-administered (DOTS)
Duration	6 months (treatment); 6-9 months (latent TB prophylaxis - INH alone)
Uses	TB treatment (essential), Latent TB prophylaxis (9 months OD or 3 months INH+Rifampicin)
Contraindications	Active hepatic disease, previous INH hepatotoxicity, known allergy
ADR	Peripheral neuropathy (most common - due to B6/pyridoxine deficiency - give pyridoxine 10-25 mg OD with INH!), Hepatotoxicity (monitor LFTs - stop if > 3× normal with symptoms), Lupus-like syndrome, Pyridoxine deficiency
Always co-prescribe	Pyridoxine 10-25 mg OD to prevent peripheral neuropathy

PYRAZINAMIDE (PZA/Z)

MOA (one line): Active only at acidic pH (inside macrophages) - kills dormant intracellular TB - unique "sterilizing" activity where no other drug works

Parameter	Detail
Form	Tablets 500 mg
Dose	25 mg/kg/day OD (max 2 g/day)
Standard adult	1000-1500 mg OD
OPD	YES
Duration	Only 2 months (intensive phase) - not continued further
ADR	Hepatotoxicity (must monitor LFTs), Hyperuricemia/Gout (blocks uric acid excretion), arthralgia, GI upset

ETHAMBUTOL (E)

MOA (one line): Inhibits arabinosyl transferase - blocks arabinogalactan synthesis in mycobacterial cell wall - bacteriostatic (prevents resistance to other drugs)

Parameter	Detail
Form	Tablets 200 mg, 400 mg, 600 mg, 800 mg
Dose	15-25 mg/kg/day OD
Standard adult	800-1200 mg OD
OPD	YES
Duration	2 months (intensive phase); continue only if resistance suspected
ADR	Optic neuritis (most important - dose-related, usually reversible - causes blurred vision, loss of red-green color discrimination) - test color vision and visual acuity before and during treatment; avoid if cannot monitor vision (young children)

13. ANTI-LEPROSY DRUGS

Heading: Antimycobacterial Agents > Anti-Leprosy Drugs > Multi-Drug Therapy (MDT)

WHO Multi-Drug Therapy (MDT) - Standard Regimens:

DAPSONE

MOA (one line): Like sulfonamides - inhibits dihydropteroate synthase in M. leprae - bacteriostatic against M. leprae

Parameter	Detail
Form	Tablets 50 mg, 100 mg
Dose	100 mg OD
Regimen:	Paucibacillary leprosy (PB): 6 months; Multibacillary leprosy (MB): 12 months
ADR	Hemolytic anemia (especially G6PD deficiency), methemoglobinemia, agranulocytosis, "Dapsone Syndrome" (fever, rash, hepatitis)

CLOFAZIMINE

MOA (one line): Binds mycobacterial DNA - interferes with DNA replication - also has anti-inflammatory activity

Parameter	Detail
Form	Capsules 50 mg, 100 mg
Dose	50 mg OD (maintenance) + 300 mg once monthly (supervised)
ADR	Skin discoloration (red-brown-black pigmentation - cosmetically distressing, reversible after stopping), GI symptoms, ichthyosis

MDT SUMMARY TABLE

Type	Drugs	Duration
Paucibacillary (PB) - 1-5 skin lesions	Rifampicin 600 mg once monthly (supervised) + Dapsone 100 mg OD (self-administered)	6 months
Multibacillary (MB) - > 5 lesions	Rifampicin 600 mg once monthly + Clofazimine 300 mg once monthly (supervised) + Dapsone 100 mg OD + Clofazimine 50 mg OD (self-administered)	12 months

SECTION B: ANTIFUNGALS

Heading: Antifungal Agents

The fungi-human difference (basis of selective toxicity): Fungi have ergosterol in their cell membrane (humans have cholesterol). Antifungals target ergosterol or its synthesis.

1. POLYENES - Amphotericin B

Heading: Antifungal Agents > Systemic Antifungals > Polyene Antifungals MOA (one line): Binds directly to ergosterol in fungal cell membrane - forms pores - cell contents leak out - FUNGICIDAL

AMPHOTERICIN B (AmB) ⭐

Parameter	Detail
Form	Injection: 50 mg/vial (deoxycholate formulation); Lipid formulations: AmBisome (liposomal - preferred, less toxic)
Dose - Conventional	0.3-1.5 mg/kg/day IV OD
Starting dose	0.1 mg/kg test dose first (to check for infusion reactions), then escalate to full dose
Dose - Liposomal (AmBisome)	3-5 mg/kg/day IV OD (less nephrotoxic)
OPD	NO
IPD	YES - ICU/Specialist ward only
Infusion	Slow IV infusion over 2-6 hours (darkness - light sensitive); premedicate with paracetamol + antihistamine + hydrocortisone to reduce infusion reactions
Duration	Candida: 2-4 weeks; Cryptococcal meningitis: 2 weeks induction, then fluconazole maintenance; Aspergillus: 4-12 weeks
Uses	Severe systemic fungal infections (Aspergillosis, Cryptococcal meningitis, Histoplasmosis, Candida bloodstream infections/endocarditis, Mucormycosis - drug of CHOICE), Visceral leishmaniasis (AmBisome)
Contraindications	Severe renal impairment (use liposomal form), hypokalemia
ADR	Nephrotoxicity (major dose-limiting toxicity - monitor creatinine, BUN, electrolytes), Infusion reactions (fever, rigors, chills, headache, hypotension - "amphotericin shakes"), Hypokalemia and hypomagnesemia (replenish), Anemia (reduces erythropoietin)
Monitoring	Daily renal function, electrolytes; CBC weekly

NYSTATIN

Parameter	Detail
Form	Oral drops 100,000 units/mL; Tablets; Vaginal tablets 100,000 units; Cream/ointment/powder
Dose - Oral candidiasis	100,000-500,000 units (1-5 mL) QID - swish and swallow
Vaginal dose	1-2 vaginal tabs intravaginally BD for 7-14 days
NOT systemically absorbed	Only topical/mucocutaneous use
OPD	YES - oral drops very common
Uses	Oral thrush (neonates and adults), Esophageal candidiasis (when fluconazole unavailable), Vaginal candidiasis, Diaper rash (topical)
Contraindications	None significant (not absorbed)
ADR	GI upset (nausea/vomiting), bitter taste

2. AZOLE ANTIFUNGALS

Heading: Antifungal Agents > Azole Antifungals MOA (one line): Inhibit fungal CYP450 enzyme 14-alpha-demethylase - block lanosterol → ergosterol conversion - ergosterol depleted - membrane function disrupted - FUNGISTATIC (fungicidal at high concentrations)

FLUCONAZOLE ⭐

Parameter	Detail
Form	Tablets/Capsules 50 mg, 100 mg, 150 mg, 200 mg; Injection 200 mg/100 mL; Syrup 50 mg/5 mL
Vaginal candidiasis	150 mg single oral dose (single tablet!)
Oral/esophageal candidiasis	100-200 mg OD × 7-14 days
Systemic candidiasis	400-800 mg IV/PO OD
Cryptococcal meningitis (maintenance)	200-400 mg OD (lifelong in AIDS - secondary prophylaxis after AmB induction)
Prophylaxis in immunocompromised	50-100 mg OD
OPD	YES - very common (especially 150 mg single dose)
IPD	YES (IV)
Duration	Vaginal: single dose or 3 days; Oral thrush: 7-14 days; Systemic: weeks-months
Uses	Candidiasis (all forms - vaginal, oral, esophageal, systemic), Cryptococcal meningitis (maintenance), Prophylaxis in transplant/immunocompromised patients, Tinea infections (some)
Contraindications	Concurrent QTc-prolonging drugs; liver disease; pregnancy (teratogenic in 1st trimester)
ADR	GI upset, elevated LFTs, headache, rash, QTc prolongation
Drug interactions	Inhibits CYP3A4 and CYP2C9 - increases levels of warfarin, statins, sulfonylureas

ITRACONAZOLE

Parameter	Detail
Form	Capsules 100 mg; Oral solution 10 mg/mL; Injection
Dose	100-200 mg OD or BD
Unique strength	Only azole active against Aspergillus (among older azoles)
OPD	YES
Duration	Onychomycosis (nail): "pulse therapy" - 200 mg BD × 1 week per month × 3 months (or 200 mg OD × 3 months continuously)
Uses	Aspergillosis, Histoplasmosis, Blastomycosis, Onychomycosis (nail fungus), Tinea versicolor, Candidiasis
Absorption	Capsule - take with food (better absorption); Solution - take on empty stomach
ADR	Hepatotoxicity, GI upset, negative inotropy (avoid in heart failure), edema

VORICONAZOLE ⭐

Parameter	Detail
Form	Tablets 50 mg, 200 mg; Injection 200 mg/vial; Oral suspension
Loading dose	6 mg/kg IV BD × 2 doses on Day 1
Maintenance	4 mg/kg IV BD (IPD) OR 200 mg PO BD (OPD)
Oral maintenance	200 mg BD (> 40 kg) or 100 mg BD (< 40 kg)
OPD	YES (oral)
IPD	YES (IV)
Duration	Invasive aspergillosis: minimum 6-12 weeks
Uses	DRUG OF CHOICE for Invasive Aspergillosis, Candida (resistant species), rare mold infections, Fusariosis
ADR	Visual disturbances (transient blurred vision, photopsia - very common, usually mild), hepatotoxicity, photosensitivity (prolonged use), skin cancers (long-term), hallucinations
Drug interactions	Strong CYP inhibitor; monitor carefully with other drugs

KETOCONAZOLE

Parameter	Detail
Form	Tablets 200 mg; Shampoo 2%; Cream 2%
Dose	200-400 mg OD
Now mainly topical	Systemic use has been RESTRICTED (hepatotoxicity risk) - shampoo for dandruff/tinea versicolor very common
Uses	Dandruff, Tinea versicolor (shampoo/cream), historically for systemic fungal infections
ADR	Hepatotoxicity (severe - restriction of systemic use), gynecomastia, adrenal insufficiency (inhibits steroid synthesis)

3. ECHINOCANDINS

Heading: Antifungal Agents > Echinocandin Antifungals MOA (one line): Inhibit beta-1,3-glucan synthase - block fungal cell wall glucan synthesis (no human equivalent) - FUNGICIDAL for Candida

CASPOFUNGIN

Parameter	Detail
Form	Injection: 50 mg, 70 mg/vial
Loading dose	70 mg IV OD on Day 1
Maintenance	50 mg IV OD
OPD	NO - IV only
IPD	YES
Duration	Candida: 14 days after last positive culture; Aspergillus: weeks
Uses	Invasive candidiasis/candidemia (drug of choice in ICU), salvage therapy for Aspergillosis (if AmB/voriconazole fail), empiric therapy in febrile neutropenia
Advantage	Works against Candida species resistant to azoles; safe in renal failure
ADR	Well-tolerated; infusion reactions, elevated LFTs, hypokalemia

4. OTHER ANTIFUNGALS

GRISEOFULVIN

Heading: Antifungal Agents > Other Antifungals > Griseofulvin MOA (one line): Accumulates in keratin of skin/nails/hair - inhibits fungal microtubule assembly - blocks mitosis - FUNGISTATIC

Parameter	Detail
Form	Tablets 125 mg, 250 mg, 500 mg; Suspension
Dose	500 mg-1 g OD (with fatty meal - best absorption)
OPD	YES
Duration	Tinea capitis (scalp): 4-6 weeks; Tinea corporis: 2-4 weeks; Tinea unguium (nails): fingernails 3-6 months, toenails 6-12 months
Uses	ONLY for dermatophytes (ringworm infections): Tinea capitis, Tinea corporis, Tinea pedis (athlete's foot), Onychomycosis
Not active against	Candida, Aspergillus
Contraindications	Pregnancy (teratogenic), porphyria, liver disease
ADR	Headache, GI upset, photosensitivity, hepatotoxicity, disulfiram-like reaction with alcohol

TERBINAFINE

MOA (one line): Inhibits fungal squalene epoxidase - blocks ergosterol synthesis at earlier step than azoles - FUNGICIDAL (unlike griseofulvin)

Parameter	Detail
Form	Tablets 250 mg; Cream 1%; Gel
Oral dose	250 mg OD
Duration	Tinea pedis: 2-6 weeks; Tinea corporis: 4 weeks; Onychomycosis (nails): fingernails 6 weeks, toenails 12 weeks
OPD	YES
Uses	Onychomycosis (most effective oral agent for nail fungus - first choice), Dermatophytoses, Tinea versicolor (topical)
ADR	GI upset, taste disturbance (ageusia - most troublesome), hepatotoxicity (rare), rash

SECTION C: ANTIVIRALS

Heading: Antiviral Agents Principle: Viruses use host cell machinery - antiviral drugs must target virus-specific steps: attachment/entry, nucleic acid synthesis (viral polymerases), assembly, or release

1. ANTI-HERPES DRUGS

Heading: Antivirals > Anti-Herpesvirus Agents > Nucleoside Analogs MOA (one line): Acyclovir (a guanosine analog) is phosphorylated by viral thymidine kinase (not human TK - selective) - becomes acyclovir triphosphate - inhibits viral DNA polymerase - terminates DNA chain - VIROSTATIC

ACYCLOVIR ⭐

Parameter	Detail
Form	Tablets 200 mg, 400 mg, 800 mg; IV powder for injection 250 mg/vial; Cream 5%; Eye ointment
Oral dose (Herpes labialis/HSV-1)	200-400 mg 5 times/day (every 4-5 hours) × 5-10 days
Genital herpes (primary)	400 mg TDS × 7-10 days
Suppressive therapy	400 mg BD (daily - prevents recurrences)
Varicella-zoster (Chickenpox - immunocompetent)	800 mg 5×/day × 5-7 days (start within 24 hours of rash)
Herpes Zoster (Shingles)	800 mg 5×/day × 7 days
IV dose - Herpes Encephalitis	10 mg/kg IV TDS (every 8 hours) × 14-21 days
IV dose - Neonatal herpes	20 mg/kg IV TDS × 21 days
OPD	YES (oral)
IPD	YES (IV for encephalitis, severe cases, immunocompromised)
Uses	HSV-1 and HSV-2 (oral and genital herpes), Varicella-zoster (chickenpox and shingles), Herpes encephalitis (IV - emergency), Herpes keratitis (topical), Neonatal herpes (IV)
Contraindications	Renal impairment (dose reduce), dehydration
ADR	GI upset (oral), Nephrotoxicity (IV - crystallizes in renal tubules - hydrate well, infuse slowly), Neurotoxicity (tremors, confusion - rare)
IV administration	Give over 1 hour with 500 mL fluid (prevents crystalluria)

VALACYCLOVIR (Prodrug of Acyclovir)

Parameter	Detail
Form	Tablets 500 mg, 1000 mg
Advantage	Better oral bioavailability (55% vs 10-20% for acyclovir) - FEWER tablets needed
Dose - Genital herpes (primary)	1 g BD × 10 days
Herpes Zoster	1 g TDS × 7 days
Suppressive therapy	500 mg OD
OPD	YES - preferred over acyclovir for convenience
Uses	Same as acyclovir - HSV-1, HSV-2, VZV

GANCICLOVIR

MOA (one line): Similar to acyclovir but activated by CMV kinase (UL97) - inhibits CMV DNA polymerase - active against CMV (cytomegalovirus)

Parameter	Detail
Form	Injection 500 mg/vial; Oral (Valganciclovir - prodrug)
IV induction	5 mg/kg IV BD × 14-21 days
IV maintenance	5 mg/kg IV OD × 7 days/week
Valganciclovir (oral)	900 mg BD (induction) or 900 mg OD (maintenance)
OPD	Valganciclovir tablets (OPD)
IPD	IV ganciclovir
Uses	CMV retinitis in AIDS (induction then maintenance), CMV prevention after organ transplant
ADR	Bone marrow suppression (neutropenia, thrombocytopenia - most important), nephrotoxicity, teratogenic

2. ANTI-INFLUENZA DRUGS

Heading: Antivirals > Anti-Influenza Agents > Neuraminidase Inhibitors MOA (one line): Oseltamivir/Zanamivir inhibit influenza neuraminidase enzyme - blocks release of new virus particles from infected cells - virus spreads poorly = VIROSTATIC

OSELTAMIVIR (Tamiflu) ⭐

Parameter	Detail
Form	Capsules 30 mg, 45 mg, 75 mg; Oral suspension 12 mg/mL
Treatment dose	75 mg BD × 5 days
Prophylaxis	75 mg OD × 7-10 days (post-exposure) or for season
Pediatric dose	Weight-based: < 15 kg: 30 mg BD; 15-23 kg: 45 mg BD; 24-40 kg: 60 mg BD; > 40 kg: 75 mg BD
OPD	YES
Start within	48 hours of symptom onset (most effective if early)
IPD	YES for severe/complicated influenza (hospitalized patients, ICU)
Duration	5 days treatment; 7-10 days post-exposure prophylaxis; up to 6 weeks seasonal prophylaxis
Uses	Influenza A and B treatment, Post-exposure prophylaxis, Seasonal prophylaxis (high-risk)
Contraindications	Severe renal failure (dose adjustment)
ADR	Nausea, vomiting (take with food), headache, rare neuropsychiatric events (especially in children - monitor)

ZANAMIVIR (Relenza)

Parameter	Detail
Form	Inhalation powder (Diskhaler)
Dose	2 inhalations (10 mg) BD × 5 days
NOT oral	Inhaled route only
Contraindications	Asthma/COPD (bronchospasm risk)
Uses	Influenza A and B, useful when oseltamivir resistance suspected

3. ANTIRETROVIRALS (HIV)

Heading: Antivirals > Anti-HIV Agents (Antiretrovirals = ARVs/ARTs) Principle: WHO recommends Highly Active Antiretroviral Therapy (HAART) = combination of 3 drugs from at least 2 different classes

HIV Life Cycle + Drug Targets

HIV entry → 1. Fusion/Entry Inhibitors (Enfuvirtide, Maraviroc)
           ↓
Reverse Transcriptase (RNA→DNA) → 2. NRTIs, NNRTIs
           ↓
Integration into host DNA → 3. Integrase Inhibitors (Raltegravir, Dolutegravir)
           ↓
Protein processing → 4. Protease Inhibitors (Ritonavir, Lopinavir)
           ↓
Assembly/Budding

CLASS A: NRTIs (Nucleoside Reverse Transcriptase Inhibitors)

MOA (one line): Incorporated into viral DNA by reverse transcriptase - act as fake nucleotides - terminate DNA chain elongation (chain terminators)

Drug	Brand	Dose	Special Notes
Tenofovir (TDF)	Viread	300 mg OD	Also active against HBV; Backbone of most regimens
Emtricitabine (FTC)	Emtriva	200 mg OD	Usually combined with TDF (= Truvada: TDF+FTC)
Lamivudine (3TC)	Epivir	150 mg BD or 300 mg OD	Also used for HBV; very well tolerated
Zidovudine (AZT)	Retrovir	300 mg BD	First anti-HIV drug; ADR: anemia, neutropenia
Abacavir (ABC)	Ziagen	300 mg BD or 600 mg OD	Test for HLA-B*5701 before starting (fatal hypersensitivity)

CLASS B: NNRTIs (Non-Nucleoside Reverse Transcriptase Inhibitors)

MOA (one line): Bind directly to reverse transcriptase at a non-active site - cause conformational change - enzyme cannot work (allosteric inhibition)

Drug	Brand	Dose	Special Notes
Efavirenz (EFV)	Sustiva	600 mg OD at night	CNS side effects (vivid dreams, dizziness); avoid in 1st trimester
Nevirapine (NVP)	Viramune	200 mg OD × 14 days then 200 mg BD	Rash, hepatotoxicity; widely used in pregnancy/PMTCT
Rilpivirine (RPV)	Edurant	25 mg OD with meal	Must take with food; lower pill burden
Doravirine (DOR)	Pifeltro	100 mg OD	Less CNS effects than efavirenz

CLASS C: Protease Inhibitors (PIs)

MOA (one line): Block HIV protease enzyme - immature non-infectious viral particles are made - virus cannot mature

Drug	Brand	Dose	Special Notes
Ritonavir (RTV)	Norvir	100-200 mg OD	Used mainly as "booster" (pharmacokinetic enhancer) - inhibits CYP3A4, boosting other PI levels
Lopinavir/Ritonavir (LPV/r)	Kaletra	400/100 mg BD	Common PI; many drug interactions
Atazanavir (ATV/r)	Reyataz	300 mg OD (+RTV 100 mg)	Causes benign hyperbilirubinemia (jaundice)
Darunavir (DRV/r)	Prezista	800/100 mg OD	Preferred PI; fewer side effects

CLASS D: Integrase Strand Transfer Inhibitors (INSTIs)

MOA (one line): Block HIV integrase enzyme - viral DNA cannot be inserted into host chromosome - virus cannot replicate persistently

Drug	Brand	Dose	Special Notes
Raltegravir (RAL)	Isentress	400 mg BD	First integrase inhibitor; well tolerated
Dolutegravir (DTG)	Tivicay	50 mg OD	High barrier to resistance; now PREFERRED globally - in WHO 1st line regimen (TDF+3TC+DTG)
Bictegravir (BIC)	Single-tab (Biktarvy)	Once daily	Coformulated with TAF+FTC

WHO FIRST-LINE ART REGIMEN (Current Standard):

TDF (Tenofovir) + 3TC (Lamivudine) + DTG (Dolutegravir) - All in 1 tablet, OD

4. ANTI-HEPATITIS DRUGS

SOFOSBUVIR (for Hepatitis C): MOA: Nucleotide analog NS5B polymerase inhibitor - blocks HCV RNA replication

Parameter	Detail
Form	Tablets 400 mg; Combined: Sofosbuvir/Ledipasvir (Harvoni), Sofosbuvir/Velpatasvir (Epclusa)
Dose	400 mg OD (combined with other DAAs)
Duration	8-12 weeks (depending on genotype and combination)
OPD	YES
Uses	Chronic Hepatitis C (pan-genotypic activity with combination DAA therapy)

ENTECAVIR / TENOFOVIR (for Hepatitis B):

Entecavir 0.5 mg OD (HBV naive) or 1 mg OD (treatment experienced)
Tenofovir 300 mg OD
Both: oral, OPD, lifelong (or until HBsAg seroconversion)
MOA: Inhibit HBV DNA polymerase (reverse transcriptase)

SECTION D: ANTIPROTOZOALS

1. ANTIMALARIALS

Heading: Antiprotozoal Agents > Antimalarial Drugs

CHLOROQUINE ⭐

MOA (one line): Concentrates in parasite food vacuole - prevents heme polymerization - toxic heme accumulates and kills the parasite - BLOOD SCHIZONTICIDE (kills erythrocytic stage)

Parameter	Detail
Form	Tablets 150 mg base (250 mg salt), 300 mg base (500 mg salt); Injection 40 mg base/mL
Treatment dose (P. vivax/P. malariae/P. ovale/sensitive P. falciparum)	10 mg base/kg OD × 2 days, then 5 mg base/kg on Day 3
Simpler standard	600 mg base (Day 1) + 300 mg base (Day 2) + 300 mg base (Day 3)
Prophylaxis	5 mg/kg/week (adults 300 mg base once weekly) - start 1-2 weeks before travel, continue 4 weeks after
OPD	YES
IPD	Severe malaria - IV
IV dose	10 mg base/kg slow IV infusion over 8 hours
Duration	3-day treatment course
Uses	P. vivax, P. ovale, P. malariae (drug of choice), Chloroquine-sensitive P. falciparum, Malaria prophylaxis (where sensitive), Autoimmune diseases (RA, SLE)
Contraindications	G6PD deficiency (relative), Retinal/visual field defects, Known chloroquine resistance
ADR	GI upset (take after meals), pruritus (especially in dark-skinned - Africans), headache, Visual disturbances; Long-term: Retinopathy (screen annually), Cardiomyopathy

PRIMAQUINE

MOA (one line): Active against liver hypnozoites (dormant forms) and gametocytes - prevents relapse of P. vivax and P. ovale (radical cure) - exact mechanism not fully known; may form reactive oxygen species

Parameter	Detail
Form	Tablets 7.5 mg, 15 mg
Dose	15 mg base OD × 14 days (for P. vivax/P. ovale radical cure)
Or	30 mg base OD × 7 days (alternative)
Gametocyte clearance	0.25 mg/kg single dose (for P. falciparum - prevents transmission)
OPD	YES
Duration	14 days for radical cure
Uses	Radical cure of P. vivax and P. ovale (MUST give after chloroquine to kill liver hypnozoites and prevent relapse), Gametocyte clearance in P. falciparum
ALWAYS check G6PD before prescribing	Primaquine causes severe HEMOLYTIC ANEMIA in G6PD-deficient patients (can be fatal)
Contraindications	G6PD deficiency, pregnancy (fetal G6PD not known), infants under 6 months
ADR	GI upset, Hemolytic anemia (G6PD deficiency), Methemoglobinemia

ARTEMISININ DERIVATIVES (ACT - Artemisinin-based Combination Therapy)

MOA (one line): Activated by heme iron inside parasite - generates toxic free radicals that kill the parasite - fastest-acting antimalarial - kills all stages including early ring forms

WHO RECOMMENDED ACTs for Uncomplicated P. falciparum:

Combination	Dose	Duration
Artemether-Lumefantrine (Coartem)	4 tabs (80+480 mg) BD × 3 days (with food/milk for absorption)	3 days (6 doses)
Artesunate-Amodiaquine	Fixed dose combination OD × 3 days	3 days
Artesunate-Mefloquine	Day 1-3 per protocol	3 days
DHA-Piperaquine	Once daily × 3 days	3 days

Severe/Complicated P. falciparum Malaria:

IV Artesunate - 2.4 mg/kg IV at 0, 12, 24 hours, then OD until oral is tolerated (minimum 24 hours IV before switching to oral ACT)
SUPERIOR to IV quinine (lower mortality) - Drug of Choice for severe malaria

QUININE

Parameter	Detail
Form	Tablets 200 mg, 300 mg; Injection (dihydrochloride) 300 mg/mL
IV dose for severe malaria	20 mg/kg loading dose IV over 4 hours, then 10 mg/kg IV every 8 hours
Oral dose	600 mg (salt) TDS × 7 days (plus doxycycline 100 mg BD × 7 days)
OPD	Oral for uncomplicated (now replaced by ACTs)
IPD	IV for severe malaria (if IV artesunate unavailable)
ADR	Cinchonism (tinnitus, headache, nausea, visual disturbances, dizziness), Hypoglycemia (stimulates insulin), QTc prolongation, Hemolytic anemia (G6PD), Blackwater fever (massive hemolysis)

2. ANTIAMOEBIC DRUGS

Heading: Antiprotozoal Agents > Antiamoebic Drugs

Drug	Type	MOA	Dose	Uses
Metronidazole	Tissue + luminal amoebicide	DNA damage (free radicals in anaerobic environment)	400-800 mg TDS × 5-10 days	Invasive amoebiasis (amoebic dysentery, amoebic liver abscess) - FIRST
Tinidazole	Tissue + luminal	Same as metronidazole	2 g OD × 3 days (simpler)	Same as metronidazole; better tolerated, shorter course
Diloxanide Furoate	Luminal amoebicide ONLY	Kills amoeba in intestinal lumen	500 mg TDS × 10 days	Asymptomatic cyst passers; always add AFTER metronidazole for intestinal amoeba
Emetine/Dehydroemetine	Tissue amoebicide	Inhibits protein synthesis	1 mg/kg/day IM × 3-5 days	Amoebic liver abscess (if metronidazole fails)

Standard Regimen for Amoebic Liver Abscess (OPD):

Metronidazole 400-800 mg TDS × 10 days
Then Diloxanide furoate 500 mg TDS × 10 days (to clear luminal cysts)

SECTION E: ANTIHELMINTHICS

Heading: Antihelminthic Drugs

1. BENZIMIDAZOLES

Heading: Antihelminthic Drugs > Benzimidazole Anthelmintics MOA (one line): Bind to beta-tubulin in helminths - block microtubule polymerization - worm's cell division stops, glucose absorption fails - worm dies slowly

ALBENDAZOLE ⭐ (Broadest spectrum antihelminthic)

Parameter	Detail
Form	Tablets 200 mg, 400 mg; Syrup 200 mg/5 mL
Single dose for intestinal worms	400 mg PO single dose
Tissue infections	400 mg BD × 3 days to several months
OPD	YES - can be dispensed without examination for many intestinal worm infections
Duration by disease:
- Ascariasis, Hookworm, Enterobius	400 mg single dose
- Trichuriasis (Whipworm)	400 mg OD × 3 days
- Strongyloides	400 mg OD × 3 days
- Giardia	400 mg OD × 5 days
- Neurocysticercosis	400 mg BD × 8-30 days (always with steroids + antiepileptics)
- Hydatid cyst (Echinococcus)	400 mg BD × 28 days, repeat 3 cycles with 14-day breaks (with or before surgery)
- Lymphatic filariasis (MDA)	Single dose 400 mg (combined with DEC 6 mg/kg or Ivermectin 200 mcg/kg) once yearly
Pediatric	Same 400 mg single dose (> 2 years); 200 mg (1-2 years)
Take with	Fatty meal (increases absorption by 5x)
Contraindications	Pregnancy (teratogenic - confirm not pregnant), liver disease
ADR	Usually minimal with single dose; with prolonged use: GI upset, elevated LFTs, bone marrow suppression

MEBENDAZOLE

Parameter	Detail
Form	Tablets 100 mg, 500 mg; Syrup
Dose	100 mg BD × 3 days (for most worms) or 500 mg single dose
OPD	YES
Uses	Ascariasis, Hookworm, Trichuriasis, Pinworm (Enterobius), Trichinosis (with steroids)
Contraindications	Pregnancy, under 2 years
NOT absorbed systemically - acts locally in intestines

2. IVERMECTIN ⭐

Heading: Antihelminthic Drugs > Macrocyclic Lactone Anthelmintics MOA (one line): Binds glutamate-gated chloride channels in nematode/arthropod nerve and muscle cells - causes hyperpolarization - irreversible paralysis - worm dies (selective - these channels not in humans)

Parameter	Detail
Form	Tablets 3 mg, 6 mg; Topical lotion
Dose	200 mcg/kg (0.2 mg/kg) PO single dose
Standard adult (70 kg)	70 × 0.2 = 14 mg ≈ 12 mg (2 × 6 mg tablets) single dose
OPD	YES
Duration by disease:
- Strongyloides stercoralis	200 mcg/kg OD × 2 days (or single dose, repeat in 2 weeks)
- Onchocerciasis (River blindness)	150 mcg/kg single dose yearly (mass drug administration)
- Lymphatic filariasis	200 mcg/kg + Albendazole 400 mg once yearly
- Scabies	200 mcg/kg single dose (repeat in 2 weeks); topical 1% cream
- Head lice (pediculosis)	200 mcg/kg single dose (or topical)
Take on	Empty stomach with water
Contraindications	Children under 15 kg, pregnancy, CNS disorders (blood-brain barrier disruption)
ADR	Usually mild; Mazzotti reaction (fever, rash, pruritus from dying parasites in onchocerciasis - give antihistamines), CNS toxicity (rare)

3. PRAZIQUANTEL ⭐

Heading: Antihelminthic Drugs > Praziquantel (Isoquinoline) MOA (one line): Increases permeability of worm cell membrane to calcium - massive calcium influx - tetanic paralysis - worm detaches from vessel/tissue and dies (or is expelled)

Parameter	Detail
Form	Tablets 150 mg, 600 mg
Dose	40-75 mg/kg/day divided into 2-3 doses on 1-2 days
Schistosomiasis	40 mg/kg single dose (S. haematobium, S. mansoni) or 20 mg/kg TDS × 1 day (S. japonicum)
Tapeworms (Taenia)	5-10 mg/kg single dose
Neurocysticercosis	50 mg/kg/day TDS × 15 days (with albendazole + corticosteroids + antiepileptics)
Liver flukes (Clonorchis, Opisthorchis)	75 mg/kg/day TDS × 2 days
OPD	YES
Uses	Drug of choice for ALL trematodes (flukes) and ALL tapeworms (cestodes), Schistosomiasis (drug of choice)
Contraindications	Ocular cysticercosis (worm in eye - killing it causes inflammation and blindness), concurrent rifampicin (reduces praziquantel levels)
ADR	Abdominal pain, nausea, dizziness, headache (usually mild); fever/urticaria from dying parasites

4. PYRANTEL PAMOATE

Heading: Antihelminthic > Tetrahydropyrimidine MOA (one line): Depolarizing neuromuscular blocking agent - causes spastic paralysis of worm - worm expelled by peristalsis (opposite of mebendazole which causes flaccid paralysis)

Parameter	Detail
Form	Suspension 50 mg/mL; Tablets 250 mg
Dose	10-11 mg/kg single dose (max 1 g)
OPD	YES - OTC in many countries
Uses	Ascariasis, Enterobiasis (pinworm), Hookworm
NOT effective	Trichuris, Strongyloides
Contraindications	Liver disease
ADR	Mild GI effects

5. DIETHYLCARBAMAZINE (DEC)

Heading: Antihelminthic > Anti-Filarial Drugs MOA (one line): Immobilizes microfilariae - alters surface membrane making them susceptible to host immune destruction; also kills adult worms by unknown mechanism

Parameter	Detail
Form	Tablets 50 mg, 100 mg
Dose	6 mg/kg/day divided TDS × 12 days
Lymphatic filariasis (MDA)	6 mg/kg single dose once yearly (combined with albendazole 400 mg)
OPD	YES
Duration	Lymphatic filariasis treatment: 12 days; W. bancrofti/B. malayi
Uses	Lymphatic filariasis (Wuchereria bancrofti, Brugia malayi), Tropical pulmonary eosinophilia, Loiasis
NOT first-line for Onchocerciasis	Use ivermectin - DEC causes severe Mazzotti reaction in onchocerciasis
Contraindications	Onchocerciasis, loiasis with high microfilaremia
ADR	Mazzotti-like reaction (fever, itching, rash, swelling - from dying microfilariae), headache, GI upset

6. NICLOSAMIDE

Heading: Antihelminthic > Niclosamide (Tapeworm specific) MOA (one line): Inhibits glucose uptake and oxidative phosphorylation in tapeworm - kills the worm - worm is expelled (digested - scolex may not be identified)

Parameter	Detail
Form	Tablets 500 mg (chewable)
Dose	2 g (4 tabs) single dose chewed thoroughly; Pediatric: 11-34 kg: 1 g, > 34 kg: 1.5 g
OPD	YES
Uses	Tapeworms (Taenia saginata - beef tapeworm, Taenia solium - pork tapeworm, Diphyllobothrium latum - fish tapeworm, Hymenolepis nana - dwarf tapeworm)
NOT for cysticercosis	Kills only intestinal adult tapeworm, not larval cysts
Contraindications	None significant
ADR	Nausea, vomiting, abdominal pain, light-headedness

MASTER QUICK-REFERENCE TABLE

Dosing Summary at a Glance

Drug	Form	Dose	Frequency	Duration	OPD/IPD
Penicillin V	Tab 250/500 mg	250-500 mg	QID	7-10 days	OPD
Amoxicillin	Tab/Cap 250/500 mg	250-500 mg	TDS	5-10 days	OPD
Augmentin	Tab 375/625 mg	625 mg	TDS	5-14 days	OPD
Cephalexin	Cap 250/500 mg	250-500 mg	QID	7-10 days	OPD
Cefuroxime	Tab 250/500 mg	250-500 mg	BD	7-10 days	OPD
Ceftriaxone	Inj 1g	1-2 g	OD (BD meningitis)	5-14 days	IPD (IM/OPD mild)
Ciprofloxacin	Tab 500 mg	500 mg	BD	3-14 days	OPD
Levofloxacin	Tab 500/750 mg	500-750 mg	OD	5-14 days	OPD
Doxycycline	Cap 100 mg	100 mg	OD (BD loading 200 mg day 1)	7 days to months	OPD
Azithromycin	Tab 500 mg	500 mg Day1, 250 mg OD	OD	5 days	OPD
Clarithromycin	Tab 250/500 mg	250-500 mg	BD	7-14 days	OPD
Metronidazole	Tab 400 mg	400 mg	TDS	5-14 days	OPD
Co-trimoxazole DS	Tab	1 DS tab	BD	3-14 days	OPD
Rifampicin	Cap 150/300/450/600 mg	450-600 mg	OD	6 months+	OPD (DOTS)
INH	Tab 100/300 mg	300 mg	OD	6 months	OPD (DOTS)
Fluconazole	Cap 150 mg	150 mg	Single dose or OD	Varies	OPD
Albendazole	Tab 400 mg	400 mg	Single dose	1-3 days	OPD
Ivermectin	Tab 3/6 mg	200 mcg/kg	Single dose	1-2 doses	OPD
Oseltamivir	Cap 75 mg	75 mg	BD	5 days	OPD
Acyclovir (HSV)	Tab 200/400/800 mg	400-800 mg	3-5×/day	5-21 days	OPD/IPD
Chloroquine	Tab 150 mg base	600 mg then 300 mg	OD	3 days	OPD
Primaquine	Tab 15 mg	15 mg	OD	14 days	OPD
Vancomycin	Inj 1g	1g	BD (q12h)	7-42 days	IPD (IV)
Gentamicin	Inj 80 mg	5-7 mg/kg	OD	5-7 days	IPD (IV)
Imipenem-cilastatin	Inj 500 mg	500 mg	QID	7-14 days	IPD (ICU)
Amphotericin B	Inj 50 mg	0.3-1.5 mg/kg	OD	Weeks	IPD
Praziquantel	Tab 600 mg	40 mg/kg	Single or TDS	1-2 days	OPD

OPD vs IPD - The Quick Decision Rule

Send to OPD (Oral therapy) when:

Mild to moderate infection
Patient can swallow and absorb oral drugs
Fever < 38.5°C, stable vitals
No vomiting
Reliable to follow up
Non-immunocompromised

Admit to IPD (IV therapy) when:

Sepsis / shock
Cannot tolerate oral drugs (vomiting, unconscious)
Meningitis, endocarditis, osteomyelitis, severe pneumonia
Immunocompromised (HIV, cancer, transplant, steroids)
Failed outpatient therapy
Neonates and very young infants
Fever > 38.5°C with systemic signs
Bacteremia confirmed on blood culture

Contraindications - Master Summary

Drug/Class	Key Contraindication
All Beta-lactams	Penicillin/cephalosporin allergy (anaphylaxis)
Tetracyclines	Children < 8 years, pregnancy, lactation
Aminoglycosides	Pre-existing renal failure, deafness, concurrent nephrotoxins
Fluoroquinolones	Children < 18 years (unless anthrax), pregnancy, QTc prolongation
Chloramphenicol	Neonates (Grey Baby), pregnancy near term, blood dyscrasias
Sulfonamides	Neonates, near-term pregnancy, G6PD deficiency
Metronidazole	1st trimester pregnancy; never with alcohol
Rifampicin	Active hepatic disease; warn about OCP failure
Isoniazid	Previous INH hepatotoxicity (active hepatic disease - caution)
Ethambutol	Optic neuritis, patients unable to report visual changes, young children
Amphotericin B	Severe renal failure (use liposomal form); hypokalemia
Fluconazole	1st trimester pregnancy, QTc-prolonging drug combinations
Griseofulvin	Pregnancy (teratogenic), porphyria
Chloroquine	Retinopathy, G6PD (relative)
Primaquine	G6PD deficiency (hemolysis), pregnancy
Albendazole	Pregnancy
Ivermectin	Weight < 15 kg, pregnancy, CNS disease

Sources: Katzung's Basic and Clinical Pharmacology 16th Edition (Chapters 43-53) + Lippincott Illustrated Reviews: Pharmacology. These cover the full antimicrobial syllabus for MBBS/Internship level. The dosing given follows standard references used in India and internationally (WHO, IDSA guidelines).That is the complete antimicrobial reference. Here is a quick orientation to use it:

How to use this reference during internship:

In OPD - Identify the infection → pick the right section → find the OPD drug → note form, dose, frequency, duration. For most RTIs/UTIs/skin infections you will be using: Amoxicillin, Augmentin, Cephalexin, Ciprofloxacin, Azithromycin, Doxycycline, Metronidazole, Co-trimoxazole, Fluconazole.

In IPD/Wards - The "escalation ladder" is: Ceftriaxone → Pip-Tazo → Meropenem → (add Vancomycin for gram-positive cover + Colistin if pan-resistant). Always have blood cultures BEFORE starting IV antibiotics.

Dose calculations you must know:

Aminoglycosides: mg/kg/day (once daily = 5-7 mg/kg)
Vancomycin: 15-20 mg/kg every 12 hours
Amphotericin B: 0.3-1.5 mg/kg/day
Ivermectin: 200 mcg/kg
All TB drugs: per kg (check weight of patient)

Pediatric rule of thumb: Most antibiotics are given at mg/kg/day. Always divide the total daily dose into the number of doses. For example, amoxicillin 40 mg/kg/day TDS = 40 × weight ÷ 3 = dose per tablet/dose.

U have explain main main antibiotics from each Classification amd heading but I need all for eg in Cephalosporins there are so many I each generation but u have explained only main one I need all means all antimicrobial do not leave any single thing and also mention generic and brand name too and how many tats per strip too and can route of administration too

Finding Sources

Reading File

I now have all the textbook data I need. Let me now write the exhaustive complete reference.

Make a list of uses and Contraindications to learn easily where to use antibiotic and which one and which not

Great question - this is exactly what you need for clinical practice. Let me build this the smartest way possible: disease-first (what infection → which drug) AND drug-first (which drug → avoid when).

Finding Sources

Reading File

Finding Sources

Reading File

I now have all the clinical context I need. Let me write the complete, easy-to-learn reference.

ANTIBIOTIC USES & CONTRAINDICATIONS - THE COMPLETE CLINICAL GUIDE

For Final Year MBBS / Internship - Learn It Once, Use It Forever

PART 1: DISEASE → DRUG (Where to Use Which Antibiotic)

This is how your brain should work in OPD/ward: "What infection is this? Which bug? Which drug?"

🫁 RESPIRATORY TRACT INFECTIONS

Community-Acquired Pneumonia (CAP) - OPD (Mild)

Severity	Drug(s)	Dose / Duration
Mild - OPD	Amoxicillin 500 mg TDS × 5-7 days	If pneumococcal suspected
Mild with atypicals	Azithromycin 500 mg OD × 5 days	Mycoplasma, Chlamydia, Legionella
Mild-Moderate	Amoxicillin + Azithromycin (combo)	Covers both typical + atypical
Alternative OPD	Levofloxacin 750 mg OD × 5 days	Single drug covers everything
Alternative OPD	Doxycycline 100 mg BD × 7 days	Cheap, effective, covers atypicals

CAP - IPD (Moderate-Severe, Hospitalized)

Setting	Drug	Route
Ward (non-ICU)	Ceftriaxone 1-2g IV OD + Azithromycin 500 mg IV/PO OD	IV + oral
ICU	Ceftriaxone 2g IV OD + Levofloxacin 750 mg IV OD	Both IV
Aspiration pneumonia	Pip-Tazo 4.5g IV q6h OR Amoxicillin-Clavulanate + Metronidazole	IV
Pseudomonas suspected	Ceftazidime 2g IV q8h OR Pip-Tazo + Ciprofloxacin	IV
MRSA pneumonia	Vancomycin 1g IV BD + Ceftriaxone	IV

Atypical Pneumonia (Mycoplasma, Chlamydia, Legionella)

DOC: Azithromycin OR Doxycycline OR Levofloxacin/Moxifloxacin
Beta-lactams DO NOT work against atypicals (no cell wall target)

Hospital-Acquired Pneumonia (HAP)

Pip-Tazo 4.5g IV q6h + Vancomycin (if MRSA risk)
Or Meropenem 1-2g IV q8h (MDR organisms)

Lung Abscess / Aspiration

Amoxicillin-Clavulanate 1.2g IV q8h (ward)
Metronidazole 500 mg IV TDS + Ceftriaxone (covers both anaerobes + GN)
Clindamycin 600 mg IV q8h (alternative - excellent for anaerobes)

Whooping Cough (Pertussis - Bordetella)

DOC: Azithromycin 500 mg OD × 5 days (all ages; infant: 10 mg/kg OD)
Alternative: Erythromycin, Co-trimoxazole

Tuberculosis (Pulmonary)

Phase	Drugs	Duration
Intensive	Isoniazid + Rifampicin + Pyrazinamide + Ethambutol (HRZE)	2 months
Continuation	Isoniazid + Rifampicin (HR)	4 months
Total		6 months

🧠 CNS INFECTIONS

Bacterial Meningitis

Age / Setting	Likely Organism	Drug of Choice
Neonate (< 3 months)	Group B Strep + Listeria + E. coli	Ampicillin 200 mg/kg/day IV + Cefotaxime 200 mg/kg/day IV
Children (3 mo - 5 yrs)	Pneumococcus + Meningococcus + H. influenzae	Ceftriaxone 100 mg/kg/day IV BD
Adults (5-50 yrs)	Pneumococcus + Meningococcus	Ceftriaxone 2g IV BD + Vancomycin 1g IV q8h
Elderly / Immunocomp.	Listeria + Pneumococcus	Ceftriaxone 2g IV BD + Ampicillin 2g IV q4h
Add always	Dexamethasone 0.15 mg/kg IV q6h × 4 days	Given 15-20 min BEFORE antibiotics to reduce inflammation

Duration: Meningococcal: 7 days; Pneumococcal: 10-14 days; Listeria: 21 days

Brain Abscess

Ceftriaxone 2g IV BD + Metronidazole 500 mg IV TDS
Duration: 4-8 weeks (often needs surgical drainage)

Herpes Encephalitis

DOC: Acyclovir 10 mg/kg IV TDS × 14-21 days (start IMMEDIATELY - don't wait for PCR)

Meningococcal Prophylaxis (Contacts)

Rifampicin 600 mg BD × 2 days (adults) OR Ciprofloxacin 500 mg single dose

💛 URINARY TRACT INFECTIONS (UTI)

Uncomplicated UTI (Young women, no fever, no flank pain)

Drug	Dose	Duration
Co-trimoxazole DS	1 tablet BD	3 days
Ciprofloxacin	250-500 mg BD	3 days
Nitrofurantoin	100 mg BD (modified release)	5 days
Fosfomycin	3g sachet single dose	1 day only
Cephalexin	500 mg QID	7 days

Complicated UTI / Pyelonephritis (Fever + flank pain)

Setting	Drug	Route	Duration
OPD - mild	Ciprofloxacin 500 mg BD	PO	7-14 days
OPD - mild	Levofloxacin 750 mg OD	PO	5-7 days
IPD	Ceftriaxone 1-2g IV OD	IV	7-14 days
IPD - severe	Pip-Tazo 4.5g IV q6h	IV	10-14 days

Catheter-Associated UTI (CAUTI)

Remove catheter if possible
Ceftriaxone IV or Ciprofloxacin PO × 7-14 days

Recurrent UTI Prophylaxis

Co-trimoxazole SS 1 tab OD at night × 6 months
Nitrofurantoin 50-100 mg OD at night × 6 months

🦠 SKIN AND SOFT TISSUE INFECTIONS

Impetigo / Minor Skin Infections

Topical Mupirocin (Bactroban) cream 3×/day × 5-7 days
Oral: Cephalexin 500 mg QID × 7 days

Cellulitis (No pus, No MRSA risk)

DOC: Amoxicillin-Clavulanate 625 mg TDS × 7-10 days (OPD)
Or Cephalexin 500 mg QID × 7-10 days
IPD severe: Ceftriaxone 1-2g IV OD × 5-7 days

Cellulitis + Abscess (Pus present, MRSA possible)

Drain pus surgically first
Co-trimoxazole DS 1 tab BD × 5-7 days (covers CA-MRSA)
Or Doxycycline 100 mg BD × 5-7 days

Necrotizing Fasciitis (Surgical emergency!)

Surgery FIRST + Pip-Tazo 4.5g IV q6h + Metronidazole 500 mg IV TDS + Vancomycin 1g IV q12h
Duration: Until debridement complete + clinical improvement

Diabetic Foot Infection

Severity	Drug
Mild (superficial)	Amoxicillin-Clavulanate 625 mg TDS (OPD)
Moderate	Pip-Tazo 4.5g IV q6h OR Amp-Sulbactam IV
Severe / Osteomyelitis	Meropenem + Vancomycin IV × 4-6 weeks

Animal / Human Bite Wounds

DOC: Amoxicillin-Clavulanate (Augmentin) 625 mg TDS × 5-7 days
Covers Pasteurella (dog/cat), Capnocytophaga, oral anaerobes
Penicillin allergy: Doxycycline or Co-trimoxazole + Metronidazole

❤️ CARDIOVASCULAR / HEART

Infective Endocarditis

Organism	Drugs	Duration
Streptococcal (viridans)	Benzylpenicillin 2 MU IV q4h + Gentamicin 1 mg/kg IV TDS	4-6 weeks
Staphylococcal (MSSA)	Flucloxacillin/Nafcillin 2g IV q4h	4-6 weeks
Staphylococcal (MRSA)	Vancomycin 1g IV q12h	6 weeks
Enterococcal	Ampicillin 2g IV q4h + Gentamicin (synergy)	4-6 weeks
Prosthetic valve MRSA	Vancomycin + Rifampicin + Gentamicin	6+ weeks

Rheumatic Fever Prophylaxis

Benzathine Penicillin G 1.2 MU IM once every 3-4 weeks
Duration: 5-10 years (or lifelong if carditis present)

🦷 ENT & DENTAL INFECTIONS

Pharyngitis / Strep Throat (Group A Strep)

DOC: Amoxicillin 500 mg TDS × 10 days
Or Penicillin V 500 mg BD × 10 days (10 days needed to eradicate GAS!)
Penicillin allergy: Azithromycin 500 mg OD × 5 days OR Cephalexin

Otitis Media (AOM) - Children

Amoxicillin 80-90 mg/kg/day TDS × 10 days (high dose for resistant pneumococcus)
Amoxicillin-Clavulanate if fails after 48-72 hours

Sinusitis (Bacterial)

Amoxicillin-Clavulanate 625 mg TDS × 5-7 days
Or Doxycycline 100 mg BD × 7 days (penicillin allergy)
Amoxicillin alone if mild and local resistance is low

Dental Abscess

Amoxicillin-Clavulanate 625 mg TDS × 5-7 days
Or Metronidazole 400 mg TDS + Amoxicillin 500 mg TDS × 5 days
Penicillin allergy: Clindamycin 300 mg QID × 5 days (excellent for dental infections + anaerobes)

Peritonsillar Abscess

Benzylpenicillin IV + Metronidazole IV (drain first!)

🍽️ GASTROINTESTINAL INFECTIONS

Typhoid Fever (Salmonella typhi)

Drug	Dose	Duration	Notes
Ciprofloxacin	500 mg BD	7-14 days	OPD mild
Ceftriaxone	2g IV OD	10-14 days	IPD moderate-severe
Azithromycin	500 mg OD	7 days	Children, pregnant, resistance
Chloramphenicol	50 mg/kg/day QID	14 days	Only if susceptible (less used)

Shigellosis (Dysentery)

Ciprofloxacin 500 mg BD × 3-5 days
Azithromycin 500 mg OD × 3 days (resistant or children)
Co-trimoxazole DS BD × 5 days (if susceptible)

Cholera (Vibrio cholerae)

ORS is the MAIN treatment
Doxycycline 300 mg single dose (adults)
Azithromycin 1g single dose (children, pregnant)
Ciprofloxacin 1g single dose

H. pylori Eradication

Regimen	Drugs	Duration
Standard Triple Therapy	PPI BD + Amoxicillin 1g BD + Clarithromycin 500 mg BD	14 days
Bismuth Quadruple	PPI + Bismuth + Tetracycline + Metronidazole	14 days (for resistant)
Penicillin allergy	PPI + Metronidazole 400 mg TDS + Clarithromycin 500 mg BD	14 days

C. difficile Colitis (After antibiotics)

Severity	Drug	Route	Duration
Mild-Moderate	Metronidazole 500 mg TDS	PO	10-14 days
Severe	Vancomycin 125 mg QID	PO (oral - NOT IV)	10 days
Recurrent	Fidaxomicin 200 mg BD	PO	10 days
Multiple recurrences	Fecal microbiota transplant (FMT)

Amoebic Dysentery (Entamoeba histolytica)

Metronidazole 400-800 mg TDS × 7-10 days (kills tissue amoeba)
THEN Diloxanide Furoate 500 mg TDS × 10 days (kills luminal cysts)

Giardiasis

DOC: Metronidazole 400 mg TDS × 5-7 days
Alternative: Tinidazole 2g single dose (simpler, more convenient)

Traveller's Diarrhea

Azithromycin 500 mg OD × 3 days (most areas, especially South Asia - best)
Ciprofloxacin 500 mg BD × 3 days (if Azithromycin unavailable)
Rifaximin 200 mg TDS × 3 days (non-invasive, not absorbed - no systemic side effects)

🧬 SEXUALLY TRANSMITTED INFECTIONS (STIs)

Gonorrhea (Neisseria gonorrhoeae)

DOC: Ceftriaxone 500 mg IM single dose (resistance to oral drugs increasing)
Add Azithromycin 1g PO single dose (to cover co-existing Chlamydia)

Chlamydia (Chlamydia trachomatis)

DOC: Azithromycin 1g PO single dose (single dose - ensures compliance)
Alternative: Doxycycline 100 mg BD × 7 days
Pregnancy: Azithromycin 1g single dose (safe in pregnancy)

Syphilis

Stage	Drug	Dose
Primary / Secondary	Benzathine Penicillin G	2.4 MU IM single dose
Latent (< 1 year)	Benzathine Penicillin G	2.4 MU IM single dose
Latent (> 1 year) / Late	Benzathine Penicillin G	2.4 MU IM weekly × 3 doses
Neurosyphilis	Benzylpenicillin G	3-4 MU IV q4h × 10-14 days
Penicillin allergy	Doxycycline	100 mg BD × 14-28 days

PID (Pelvic Inflammatory Disease)

OPD: Ceftriaxone 500 mg IM single dose + Doxycycline 100 mg BD + Metronidazole 400 mg BD × 14 days
IPD: Cefoxitin 2g IV q6h + Doxycycline 100 mg PO BD × 14 days
Or: Clindamycin 900 mg IV q8h + Gentamicin 2 mg/kg IV loading then 1.5 mg/kg q8h

Trichomoniasis

Metronidazole 2g PO single dose (TREAT BOTH PARTNERS)
Or Tinidazole 2g PO single dose

Bacterial Vaginosis

Metronidazole 400 mg BD × 7 days (PO)
Or Metronidazole gel intravaginally BD × 5 days
Or Clindamycin cream 2% intravaginally OD × 7 days

🦴 BONE AND JOINT INFECTIONS

Osteomyelitis

Organism	Drug	Route	Duration
MSSA (most common)	Flucloxacillin 2g IV q4-6h → switch to oral Clindamycin/Flucloxacillin	IV then PO	4-6 weeks total
MRSA	Vancomycin 1g IV q12h → Linezolid PO	IV then PO	4-6 weeks
Gram-negative	Ceftriaxone 2g IV OD	IV	4-6 weeks
Salmonella (sickle cell)	Ciprofloxacin 500 mg BD	PO	4-6 weeks

Septic Arthritis

Flucloxacillin 2g IV q6h (MSSA) OR Vancomycin (MRSA)
Drain joint + antibiotics × 2-4 weeks

👶 NEONATAL / PEDIATRIC INFECTIONS

Neonatal Sepsis (Early onset < 72 hours)

Ampicillin 100-200 mg/kg/day IV q12h + Gentamicin 4-7 mg/kg IV OD

Neonatal Meningitis

Cefotaxime 150-200 mg/kg/day IV q6-8h + Ampicillin (for Listeria coverage)

Neonatal Conjunctivitis (Gonococcal)

Ceftriaxone 25-50 mg/kg IM single dose (max 125 mg)

💉 SEPSIS / SEPTIC SHOCK (EMPIRIC)

GOLDEN RULE: Take blood cultures FIRST, then start antibiotics within 1 hour

Source	Empiric Drug Regimen
Unknown source	Pip-Tazo 4.5g IV q6h + Vancomycin 1g IV q12h
Urinary source	Ceftriaxone 2g IV OD OR Pip-Tazo 4.5g IV q6h
Abdominal source	Pip-Tazo 4.5g IV q6h + Metronidazole 500 mg IV q8h
Respiratory source	Ceftriaxone 2g IV OD + Azithromycin 500 mg IV OD
Skin source	Flucloxacillin 2g IV q6h OR Vancomycin (MRSA)
MDR suspected / ICU	Meropenem 1-2g IV q8h + Vancomycin 1g IV q12h

🌿 TUBERCULOSIS / MYCOBACTERIAL

Disease	Regimen	Duration
Drug-sensitive TB	HRZE × 2 months → HR × 4 months	6 months
TB Meningitis	HRZE × 2 months → HR × 10 months + Dexamethasone	12 months
Latent TB	INH 300 mg OD + Pyridoxine 25 mg OD	6-9 months
MDR-TB	Specialist-guided regimen (Bedaquiline, Linezolid, Levofloxacin)	18-24 months
MAC (in HIV)	Clarithromycin 500 mg BD + Ethambutol + Rifabutin	Lifelong
Leprosy - PB	Rifampicin 600 mg monthly + Dapsone 100 mg OD	6 months
Leprosy - MB	Rifampicin 600 mg monthly + Dapsone 100 mg OD + Clofazimine	12 months

🦠 FUNGAL INFECTIONS

Infection	Drug	Dose	Route
Vaginal candidiasis	Fluconazole 150 mg	Single dose	PO
Oral thrush	Nystatin drops OR Fluconazole 100 mg OD × 7-14 days		PO
Esophageal candidiasis	Fluconazole 200-400 mg OD × 14-21 days		PO/IV
Candidemia (ICU)	Caspofungin 70 mg loading → 50 mg OD		IV
Invasive Aspergillosis	Voriconazole 6 mg/kg IV BD Day 1 → 4 mg/kg BD		IV
Cryptococcal meningitis	AmBisome 3-5 mg/kg OD × 2 weeks → Fluconazole 400 mg OD × 8 weeks → 200 mg OD lifelong		IV then PO
Mucormycosis	Liposomal AmB 5-10 mg/kg OD + Surgery		IV
Ringworm (skin)	Terbinafine cream 1% BD × 2-4 weeks		Topical
Nail fungus (onychomycosis)	Terbinafine 250 mg OD × 6 weeks (finger) / 12 weeks (toe)		PO
Tinea capitis (scalp)	Griseofulvin 500 mg OD × 4-6 weeks with fatty meal		PO
Tinea versicolor	Ketoconazole shampoo × 3 days OR Fluconazole 300 mg × 2 doses (1 week apart)		Topical/PO

🦟 MALARIA

Type	Drug	Dose
Uncomplicated P. falciparum	Artemether-Lumefantrine (Coartem)	4 tabs BD × 3 days (with food)
P. vivax / P. ovale / P. malariae	Chloroquine 600 mg → 300 mg day 2 → 300 mg day 3 THEN Primaquine 15 mg OD × 14 days (check G6PD first)	PO
Severe malaria	IV Artesunate 2.4 mg/kg at 0, 12, 24h then OD	IV
Malaria prophylaxis	Doxycycline 100 mg OD (start 1-2 days before travel, continue 4 wks after)	PO

🪱 PARASITIC / WORM INFECTIONS

Infection	Drug of Choice	Dose
Roundworm (Ascaris)	Albendazole 400 mg	Single dose
Hookworm	Albendazole 400 mg	Single dose
Pinworm (Enterobius)	Albendazole 400 mg	Single dose, repeat in 2 weeks
Whipworm (Trichuris)	Albendazole 400 mg OD × 3 days	3 days
Strongyloides	Ivermectin 200 mcg/kg OD × 2 days	2 days
Tapeworm (Taenia)	Praziquantel 5-10 mg/kg	Single dose
Schistosomiasis	Praziquantel 40 mg/kg	Single dose (S. haematobium/mansoni)
Filariasis	DEC 6 mg/kg OD + Albendazole 400 mg	Once yearly (MDA)
Neurocysticercosis	Albendazole 400 mg BD × 8-30 days + Dexamethasone + Antiepileptics
Hydatid cyst	Albendazole 400 mg BD × 28 days × 3 cycles	Pre/post surgery
Scabies	Ivermectin 200 mcg/kg + repeat in 2 weeks OR Permethrin 5% cream

PART 2: DRUG → CONTRAINDICATIONS (When NOT to Use)

🚫 PENICILLINS (All - Penicillin G/V, Ampicillin, Amoxicillin, Flucloxacillin, Pip-Tazo)

Contraindication	Reason
History of penicillin anaphylaxis	Cross-reacts with all penicillins; may cross-react with cephalosporins
Infectious mononucleosis (EBV)	Ampicillin/Amoxicillin causes 100% rash (not a true allergy but always happens)
-	-
Use with CAUTION in:
Mild penicillin allergy (rash only)	Can use cephalosporins (3-5% cross-reactivity)
Severe renal failure	Reduce dose of renally-cleared penicillins

🚫 CEPHALOSPORINS

Contraindication	Reason
History of anaphylaxis to penicillin	Risk of cross-reaction (rare but serious)
Previous anaphylaxis to any cephalosporin	Absolute contraindication
Neonates with jaundice (Ceftriaxone)	Displaces bilirubin from albumin → risk of kernicterus
Ceftriaxone with calcium-containing IV fluids in neonates	Precipitates in lungs/kidneys → fatal
Ceftriaxone in biliary obstruction	Excreted in bile → biliary sludge/pseudolithiasis

🚫 CARBAPENEMS (Imipenem, Meropenem, Ertapenem)

Contraindication	Reason
Carbapenem allergy	Absolute
Imipenem in seizure history	Most epileptogenic carbapenem - use meropenem instead
Imipenem in meningitis	Seizure risk at high concentrations - prefer meropenem
Ertapenem in Pseudomonas infections	Ertapenem has NO Pseudomonas coverage

🚫 AMINOGLYCOSIDES (Gentamicin, Amikacin, Tobramycin, Streptomycin)

Contraindication	Reason
Pre-existing renal failure	Nephrotoxic - accumulates
Pre-existing sensorineural hearing loss	Ototoxic - irreversible cochlear damage
Concurrent nephrotoxic drugs (Vancomycin, NSAIDs, Amphotericin B)	Additive nephrotoxicity
Myasthenia gravis	Neuromuscular blockade worsens weakness
Pregnancy	Ototoxic to fetus (cochlear damage)
Anaerobic infections	Not activated without oxygen - useless
Never monotherapy	Always combine with beta-lactam (synergy + prevent resistance)

🚫 TETRACYCLINES (Tetracycline, Doxycycline, Minocycline)

Contraindication	Reason
Children under 8 years	Deposits in developing teeth → yellow-grey discoloration (permanent) and inhibits bone growth
Pregnancy (all trimesters)	Teratogenic, dental staining in fetus
Lactation	Passes into breast milk → infant teeth/bone effects
Severe hepatic failure	Hepatotoxic - concentrate in liver
Severe renal failure (plain tetracycline only)	Can worsen renal function; Doxycycline is safe in renal failure - preferred
Avoid with: Antacids, Ca²⁺, Mg²⁺, Fe²⁺, dairy	2-hour gap - chelation reduces absorption by 90%

🚫 MACROLIDES (Erythromycin, Azithromycin, Clarithromycin, Roxithromycin)

Contraindication	Reason
Long QTc interval (> 450 ms men, > 470 ms women)	Macrolides prolong QTc → Torsades de Pointes → sudden death
Concurrent QTc-prolonging drugs (antipsychotics, antiarrhythmics, other antibiotics)	Additive QTc prolongation
Hepatic failure (severe)	Metabolized by liver (especially erythromycin, clarithromycin)
Erythromycin + Theophylline	Increases theophylline levels → toxicity (seizures, arrhythmias)
Erythromycin + Statins	Myopathy risk (CYP3A4 inhibition)
Clarithromycin + Carbamazepine	Seizure risk (CYP interaction)
Azithromycin is safest in: Pregnancy, renal failure, few drug interactions

🚫 CHLORAMPHENICOL

Contraindication	Reason
Neonates and premature infants	Grey Baby Syndrome - cannot conjugate drug - accumulates → cardiovascular collapse, death
Pregnancy (near term)	Drug crosses placenta → Grey Baby in neonate
Lactation	Passes into breast milk
Previous blood dyscrasias	Bone marrow suppression / aplastic anemia history
Concurrent bone marrow suppressive drugs	Additive bone marrow toxicity
Do NOT use for trivial infections	Risk of aplastic anemia (1:25,000) does not justify routine use

🚫 CLINDAMYCIN

Contraindication	Reason
History of Clindamycin-associated colitis	Previous C. difficile colitis
History of pseudomembranous colitis (ANY antibiotic)	High risk of recurrence
Diarrheal illness in progress	Could be starting C. difficile - do not add clindamycin
Meningitis	Does NOT penetrate CSF adequately
STOP immediately if patient develops diarrhea during treatment	Could be C. difficile - most dangerous complication

🚫 FLUOROQUINOLONES (Ciprofloxacin, Levofloxacin, Moxifloxacin, Ofloxacin, Norfloxacin)

Contraindication	Reason
Children under 18 years	Damage to growing cartilage (arthropathy in animal studies) - EXCEPTION: anthrax, inhalation exposure
Pregnancy and lactation	Teratogenic, cartilage effects in fetus
History of tendon rupture with fluoroquinolones	Very high risk of recurrence
Long QTc interval	QTc prolongation → arrhythmias (especially Moxifloxacin)
Epilepsy / seizure history	Lower seizure threshold - CNS toxicity
Moxifloxacin for UTI	Insufficient urinary concentrations - does NOT work for UTI
Norfloxacin for systemic infections	Poor systemic bioavailability - only for gut/UTI
Caution with:	Concurrent NSAIDs (seizure risk), Antacids/iron/calcium (chelation - give 2 hours apart), Theophylline, Warfarin
Black box warnings (USA/India):	Tendinopathy, tendon rupture, peripheral neuropathy, CNS effects, aortic aneurysm risk

🚫 SULFONAMIDES / CO-TRIMOXAZOLE (TMP-SMX)

Contraindication	Reason
Neonates under 2 months	Kernicterus - sulfonamides displace bilirubin from albumin → brain damage → death
Near-term pregnancy (3rd trimester)	Neonatal kernicterus, neonatal jaundice
First trimester pregnancy	Trimethoprim is folate antagonist → neural tube defects
G6PD deficiency	Hemolytic anemia
Severe renal failure	Accumulation and crystalluria
Severe hepatic failure	Poor metabolism
Megaloblastic anemia	Trimethoprim worsens folate deficiency
Avoid with:	Methotrexate (bone marrow suppression × 2), Warfarin (potentiates anticoagulation)

🚫 METRONIDAZOLE

Contraindication	Reason
ABSOLUTE: ALCOHOL	Disulfiram-like reaction (acetaldehyde accumulates) → severe flushing, vomiting, hypotension, potentially fatal. No alcohol during treatment AND 48 hours after
First trimester pregnancy	Theoretical teratogenicity (animal data) - avoid if possible; weigh risk vs benefit
Neurological diseases (peripheral neuropathy, seizures)	Worsens neurological symptoms
Previous hypersensitivity to nitroimidazoles	Cross-reacts with tinidazole, ornidazole
Caution with:	Warfarin (increases anticoagulant effect - monitor INR), Lithium, Phenytoin

🚫 RIFAMPICIN

Contraindication	Reason
Active severe hepatic disease / acute jaundice	Hepatotoxic - metabolized by liver
Previous rifampicin-induced hepatitis	High risk of recurrence
NEVER use alone	Rapid resistance develops within 7-10 days (always combine)
Drug interactions (CRITICAL):
Oral Contraceptive Pill (OCP)	CYP450 inducer → reduces OCP levels → PREGNANCY risk. Use barrier contraception
Warfarin	Reduces anticoagulant effect → increase warfarin dose, monitor INR
HIV antiretrovirals (most)	Reduces drug levels → treatment failure
Corticosteroids	Reduces steroid effect
Antiepileptics (phenytoin, carbamazepine)	Reduces levels
Sulfonylureas, antifungals, calcium channel blockers	Reduces all their levels

🚫 ISONIAZID (INH)

Contraindication	Reason
Active hepatic disease / elevated LFTs (> 3× normal)	Hepatotoxic
Previous INH-induced liver damage	High risk of recurrence
Known hypersensitivity
Always co-prescribe:	Pyridoxine (Vitamin B6) 10-25 mg OD - prevents peripheral neuropathy
Caution with:	Alcohol (hepatotoxicity × 2), Phenytoin (increased phenytoin toxicity), Antacids (reduce INH absorption)

🚫 VANCOMYCIN

Contraindication	Reason
Known vancomycin allergy
Infusion faster than 60 minutes	Red Man Syndrome (histamine release) → severe flushing, hypotension, erythema. NOT a true allergy
Concurrent aminoglycosides	Additive nephrotoxicity and ototoxicity
Pre-existing hearing loss	Ototoxic
Oral vancomycin for systemic infections	Not absorbed orally - only use oral form for C. difficile in gut
Monitor:	Renal function (creatinine), trough levels (target 10-20 mcg/mL) - every 2-3 days

🚫 AMPHOTERICIN B (Conventional)

Contraindication	Reason
Severe renal failure	Highly nephrotoxic - use liposomal form (AmBisome) instead
Hypokalemia (K⁺ < 3.0 mmol/L)	Worsens potassium depletion - correct first
Concurrent nephrotoxic drugs	Additive nephrotoxicity
NEVER give rapid IV push	Cardiac arrhythmias, hypotension, death - always infuse over 2-6 hours
Always pre-medicate	Paracetamol + Antihistamine + Hydrocortisone 1 hour before infusion

🚫 FLUCONAZOLE

Contraindication	Reason
First trimester pregnancy	Teratogenic (especially repeated/high doses)
Long QTc	QTc prolongation
Severe hepatic disease	Metabolized by liver
Drug interactions:
Warfarin	CYP2C9 inhibition → increases warfarin → bleeding risk (reduce warfarin dose)
Statins (simvastatin, atorvastatin)	Myopathy risk (CYP3A4 inhibition)
Cisapride, terfenadine	Dangerous QTc prolongation
Sulfonylureas	Hypoglycemia (increased levels)

🚫 GRISEOFULVIN

Contraindication	Reason
Pregnancy	Teratogenic
Porphyria	Triggers acute porphyria attack
Severe hepatic disease
Drug interactions:	Alcohol (disulfiram-like reaction), Warfarin (reduces anticoagulant effect), OCP (reduces efficacy)

🚫 CHLOROQUINE / ANTIMALARIALS

Drug	Contraindication	Reason
Chloroquine	Retinal / visual field disease	Causes retinopathy (long-term)
Chloroquine	Psoriasis	Triggers flare
Primaquine	G6PD deficiency	Severe hemolytic anemia (can be fatal)
Primaquine	Pregnancy	Fetal G6PD status unknown - hemolysis risk
Mefloquine	Psychiatric illness, seizure history	Neuropsychiatric toxicity
Doxycycline (prophylaxis)	Children under 8, pregnancy	Dental/bone effects
Quinine	G6PD deficiency, heart disease (QTc)	Hemolysis, arrhythmias

🚫 ALBENDAZOLE / MEBENDAZOLE

Contraindication	Reason
Pregnancy (especially 1st trimester)	Teratogenic (animal data) - confirm not pregnant before prescribing
Under 1 year of age	Safety not established
Ocular cysticercosis	Killing the worm in the eye causes intense inflammation → blindness
Albendazole alone for neurocysticercosis	Must ALWAYS give with steroids (dexamethasone) to suppress die-off inflammation

🚫 IVERMECTIN

Contraindication	Reason
Weight under 15 kg (children)	Safety not established
Pregnancy	Safety not established
Meningitis / blood-brain barrier disruption	Ivermectin enters CNS → neurotoxicity
Concurrent drugs that inhibit P-glycoprotein	Increased CNS penetration → neurotoxicity
Onchocerciasis with high microfilarial load + Loiasis co-infection	Severe Mazzotti reaction → encephalopathy

PART 3: SPECIAL SITUATION GUIDE - "Which antibiotic in...?"

IN PREGNANCY 🤰 - SAFE VS AVOID

SAFE (Use Freely)	CAUTION	AVOID
Penicillins (all)	Metronidazole (2nd/3rd trimester OK, avoid 1st)	Tetracyclines
Cephalosporins (all)	Chloroquine (low dose OK)	Fluoroquinolones
Azithromycin	Clindamycin (OK in 2nd/3rd trimester)	Aminoglycosides
Erythromycin	Nitrofurantoin (avoid at term)	Co-trimoxazole (at term)
Clindamycin (2nd/3rd trimester)		Chloramphenicol (at term)
Ampicillin		Rifampicin (1st trimester)
Ceftriaxone		Streptomycin

Quick rule: Penicillins and Cephalosporins = ALWAYS SAFE in pregnancy

IN CHILDREN - SAFE VS AVOID

AVOID	Age Limit	Reason
Tetracyclines	Under 8 years	Teeth staining, bone growth impairment
Fluoroquinolones	Under 18 years	Cartilage damage (except anthrax)
Chloramphenicol	Neonates	Grey Baby Syndrome
Sulfonamides	Under 2 months	Kernicterus
Primaquine	Under 6 months (check G6PD)	Hemolysis

Safe in children: Amoxicillin, Cephalexin, Ceftriaxone, Azithromycin, Co-trimoxazole (> 2 months), Metronidazole, Albendazole (> 1 year), Ivermectin (> 15 kg)

IN RENAL FAILURE - DOSE ADJUST OR AVOID

Drug	Action
Aminoglycosides	AVOID or extend dosing interval; monitor levels closely
Vancomycin	Extend interval; monitor levels (trough)
Ciprofloxacin	Reduce dose by 50% if severe
Co-trimoxazole	Reduce dose (50% if CrCl 15-30; avoid if < 15)
Nitrofurantoin	AVOID (CrCl < 45) - no urinary concentration; causes peripheral neuropathy
Conventional AmB	Use Liposomal AmB instead
Ceftriaxone	NO dose adjustment (biliary excretion) - safe
Doxycycline	NO dose adjustment (safest tetracycline in renal failure)
Metronidazole	No dose adjustment for short courses
Azithromycin	No dose adjustment

IN HEPATIC FAILURE

Drug	Action
Rifampicin	Reduce dose; monitor LFTs; avoid in severe hepatic failure
Isoniazid	Monitor LFTs; stop if > 3× normal with symptoms
Pyrazinamide	Avoid in severe hepatic failure (most hepatotoxic anti-TB drug)
Chloramphenicol	Avoid - accumulates
Metronidazole	Reduce dose in severe liver disease
Doxycycline	Caution in severe disease
Ketoconazole (systemic)	Avoid - highly hepatotoxic
Penicillins, Cephalosporins	Safe - minimal hepatic metabolism
Azithromycin	Caution only in severe disease

IN G6PD DEFICIENCY - DRUGS TO AVOID

Drug	Effect
Primaquine	SEVERE hemolytic anemia (absolute contraindication)
Sulfonamides (TMP-SMX)	Hemolysis
Dapsone	Hemolysis, methemoglobinemia
Nitrofurantoin	Hemolysis
Chloroquine	Mild hemolysis (relative - usually tolerated)
Quinine	Hemolysis, blackwater fever

DRUG OF CHOICE (DOC) QUICK LIST ⭐

Infection	DOC
MRSA	Vancomycin IV (severe) / TMP-SMX or Doxycycline (skin)
Strep throat	Amoxicillin / Penicillin V
Syphilis	Benzathine Penicillin G IM
Neurosyphilis	Penicillin G IV
Gonorrhea	Ceftriaxone 500 mg IM
Chlamydia	Azithromycin 1g single dose
TB	Isoniazid + Rifampicin (backbone)
Leprosy	Multi-drug therapy (Rifampicin + Dapsone ± Clofazimine)
Meningococcal meningitis	Ceftriaxone 2g IV BD
Pneumococcal meningitis	Ceftriaxone + Vancomycin
Listeria meningitis	Ampicillin IV
Typhoid	Ciprofloxacin OR Ceftriaxone (IPD)
Rickettsia	Doxycycline
Chlamydia pneumonia / Mycoplasma	Azithromycin / Doxycycline
Legionella	Azithromycin / Levofloxacin
Pertussis	Azithromycin
Lyme disease	Doxycycline
Giardia	Metronidazole / Tinidazole
Amoebic liver abscess	Metronidazole then Diloxanide furoate
Trichomoniasis	Metronidazole 2g single dose
C. difficile colitis	Oral Vancomycin (severe) / Metronidazole (mild)
Surgical prophylaxis	Cefazolin 1-2g IV single dose
Candidal vaginitis	Fluconazole 150 mg single dose
Cryptococcal meningitis	AmBisome → Fluconazole
Invasive Aspergillosis	Voriconazole
Mucormycosis	Liposomal AmB + Surgery
Herpes simplex	Acyclovir
Herpes encephalitis	Acyclovir IV
CMV retinitis	Ganciclovir / Valganciclovir
Influenza	Oseltamivir (within 48 hours)
P. falciparum malaria	Artemether-Lumefantrine (uncomplicated)
Severe malaria	IV Artesunate
P. vivax / relapse prevention	Chloroquine + Primaquine
Ascaris / Hookworm	Albendazole 400 mg single dose
Strongyloides	Ivermectin
Schistosomiasis	Praziquantel
Tapeworm	Praziquantel
Filariasis	DEC + Albendazole

Remember the clinical thinking process:

What is the likely bug? (Gram +ve / -ve / atypical / anaerobe / fungus / parasite?)

What site? (Can the drug reach there? - CNS, bone, abscess, urine)

Who is the patient? (Age, pregnancy, renal/liver function, allergies, G6PD)

How sick? (OPD oral vs IPD IV)

Any drug interactions?

Sources: Katzung 16th Ed Chapter 51 "Clinical Use of Antimicrobial Agents" + Lippincott Illustrated Reviews Pharmacology, WHO treatment guidelines

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