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Here are complete answers for all questions from both Batch A and Batch B:

FA Structured Long Questions - BATCH A (01/06/2026)

Q1. Classify Anti-malarial drugs. Mention the mechanism of action, therapeutic uses and adverse drug reactions of Chloroquine. (10 marks)

Classification of Anti-malarial Drugs

A. Based on the stage of parasite life cycle:

1. Blood Schizonticides (act on erythrocytic stage):

4-Aminoquinolines: Chloroquine, Amodiaquine
Arylaminoalcohols: Quinine, Mefloquine, Lumefantrine
Artemisinin compounds: Artesunate, Artemether, Arteether
Antifolates: Pyrimethamine, Proguanil
Atovaquone

2. Tissue Schizonticides (act on pre-/exo-erythrocytic stage):

Primaquine, Tafenoquine (also gametocidal)
Proguanil (causal prophylaxis)

3. Gametocytocides:

Primaquine (P. falciparum)
Chloroquine (P. vivax, P. malariae)

4. Hypnozoitocides (against dormant liver forms of P. vivax/P. ovale):

Primaquine, Tafenoquine

Chloroquine

Mechanism of Action: Chloroquine is a weak base that accumulates in the acidic food vacuole of the plasmodium parasite. It inhibits the enzyme heme polymerase, thereby blocking the polymerization of toxic heme (ferriprotoporphyrin IX) into non-toxic hemozoin (malaria pigment). This leads to accumulation of free heme, which is toxic to the parasite, causing membrane damage and parasite death.

Therapeutic Uses:

Treatment of uncomplicated P. vivax, P. malariae, and P. ovale malaria
Prophylaxis of malaria in chloroquine-sensitive areas
Radical cure of P. vivax (combined with primaquine)
Rheumatoid arthritis and Systemic Lupus Erythematosus (SLE) - as a DMARD
Amoebic liver abscess (second line, after metronidazole)
Infectious mononucleosis
Lepra reactions (mild anti-inflammatory effect)

Adverse Drug Reactions:

System	ADR
GI	Nausea, vomiting, abdominal pain, diarrhea
CNS	Headache, dizziness, insomnia, psychosis (rare)
Eyes	Corneal deposits (reversible), retinopathy (irreversible - most serious, dose-dependent)
Skin	Pruritus (especially in dark-skinned individuals), bleaching of hair, exfoliative dermatitis
Cardiovascular	QT prolongation, arrhythmias (at high doses)
Blood	Hemolytic anemia in G6PD deficiency
Musculoskeletal	Myopathy, cardiomyopathy (long-term use)

Contraindications: Retinal/visual field changes, psoriasis, porphyria, G6PD deficiency (relative)

Q2. Classify Penicillins. Mention the mechanism of drug resistance to Penicillins. Write about Anti-Pseudomonal Penicillins. (10 marks)

Classification of Penicillins

1. Natural Penicillins:

Penicillin G (Benzylpenicillin) - parenteral
Penicillin V (Phenoxymethylpenicillin) - oral

2. Penicillinase-Resistant Penicillins (Anti-staphylococcal):

Cloxacillin, Dicloxacillin, Flucloxacillin (oral)
Methicillin, Nafcillin (parenteral - methicillin now historical)

3. Aminopenicillins (Extended Spectrum):

Ampicillin, Amoxicillin

4. Anti-Pseudomonal Penicillins (Extended Spectrum):

Carboxypenicillins: Carbenicillin, Ticarcillin
Ureidopenicillins: Piperacillin, Azlocillin, Mezlocillin

5. Beta-Lactamase Inhibitor Combinations:

Amoxicillin + Clavulanic acid (Co-amoxiclav)
Ampicillin + Sulbactam
Piperacillin + Tazobactam
Ticarcillin + Clavulanic acid

Mechanism of Drug Resistance to Penicillins

1. Production of Beta-Lactamases (most common): Bacteria produce enzymes (beta-lactamases/penicillinases) that hydrolyze the beta-lactam ring, rendering the drug inactive. This is the most important mechanism (e.g., S. aureus, H. influenzae, E. coli).

2. Altered Penicillin-Binding Proteins (PBPs): Mutations alter the target PBPs so penicillin cannot bind effectively. This is the mechanism in MRSA (Methicillin-Resistant S. aureus), which has an altered PBP2a encoded by the mecA gene.

3. Decreased Permeability (Porin mutations): Gram-negative bacteria can reduce outer membrane porin channels, preventing antibiotic entry into the cell (e.g., P. aeruginosa).

4. Efflux Pumps: Bacteria actively pump the antibiotic out of the cell before it can act on PBPs (e.g., P. aeruginosa).

5. Tolerance: Bacteria survive without being killed, though growth is inhibited - due to deficiency of autolytic enzymes.

Anti-Pseudomonal Penicillins

These are extended-spectrum penicillins specifically active against Pseudomonas aeruginosa (a gram-negative rod notorious for hospital-acquired infections).

Drugs:

Drug	Class	Route
Carbenicillin	Carboxypenicillin	Parenteral (oral for UTI only)
Ticarcillin	Carboxypenicillin	Parenteral
Piperacillin	Ureidopenicillin	Parenteral
Azlocillin	Ureidopenicillin	Parenteral

Mechanism of Action: Same as all penicillins - inhibit transpeptidase (PBP), blocking cross-linking of peptidoglycan cell wall, causing cell lysis.

Spectrum: Cover gram-negative rods including P. aeruginosa, Enterobacteriaceae, and Bacteroides fragilis (especially piperacillin). Also cover streptococci and enterococci.

Piperacillin is the most potent and is almost always used in combination with tazobactam (Pip-Tazo / Tazocin) for:

Hospital-acquired pneumonia
Febrile neutropenia
Complicated intra-abdominal infections
Pseudomonal bacteremia and osteomyelitis

Note: All anti-pseudomonal penicillins are susceptible to beta-lactamases; they must be combined with beta-lactamase inhibitors for clinical use.

Q3. Enumerate different groups of oral anti-diabetic drugs. Mention the mechanism of action, therapeutic uses and adverse drug reactions of Metformin. (10 marks)

Classification of Oral Anti-diabetic Drugs

1. Biguanides: Metformin

2. Sulfonylureas:

1st generation: Tolbutamide, Chlorpropamide
2nd generation: Glibenclamide (Glyburide), Glipizide, Gliclazide
3rd generation: Glimepiride

3. Meglitinides (Glinides): Repaglinide, Nateglinide

4. Thiazolidinediones (Glitazones): Pioglitazone, Rosiglitazone

5. Alpha-glucosidase Inhibitors: Acarbose, Miglitol, Voglibose

6. DPP-4 Inhibitors (Gliptins): Sitagliptin, Vildagliptin, Saxagliptin, Alogliptin

7. GLP-1 Receptor Agonists: Exenatide, Liraglutide, Dulaglutide, Semaglutide

8. SGLT-2 Inhibitors (Gliflozins): Empagliflozin, Dapagliflozin, Canagliflozin

9. Amylin Analogue: Pramlintide (injectable)

METFORMIN

Mechanism of Action: Metformin's primary mechanism is activation of AMP-activated protein kinase (AMPK) via inhibition of mitochondrial complex I in the liver. This results in:

Decreased hepatic gluconeogenesis (primary action - reduces hepatic glucose output)
Increased peripheral glucose uptake and utilization (insulin sensitizer)
Decreased intestinal glucose absorption
Improves insulin receptor sensitivity
Favorable effect on lipid profile (reduces TG and LDL)

It does NOT stimulate insulin secretion (euglycemic agent - no hypoglycemia when used alone)

Therapeutic Uses:

First-line drug for Type 2 DM (especially obese patients) - per WHO/ADA guidelines
Pre-diabetes (to delay onset of T2DM)
Polycystic Ovary Syndrome (PCOS) - improves insulin resistance, restores ovulation
Non-alcoholic fatty liver disease (NAFLD)
Prevention of T2DM in high-risk individuals

Adverse Drug Reactions:

Category	ADR
GI (most common)	Nausea, vomiting, diarrhea, metallic taste, anorexia (take with food to minimize)
Metabolic (serious, rare)	Lactic acidosis (most serious, potentially fatal; more common if renal impairment)
Nutritional	Vitamin B12 deficiency (reduces intestinal absorption; causes megaloblastic anemia)
Hypoglycemia	NOT caused by metformin alone (only with combination therapy)

Contraindications: Renal impairment (eGFR <30), hepatic failure, cardiac/respiratory failure, alcohol abuse, iodinated contrast (hold 48h before and after)

Q4. What do you mean by antimicrobial resistance? What are the strategies in pharmacotherapy that can help prevent the emergence of antimicrobial resistance? Give examples of such strategies. (10 marks)

Antimicrobial Resistance (AMR)

Definition: Antimicrobial resistance is the ability of a microorganism (bacteria, virus, fungus, or parasite) to withstand the effects of an antimicrobial agent to which it was previously susceptible. The microorganism continues to grow, multiply, and cause infection despite the presence of the drug at normally therapeutic concentrations.

Types:

Intrinsic (Natural) resistance: Inherent resistance due to structural features (e.g., gram-negative bacteria resistant to vancomycin due to outer membrane)
Acquired resistance: Develops through mutation or acquisition of resistance genes via horizontal gene transfer (conjugation, transformation, transduction)

Mechanisms of AMR:

Enzymatic inactivation (e.g., beta-lactamases)
Altered target sites (e.g., PBP2a in MRSA)
Reduced drug accumulation (decreased permeability, efflux pumps)
Metabolic bypass
Biofilm formation

Pharmacotherapy Strategies to Prevent AMR

1. Use Antibiotics Only When Necessary (Appropriate Prescribing):

Prescribe based on culture and sensitivity (C&S) results
Avoid antibiotics for viral infections (common cold, influenza)
Example: Using rapid diagnostic tests (RDTs) to confirm bacterial vs. viral infection before prescribing

2. Use the Right Drug, Right Dose, Right Duration:

Under-dosing and incomplete courses promote resistance
Example: Full 6-month course for tuberculosis; using appropriate dose of amoxicillin for strep throat rather than sub-therapeutic dosing

3. Combination Therapy:

Using two or more drugs with different mechanisms prevents emergence of resistant mutants
Example: Anti-TB therapy (HRZE - four drugs); HIV HAART; H. pylori triple therapy (PPI + Clarithromycin + Amoxicillin)

4. Antibiotic Cycling / Rotation:

Rotating antibiotics in hospitals periodically reduces selection pressure for any single antibiotic
Example: Hospitals rotating between different beta-lactams for empirical gram-negative coverage

5. Use Narrow-Spectrum Agents When Possible:

Targeted therapy after identifying the organism
Example: Using penicillin G for streptococcal infections rather than broad-spectrum amoxicillin-clavulanate

6. Beta-Lactamase Inhibitor Combinations:

Combining beta-lactams with inhibitors (clavulanate, sulbactam, tazobactam) overcomes resistance
Example: Piperacillin-Tazobactam for Pseudomonas; Amoxicillin-Clavulanate for beta-lactamase-producing H. influenzae

7. Antibiotic Stewardship Programs (ASP):

Hospital-based programs to monitor antibiotic use, guide prescribing, and restrict overuse
Example: Requiring ID physician approval for carbapenems; de-escalation policies

8. Pharmacokinetic/Pharmacodynamic Optimization:

Ensuring drug concentrations exceed MIC for sufficient time or achieving adequate AUC/MIC ratios
Example: Extended infusion of beta-lactams (time-dependent killing); once-daily high-dose aminoglycosides (concentration-dependent killing)

9. Preventing Transmission (Infection Control):

Hand hygiene, isolation precautions, and hospital hygiene reduce spread of resistant organisms
Example: Contact precautions for MRSA and VRE; alcohol-based hand rubs

10. Vaccination:

Reduces infections requiring antibiotics, thereby reducing selection pressure
Example: Pneumococcal vaccine reduces antibiotic use for pneumonia; influenza vaccine prevents secondary bacterial infections

Q5. Enumerate the drugs used for the treatment of tuberculous meningitis. Write the mechanism of action of Rifampicin and INH. (10 marks)

Drugs Used for Tuberculous Meningitis

Tuberculous meningitis (TBM) requires drugs that penetrate the blood-brain barrier (BBB) well. Treatment follows standard WHO TB guidelines but is extended.

Regimen for TBM:

Intensive phase (2 months): Isoniazid (H) + Rifampicin (R) + Pyrazinamide (Z) + Ethambutol (E)
Continuation phase (7-10 months): Isoniazid + Rifampicin (total 9-12 months, longer than pulmonary TB)

Drug	CSF Penetration	Bactericidal/Static
Isoniazid (INH)	Excellent (80-90% of serum)	Bactericidal
Rifampicin	Good (inflamed meninges)	Bactericidal
Pyrazinamide	Excellent	Bactericidal
Ethambutol	Poor (only inflamed meninges)	Bacteristatic
Streptomycin	Poor	Bactericidal

Adjunct therapy: Corticosteroids (Dexamethasone) - reduce inflammation, decrease mortality and neurological sequelae. Pyridoxine (Vit B6) given with INH to prevent peripheral neuropathy.

For drug-resistant TBM: Fluoroquinolones (Levofloxacin, Moxifloxacin) have good CSF penetration; Linezolid and Cycloserine also penetrate CSF well.

Mechanism of Action of Rifampicin

Target: Bacterial DNA-dependent RNA polymerase (DDRP)

Rifampicin binds to the beta subunit (rpoB gene) of bacterial DDRP, blocking the initiation of RNA synthesis (transcription). This prevents the formation of the first phosphodiester bond during RNA chain elongation.

Effect: Bactericidal
Acts on intracellular and extracellular organisms
Kills "persisters" - organisms intermittently metabolically active
Does NOT inhibit mammalian RNA polymerase at therapeutic concentrations
Resistance develops rapidly when used alone (single-step mutation in rpoB)

Additional actions: Rifampicin is also a potent inducer of cytochrome P450 enzymes (CYP3A4, CYP2C9), causing multiple drug interactions.

Mechanism of Action of Isoniazid (INH)

Target: Mycolic acid synthesis (unique to mycobacterial cell wall)

INH is a prodrug that must be activated by mycobacterial catalase-peroxidase (KatG enzyme). The activated form (isonicotinic acyl anion/radical) inhibits InhA (enoyl-ACP reductase) and KasA (beta-ketoacyl-ACP synthase), key enzymes in mycolic acid biosynthesis.

Mycolic acids are long-chain fatty acids essential for the integrity of the mycobacterial cell wall. Their depletion disrupts the cell wall, leading to bacterial death.

Effect: Bactericidal (on actively dividing organisms) and bacteristatic (on resting organisms)
Resistance: mutations in katG (can't activate INH), inhA overexpression, or ahpC mutations
INH inhibits pyridoxine metabolism, causing peripheral neuropathy (prevented by pyridoxine supplementation)
Metabolized by acetylation (NAT2 gene) - slow vs. fast acetylators affect toxicity and efficacy

Q6. Enumerate the drugs used for the treatment of multi-bacillary leprosy. Write the advantages of multidrug therapy in leprosy. How would you treat Lepra-1 reactions? (10 marks)

Drugs Used for Multi-Bacillary (MB) Leprosy

Multi-bacillary leprosy includes lepromatous leprosy (LL), borderline lepromatous (BL), and mid-borderline (BB) types (BIs > 2+).

WHO Recommended MDT Regimen for MB Leprosy (12 months):

Drug	Dose	Frequency
Rifampicin	600 mg	Once monthly (supervised)
Clofazimine	300 mg monthly (supervised) + 50 mg daily (self-administered)	Monthly + Daily
Dapsone	100 mg	Daily (self-administered)

Duration: 12 months

Other drugs used in leprosy (especially drug-resistant or MDT-intolerant):

Fluoroquinolones: Ofloxacin, Moxifloxacin
Minocycline
Clarithromycin
Thalidomide (for ENL/Type 2 reactions)

Advantages of Multidrug Therapy (MDT) in Leprosy

Prevents drug resistance: Monotherapy (especially dapsone alone) led to widespread dapsone resistance. MDT attacks multiple targets simultaneously, preventing emergence of resistant mutants.
Shortens treatment duration: MDT has reduced treatment from many years to 6-12 months, improving patient compliance.
Bactericidal action: Rifampicin is rapidly bactericidal - kills >99.9% of viable M. leprae within days, making patients non-infectious quickly.
Reduces relapse rates: Relapses are extremely rare with properly completed MDT (<1% in MB leprosy).
Addresses multiple metabolic targets: Each drug in the regimen has a different mechanism - rifampicin (RNA polymerase), dapsone (folate synthesis), clofazimine (DNA binding + reactive oxygen species).
Overcomes pre-existing resistance: If the organism is already resistant to one drug, the other two drugs in the regimen remain effective.
Free provision by WHO: MDT is provided free of charge globally, improving access and adherence.
Cost-effective and operationally feasible: Simple regimen administered at health posts reduces the burden on tertiary care.

Treatment of Lepra Type 1 (Reversal) Reactions

Lepra Type 1 (Reversal Reaction) is a delayed hypersensitivity (Type IV/cell-mediated) reaction that occurs in borderline leprosy (BT, BB, BL). It involves sudden upgrading of cell-mediated immunity and is characterized by erythema and edema of existing skin lesions, and acute neuritis (nerve involvement is the most important feature - can cause permanent disability).

Management:

1. Continue MDT: MDT should NOT be stopped. It must be continued throughout the reaction.

2. Corticosteroids - Drug of Choice:

Prednisolone is the mainstay treatment
Starting dose: 40-60 mg/day orally
Gradually tapered over 3-6 months (minimum 12 weeks for neural involvement)
Prevents permanent nerve damage
Indication: Any neuritis, nerve function impairment, or facial patches

3. Supportive measures:

Splinting and rest of affected limbs
Physiotherapy to prevent contractures
Eye care (patching if lagophthalmos present)
Analgesics for pain

4. Clofazimine (150-300 mg/day) has mild anti-inflammatory properties and can be used as a steroid-sparing agent in prolonged reactions.

Note: Type 1 reactions are NOT treated with thalidomide (thalidomide is used for Type 2/ENL reactions). Azathioprine or cyclosporine can be used as steroid-sparing agents if prolonged corticosteroid use is needed.

FA Structured Long Questions - BATCH B (02/06/2026)

Q1. Classify oral anti-diabetic drugs. Describe briefly mechanism of action, adverse effects, advantages & disadvantages of Sitagliptin. (10 marks)

Classification of Oral Anti-diabetic Drugs

(Same as Batch A Q3 classification - see above)

1. Biguanides: Metformin 2. Sulfonylureas: Glibenclamide, Glipizide, Glimepiride, Gliclazide 3. Meglitinides: Repaglinide, Nateglinide 4. Thiazolidinediones: Pioglitazone, Rosiglitazone 5. Alpha-glucosidase Inhibitors: Acarbose, Voglibose, Miglitol 6. DPP-4 Inhibitors (Gliptins): Sitagliptin, Vildagliptin, Saxagliptin, Linagliptin, Alogliptin 7. GLP-1 Receptor Agonists: Exenatide, Liraglutide, Semaglutide 8. SGLT-2 Inhibitors: Empagliflozin, Dapagliflozin, Canagliflozin

SITAGLIPTIN (DPP-4 Inhibitor / "Gliptin")

Mechanism of Action:

The incretin hormones GLP-1 (Glucagon-Like Peptide-1) and GIP (Glucose-dependent Insulinotropic Polypeptide) are released from the gut after meals. They stimulate insulin secretion and suppress glucagon in a glucose-dependent manner. However, these hormones are rapidly degraded by the enzyme Dipeptidyl Peptidase-4 (DPP-4) within minutes.

Sitagliptin inhibits DPP-4, thereby preventing the breakdown of endogenous GLP-1 and GIP. This increases their concentration approximately 2-3 fold, resulting in:

Enhanced glucose-dependent insulin secretion from beta cells
Suppression of glucagon from alpha cells (postprandial)
Net effect: Lowering of blood glucose in a glucose-dependent manner (only when glucose is elevated - hence minimal hypoglycemia risk)

Adverse Effects:

System	ADR
Upper respiratory	Nasopharyngitis, sinusitis (class effect)
GI	Nausea, diarrhea (mild)
Urinary	UTI (increased risk)
Musculoskeletal	Arthralgia (joint pain) - FDA warning
Skin	Urticaria, angioedema (rare, hypersensitivity)
Pancreas	Pancreatitis (rare but reported - controversial)
Other	Headache

Hypoglycemia: rare (only in combination with sulfonylurea/insulin)

Advantages of Sitagliptin:

Glucose-dependent action - Very low risk of hypoglycemia when used as monotherapy
Weight neutral - Does not cause weight gain (unlike sulfonylureas or insulin)
Once-daily oral dosing (100 mg OD) - improves adherence
Well-tolerated - minimal GI side effects compared to metformin
Can be used in combination with metformin, sulfonylureas, or insulin
Modest benefit in preserving beta-cell function
Safe in elderly patients
Available as fixed-dose combination (Sitagliptin + Metformin = Janumet)

Disadvantages of Sitagliptin:

Modest HbA1c reduction (~0.5-0.8% reduction) - less effective than metformin or sulfonylureas
Expensive - cost is a significant barrier
Dose adjustment required in renal impairment (50 mg for eGFR 30-50; 25 mg for eGFR <30)
Nasopharyngitis and upper respiratory infections (class side effect)
Rare but serious risk of pancreatitis
No cardiovascular benefit shown (unlike SGLT-2 inhibitors or GLP-1 agonists)
No weight reduction benefit (unlike GLP-1 agonists)
Long-term safety data still accumulating

Q2. Classify aminoglycosides. Describe their mechanism of action. Mention their important therapeutic uses and adverse effects. (10 marks)

Classification of Aminoglycosides

Natural Aminoglycosides:

Streptomycin (first aminoglycoside - from S. griseus)
Neomycin
Kanamycin
Tobramycin
Gentamicin (from Micromonospora - hence "micin" spelling)
Spectinomycin (structurally related)

Semi-synthetic Aminoglycosides:

Amikacin (derived from kanamycin - broadest spectrum, most resistant to inactivating enzymes)
Netilmicin (derived from sisomicin)
Dibekacin

Classification by Spectrum:

Narrow spectrum (mainly gram-positive): Streptomycin, Neomycin
Broader gram-negative spectrum: Gentamicin, Tobramycin, Amikacin, Netilmicin

Mechanism of Action

Aminoglycosides are concentration-dependent, bactericidal antibiotics that act on bacterial ribosomes:

Step 1 - Entry: The drug enters the bacterial cell through an oxygen-dependent active transport mechanism (hence inactive against strict anaerobes).

Step 2 - Ribosomal binding: Aminoglycosides bind irreversibly to the 30S ribosomal subunit (specifically the 16S rRNA component).

Step 3 - Misreading of mRNA: This binding causes:

Misreading of the mRNA codon
Incorporation of wrong amino acids into the growing polypeptide chain
Production of aberrant (nonsense) proteins

Step 4 - Membrane disruption: These faulty proteins insert into the bacterial cell membrane, causing increased membrane permeability. More aminoglycoside enters the cell (a self-amplifying cycle), leading to rapid cell death.

Key features:

Bactericidal (even at low concentrations)
Concentration-dependent killing (higher peak concentrations = more killing)
Post-antibiotic effect (PAE) - bacterial killing continues even after drug concentrations fall below MIC
Synergistic with beta-lactams (which disrupt cell wall, enhancing aminoglycoside entry)

Therapeutic Uses

Drug	Primary Use
Gentamicin	Gram-negative sepsis, UTI, endocarditis (synergy with penicillin for enterococcal/streptococcal endocarditis)
Amikacin	Serious gram-negative infections, drug-resistant TB (reserve drug)
Tobramycin	Pseudomonas aeruginosa infections (especially in CF patients - inhaled form), eye infections
Streptomycin	First-line for TB (HRZE regimen), plague, tularemia, brucellosis
Neomycin	Topical (skin, eye, ear infections); pre-operative bowel preparation; hepatic encephalopathy (reduces gut ammonia-producing bacteria)
Spectinomycin	Gonorrhea (penicillin-resistant strains)

Clinical uses of aminoglycosides in general:

Serious gram-negative bacillary infections (hospital-acquired pneumonia, septicemia)
UTIs caused by resistant organisms
Infective endocarditis (combination therapy)
Tuberculosis (streptomycin as 2nd-line)
Biliary tract infections
Meningitis (gram-negative, in combination)

Adverse Effects

1. Ototoxicity (most important):

Vestibulotoxicity: Dizziness, vertigo, nystagmus, ataxia (especially with streptomycin and gentamicin)
Cochleotoxicity/Auditory toxicity: Tinnitus, high-frequency hearing loss progressing to deafness (especially amikacin and neomycin)
Mechanism: Destruction of hair cells in cochlea/vestibular apparatus
Risk factors: High doses, prolonged use, renal failure, prior ear disease, concurrent loop diuretics
Irreversible

2. Nephrotoxicity (dose-dependent, usually reversible):

Accumulation in proximal tubular cells - causes tubular necrosis
Manifests as rising serum creatinine, reduced GFR
Risk factors: Prolonged use, elderly, pre-existing renal disease, concurrent NSAIDs or vancomycin
Monitoring: Regular serum creatinine and drug levels required

3. Neuromuscular Blockade (rare, serious):

Aminoglycosides inhibit presynaptic release of acetylcholine and block postsynaptic receptors
Can cause respiratory muscle paralysis, especially after rapid IV injection
Risk increased with concurrent curare-type muscle relaxants or in myasthenia gravis
Treatment: Calcium gluconate or neostigmine

4. Other:

Hypersensitivity reactions (rash, fever) - rare
Peripheral neuropathy (streptomycin)
Local irritation at injection site

Monitoring: Therapeutic drug monitoring (TDM) - measure peak and trough levels, renal function tests, audiometry for prolonged use.

Q3. Classify antitubercular drugs. How will you manage the patient of newly diagnosed pulmonary tuberculosis? Describe important adverse effects of first-line antitubercular drugs. (10 marks)

Classification of Antitubercular Drugs

A. First-Line Drugs (HRZE):

H - Isoniazid (INH)
R - Rifampicin
Z - Pyrazinamide
E - Ethambutol
S - Streptomycin (also considered first-line by some)

B. Second-Line Drugs:

Fluoroquinolones: Levofloxacin, Moxifloxacin, Ofloxacin
Injectable agents: Amikacin, Kanamycin, Capreomycin
Oral bacteriostatic: Ethionamide, Prothionamide, Cycloserine, Para-aminosalicylic acid (PAS)

C. Third-Line / New Drugs (MDR-TB):

Bedaquiline (ATP synthase inhibitor)
Delamanid (mycolic acid synthesis inhibitor)
Linezolid
Clofazimine

Management of Newly Diagnosed Pulmonary Tuberculosis

(New Smear-Positive / New Bacteriologically Confirmed PTB)

WHO Short-Course Chemotherapy Regimen:

Intensive Phase (2 months):

2HRZE - Isoniazid + Rifampicin + Pyrazinamide + Ethambutol (daily for 2 months)

Continuation Phase (4 months):

4HR - Isoniazid + Rifampicin (daily for 4 months)

Total duration: 6 months

Drug Doses:

Drug	Daily Dose (adult)
Isoniazid (H)	5 mg/kg (max 300 mg)
Rifampicin (R)	10 mg/kg (max 600 mg)
Pyrazinamide (Z)	25 mg/kg (max 2 g)
Ethambutol (E)	15 mg/kg (max 1.2 g)

Additional measures:

Pyridoxine (Vit B6) 25 mg/day with INH (prevents peripheral neuropathy)
DOTS (Directly Observed Treatment, Short-course) to ensure compliance
Baseline LFTs, visual acuity, uric acid
Test for HIV; if positive, start ART (after initial 2-8 weeks of ATT)
Sputum smear microscopy at 2, 5, 6 months to monitor response
Nutritional support, infection control (isolation if needed initially)
Notifiable disease - report to public health authorities

Important Adverse Effects of First-Line ATT Drugs

Drug	Major Adverse Effects
Isoniazid	Peripheral neuropathy (prevented by pyridoxine), hepatotoxicity, drug-induced lupus (SLE-like), psychosis, seizures, sideroblastic anemia, gynecomastia
Rifampicin	Hepatotoxicity, orange-red discoloration of body fluids (urine, tears, sputum - harmless but warn patients), GI upset, flu-like syndrome (intermittent therapy), thrombocytopenia, CYP450 induction (multiple drug interactions - reduces efficacy of OCP, anticoagulants, antiretrovirals)
Pyrazinamide	Hepatotoxicity (most hepatotoxic first-line drug), hyperuricemia/gout (inhibits uric acid excretion), arthralgia, fever, flushing, photosensitivity
Ethambutol	Retrobulbar neuritis (optic neuritis) - reduced visual acuity, loss of red-green color discrimination - dose-dependent and potentially irreversible if not stopped; baseline visual acuity testing mandatory
Streptomycin	Ototoxicity (vestibular more than cochlear), nephrotoxicity, neuromuscular blockade

Hepatotoxicity: All of H, R, and Z are hepatotoxic. Stop all drugs if transaminases >5x ULN or clinical jaundice. Reinstate drugs one by one after recovery (R first, then H, then Z).

Q4. Classify drugs used in hyperthyroidism. Describe mechanism of action and adverse effects of thioamides. Which antithyroid drug should be used during pregnancy and why? (10 marks)

Classification of Drugs Used in Hyperthyroidism

1. Thioamides (Antithyroid drugs):

Propylthiouracil (PTU)
Carbimazole
Methimazole (active metabolite of carbimazole)

2. Ionic Inhibitors (Anion Inhibitors):

Potassium Perchlorate
Potassium Thiocyanate (Block iodide uptake by competing with iodide for transport)

3. High Dose Iodine (Wolff-Chaikoff effect):

Lugol's iodine (potassium iodide + iodine)
Potassium iodide
Uses: Pre-operative preparation, thyroid storm

4. Radioactive Iodine:

Iodine-131 (¹³¹I)
Destroys thyroid tissue by beta radiation
Used for: Graves' disease (definitive treatment), toxic nodular goiter

5. Beta-Adrenergic Blockers (Adjunct therapy):

Propranolol (also inhibits peripheral T4 to T3 conversion)
Atenolol, Metoprolol
Control symptoms (palpitations, tremor, anxiety, sweating) but do not reduce thyroid hormone synthesis

6. Calcium Channel Blockers:

Diltiazem (if beta-blockers contraindicated)

7. Surgical:

Subtotal/total thyroidectomy (not a drug but part of management)

Thioamides - Mechanism of Action

Thioamides (PTU, Carbimazole/Methimazole) work by multiple mechanisms:

Primary Mechanism:

Inhibit thyroid peroxidase (TPO) enzyme, which is required for:
1. Oxidation of iodide (I⁻) to iodine (I₀/I₂)
2. Organification - iodination of tyrosine residues on thyroglobulin to form MIT and DIT
3. Coupling - coupling of MIT + DIT to form T3 and T4

Additional Mechanism of PTU only:

Inhibits peripheral conversion of T4 to T3 (active form) by inhibiting the enzyme deiodinase (5'-deiodinase) in peripheral tissues - makes PTU preferable in thyroid storm

Onset of action: Clinical effect is delayed (1-3 weeks) because existing stored thyroid hormones must be depleted before effects are seen.

Immunosuppressive effect: In Graves' disease, thioamides also reduce TSH receptor antibody levels (anti-TSHR), contributing to remission.

Adverse Effects of Thioamides

ADR	Details
Agranulocytosis	Most serious (0.1-0.5%); abrupt onset - patient must report sore throat/fever immediately; require urgent WBC; stop drug if confirmed
Mild leukopenia	Common, usually self-limiting
Skin rashes	Maculopapular rash, pruritus (5-10%)
Hepatotoxicity	PTU more hepatotoxic (fulminant hepatic failure possible); carbimazole causes cholestatic jaundice
GI	Nausea, vomiting, taste disturbance
Arthralgia	Joint pain, lupus-like syndrome
Hypothyroidism	If dose too high or prolonged - monitor TFTs
Vasculitis	PTU-associated ANCA-positive vasculitis
Goiter	Compensatory TSH rise with prolonged use can enlarge thyroid
Teratogenicity	Carbimazole/methimazole - aplasia cutis, choanal atresia (rare) in first trimester

Antithyroid Drug in Pregnancy

First trimester: Propylthiouracil (PTU) is preferred

Second and third trimester: Carbimazole / Methimazole is preferred (or continue PTU if controlled)

Rationale:

PTU in first trimester:

Carbimazole/methimazole are associated with rare but serious teratogenic effects in the first trimester: aplasia cutis (scalp skin defect), choanal atresia, esophageal atresia, and methimazole embryopathy (facial dysmorphism). PTU does not carry these teratogenic risks.
Therefore, PTU is the drug of choice in the first trimester.

Carbimazole/Methimazole in 2nd-3rd trimester:

PTU carries risk of maternal hepatotoxicity (fulminant hepatic failure) with prolonged use.
After the critical organogenesis period (first trimester), carbimazole is switched to because it is safer for the mother long-term.
Both drugs cross the placenta and can cause fetal hypothyroidism and goiter - use the minimum effective dose.

Other considerations in pregnancy:

Target TSH: 0.1-2.5 mIU/L in first trimester
Breastfeeding: PTU preferred (less transfer to breast milk than carbimazole); both are compatible with breastfeeding at low doses.
Radioactive iodine is absolutely contraindicated in pregnancy (destroys fetal thyroid)
Beta-blockers (propranolol) can be used for symptomatic control; avoid prolonged use (IUGR risk)

Q5. Describe briefly the pathophysiology of bronchial asthma. Classify the drugs used in bronchial asthma. Explain the rationale for the use of Salmeterol and Fluticasone in the treatment of chronic asthma. (10 marks)

Pathophysiology of Bronchial Asthma

Bronchial asthma is a chronic inflammatory disorder of the airways characterized by reversible airflow obstruction, bronchial hyperresponsiveness, and airway remodeling.

Key pathophysiological mechanisms:

1. Sensitization Phase: Allergen exposure causes dendritic cells to present antigens to T-helper (Th2) lymphocytes. Th2 cells release cytokines (IL-4, IL-5, IL-13) that promote IgE production by B cells and eosinophil recruitment.

2. Early Phase Response (Immediate, 0-30 min): On re-exposure to allergen, it cross-links IgE on mast cells, triggering mast cell degranulation with release of:

Histamine (bronchospasm, mucosal edema)
Leukotrienes (LTC4, LTD4, LTE4) - potent bronchoconstrictors
Prostaglandins (PGD2)
Platelet Activating Factor (PAF)
Tryptase

3. Late Phase Response (4-12 hours): Inflammatory cell infiltration (eosinophils, neutrophils, Th2 cells) leads to:

Eosinophilic inflammation - major basic protein (MBP) damages epithelium
Goblet cell hyperplasia - increased mucus production
Smooth muscle hypertrophy/hyperplasia
Subepithelial fibrosis (remodeling)

4. Neurogenic Mechanisms:

Reduced beta-2 adrenergic responsiveness
Vagal hyperactivity (cholinergic bronchoconstriction)
Airway irritant receptors hypersensitized - triggers bronchospasm to non-specific stimuli (exercise, cold air, pollutants)

Net Result: Airway narrowing due to:

Bronchospasm
Mucosal edema
Increased mucus secretion
Airway remodeling (structural changes - irreversible component)

Classification of Drugs Used in Bronchial Asthma

A. Bronchodilators:

Beta-2 Adrenergic Agonists:

Short-acting (SABA): Salbutamol, Terbutaline (reliever - used PRN)
Long-acting (LABA): Salmeterol, Formoterol (controller - used with ICS)

Anticholinergics:

Short-acting (SAMA): Ipratropium bromide
Long-acting (LAMA): Tiotropium (mainly COPD, adjunct in severe asthma)

Methylxanthines: Theophylline, Aminophylline

B. Anti-inflammatory Drugs (Controllers):

Inhaled Corticosteroids (ICS) - mainstay of maintenance:

Fluticasone, Budesonide, Beclomethasone, Ciclesonide

Systemic Corticosteroids: Prednisolone, Hydrocortisone (acute severe asthma)
Leukotriene Antagonists (LTRAs): Montelukast, Zafirlukast
Mast Cell Stabilizers: Sodium cromoglycate, Nedocromil (mainly prophylactic)
Anti-IgE: Omalizumab (biologic - severe allergic asthma)
Anti-IL-5: Mepolizumab, Reslizumab, Benralizumab (for eosinophilic asthma)

C. Combination preparations:

Salmeterol + Fluticasone (Seretide/Advair)
Formoterol + Budesonide (Symbicort)

Rationale for Use of Salmeterol + Fluticasone in Chronic Asthma

Salmeterol (LABA) alone: Salmeterol activates beta-2 adrenergic receptors on bronchial smooth muscle, activating adenylyl cyclase -> increased cAMP -> protein kinase A activation -> smooth muscle relaxation -> bronchodilation. Duration: 12 hours. Reduces bronchospasm and night-time symptoms.

HOWEVER - Salmeterol should NEVER be used as monotherapy in asthma due to the risk of severe asthma attacks and death if used without ICS (masks symptoms without treating underlying inflammation - FDA Black Box Warning).

Fluticasone (ICS) alone: Corticosteroids bind to intracellular glucocorticoid receptors, translocate to nucleus, and:

Suppress transcription of pro-inflammatory genes (IL-4, IL-5, IL-13, TNF-alpha)
Induce anti-inflammatory proteins (lipocortin-1 - inhibits phospholipase A2)
Reduce eosinophil survival and airway inflammation
Decrease mucus hypersecretion and airway edema
Upregulate beta-2 receptor expression (synergism with LABA)

Rationale for Combination (Salmeterol + Fluticasone):

The combination addresses BOTH key components of asthma pathophysiology:

Fluticasone attacks the underlying inflammation (the root cause)
Salmeterol provides sustained bronchodilation (symptom control)

Synergistic mechanisms:

Fluticasone upregulates beta-2 receptors, making salmeterol more effective
Salmeterol activates GRs (glucocorticoid receptors) via nuclear translocation, enhancing fluticasone's anti-inflammatory action
Together they reduce exacerbations more than either alone (shown in SMART trial and multiple RCTs)

Clinical benefits of combination:

Better symptom control and lung function than either drug alone
Reduction in exacerbation frequency
Allows lower doses of ICS (steroid-sparing)
Once or twice daily dosing improves compliance
Indicated in Step 3-4 of GINA guidelines (moderate-severe persistent asthma)

Q6. Describe briefly the pathophysiology of vomiting. Classify antiemetic drugs. Compare and contrast metoclopramide and domperidone. (10 marks)

Pathophysiology of Vomiting

Vomiting (emesis) is a coordinated reflex that expels gastric contents through the mouth. It is controlled by the vomiting center (VC) in the lateral reticular formation of the medulla oblongata.

Key control centers:

1. Vomiting Center (VC):

Located in medulla oblongata
The final common pathway - receives inputs from multiple sources
Sends motor commands via vagus, phrenic, and spinal nerves to effector organs
Rich in muscarinic (M1), histaminic (H1), and NK1 receptors

2. Chemoreceptor Trigger Zone (CTZ):

Located in the area postrema on the floor of the 4th ventricle
Outside the blood-brain barrier (BBB) - can be stimulated by blood-borne emetic agents
Rich in Dopamine (D2), 5-HT3 (serotonin), NK1 receptors
Stimulated by: drugs (opioids, digoxin, cytotoxics), toxins, metabolic disorders (uremia, DKA), radiation

3. Vestibular System:

Activated by motion - signals via vestibulocochlear nerve to cerebellum, then to VC
Rich in H1 and M1 receptors

4. GI Tract (Peripheral inputs):

Gut wall contains 5-HT3 receptors on vagal afferent nerve endings
Distension, irritants, cytotoxic drugs, radiation stimulate serotonin release from enterochromaffin cells -> activates vagal afferents -> VC
Vagus nerve (via D2 and 5-HT4 receptors) also provides afferent input

5. Higher Cortical Centers:

Anticipatory nausea, visual/olfactory stimuli, emotional distress -> limbic system -> VC

Sequence of vomiting act: Nausea (awareness) -> Retching (coordinated contraction of diaphragm and abdominal muscles with closed pylorus) -> Vomiting (retroperistalsis + relaxation of LES + glottis closure to protect airway + forceful expulsion)

Classification of Antiemetic Drugs

1. Dopamine (D2) Receptor Antagonists:

Phenothiazines: Prochlorperazine, Chlorpromazine, Promethazine
Butyrophenones: Haloperidol, Droperidol
Substituted benzamides: Metoclopramide, Domperidone

2. 5-HT3 Receptor Antagonists (Setrons) - highly effective for chemotherapy-induced:

Ondansetron, Granisetron, Tropisetron, Palonosetron

3. H1 Antihistamines (for motion sickness, vestibular):

Dimenhydrinate, Cinnarizine, Meclizine, Promethazine

4. Anticholinergics (for motion sickness):

Hyoscine (Scopolamine) - transdermal patch

5. NK1 Receptor Antagonists (for CINV - delayed phase):

Aprepitant, Fosaprepitant, Netupitant

6. Corticosteroids (adjunct in CINV):

Dexamethasone

7. Cannabinoids:

Nabilone, Dronabinol (CINV - refractory)

8. Prokinetics:

Metoclopramide (also D2 antagonist + 5-HT4 agonist)
Domperidone
Erythromycin (motilin receptor agonist)

9. Others:

Ginger (P6 acupressure, herbal)
Pyridoxine (vitamin B6 - pregnancy nausea)

Comparison of Metoclopramide vs. Domperidone

Feature	Metoclopramide	Domperidone
Drug class	Substituted benzamide (D2 antagonist + 5-HT4 agonist + 5-HT3 antagonist at high doses)	Substituted benzamide (D2 antagonist)
BBB penetration	YES - penetrates BBB	NO - does NOT penetrate BBB (peripherally acting)
Site of action	CTZ + peripheral GI + CNS	CTZ + peripheral GI only
Mechanism	Blocks D2 receptors in CTZ and gut; 5-HT4 agonism enhances gut motility	Blocks D2 receptors in CTZ and peripheral gut; does not cross BBB
Prokinetic effect	Yes - enhances gastric emptying, increases LES tone, increases intestinal motility	Yes - similar prokinetic effect
CNS effects	YES - sedation, anxiety, depression	Minimal (does not cross BBB)
Extrapyramidal side effects (EPS)	Common - akathisia, dystonia, tardive dyskinesia (especially young patients and elderly)	Rare/absent (due to poor BBB penetration)
Hyperprolactinemia	Yes - galactorrhea, amenorrhea, gynecomastia	Yes - also causes (acts on pituitary, which is outside BBB)
Cardiac effects	QT prolongation (high doses)	QT prolongation (significant concern; may trigger arrhythmias - FDA/EMA warnings)
Drug interactions	Multiple CNS drug interactions	Interactions with CYP3A4 inhibitors (ketoconazole, macrolides) increase cardiac risk
Route	Oral, IM, IV	Oral, suppository
Indications	CINV, PONV, diabetic gastroparesis, GERD, nasogastric tube placement	Nausea/vomiting (non-CINV), gastroparesis, GERD
Use in CINV	Effective (especially high-dose IV for cisplatin)	Less effective for severe CINV
Preferred in	Hospital/inpatient, CINV, when IV route needed	Outpatient functional nausea, less EPS risk needed
Pregnancy	Considered relatively safe (category B)	Avoid - limited data
Lactation	Promotes lactation (prolactin elevation) - used off-label for this	Also promotes lactation
Elderly patients	Use with CAUTION - higher EPS and sedation risk	Preferred over metoclopramide due to lower EPS risk

Summary of key contrast: The main clinical difference is that metoclopramide crosses the BBB while domperidone does not. This makes domperidone safer from a neurological standpoint (less EPS, less sedation) but domperidone carries a higher cardiac risk (QT prolongation) and is not available for IV use. Metoclopramide is more effective for severe nausea (CINV) but requires careful monitoring for EPS, particularly in young adults and the elderly.

All answers are based on standard pharmacology references (Katzung, Tripathi, Goodman & Gilman, WHO guidelines). These are exam-style structured answers suitable for 10-mark questions.

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