A 25-year-old man has continuous low-grade fever for past 7 days. He also complaints of abdominal pain, loss of appetite, tiredness, and loose motions. On examination he was febrile, and he had coated tongue. Total leucocyte count was found to be elevated. Blood Widal test was positive and blood culture was positive for S.Typhi. a. What are the drugs given in this condition? b. Which is the drug empirically used in this condition? Explain its mechanism of action, adverse effects and other uses of this drug? c. Mention the uses and adverse effects of fluroquinolones.
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I now have all the key information from the library. Here is the complete, detailed answer:
Diagnosis: Enteric Fever (Typhoid Fever) due to Salmonella Typhi
The clinical picture - continuous low-grade fever for 7 days, abdominal pain, anorexia, malaise, loose stools, coated tongue, leukocytosis, positive Widal test and positive blood culture for S. Typhi - is classic for typhoid fever.
(a) Drugs Used in Typhoid Fever
Treatment depends on drug susceptibility. According to current guidelines (Park's Textbook of Preventive and Social Medicine):
| Susceptibility | Optimal Therapy | Dose (mg/kg/day) | Duration | Alternatives |
|---|---|---|---|---|
| Fully sensitive | Fluoroquinolone (ciprofloxacin/ofloxacin) | 15 | 5-7 days | Chloramphenicol (50-75), Amoxicillin (75-100), TMP-SMX (8-40) - each for 14 days |
| Multidrug resistant (MDR) | Fluoroquinolone or Cefixime | 15 / 15-20 | 5-7 / 7-14 days | Azithromycin, Cefixime |
| Quinolone resistant | Azithromycin or Ceftriaxone | 8-10 / 75 | 7 / 10-14 days | Cefixime |
In summary, the main drugs used are:
- Fluoroquinolones - ciprofloxacin, ofloxacin (first-line for fully sensitive strains)
- Ceftriaxone / Cefixime (third-generation cephalosporins) - for MDR or quinolone-resistant strains
- Azithromycin - increasingly used, especially in areas with quinolone resistance
- Chloramphenicol - older first-line drug, now reserved for susceptible strains
- Amoxicillin / Ampicillin - alternatives for sensitive strains
- Co-trimoxazole (TMP-SMX) - alternative for sensitive strains
(b) Drug Used Empirically - Ciprofloxacin (Fluoroquinolone)
Ciprofloxacin is the drug of choice used empirically in typhoid fever in areas where quinolone-resistant strains are not prevalent. Where quinolone resistance is common (e.g., parts of South Asia), azithromycin or ceftriaxone is preferred empirically.
Mechanism of Action
Fluoroquinolones inhibit two bacterial enzymes critical for DNA synthesis:
- DNA gyrase (topoisomerase II) - mainly in gram-negative bacteria. This enzyme introduces negative supercoils into DNA, which is essential for DNA replication and transcription. Inhibition causes DNA strand breaks and bacterial cell death.
- Topoisomerase IV - mainly targeted in gram-positive bacteria. This enzyme is responsible for decatenation (separation) of newly replicated circular daughter chromosomes. Inhibition prevents chromosome segregation.
The result is bactericidal activity - the drug is concentration-dependent (efficacy depends on peak concentration / MIC ratio, i.e., Cmax:MIC). Fluoroquinolones also have a post-antibiotic effect (bacterial killing continues even after drug levels fall below MIC).
- Katzung's Basic and Clinical Pharmacology, 16th Edition; Goodman & Gilman
Adverse Effects of Ciprofloxacin / Fluoroquinolones
Gastrointestinal (most common):
- Nausea, vomiting, abdominal discomfort, diarrhea
CNS:
- Headache, dizziness/vertigo
- Delirium, hallucinations, toxic psychosis (especially in elderly)
- Seizures (particularly with NSAIDs co-administration which lowers seizure threshold)
Musculoskeletal (class-specific warning):
- Arthralgia, myalgia, polyarthritis
- Tendonitis and tendon rupture - Achilles tendon most commonly affected; risk increases with age, corticosteroid use, and renal impairment
- Contraindicated in children under 15 years due to potential damage to developing cartilage and joints (chondrotoxicity shown in animal studies)
- Avoid in pregnancy for the same reason (cartilage/joint toxicity to fetus)
Cardiac:
- QT interval prolongation on ECG, potentially leading to ventricular arrhythmias (torsades de pointes) - more common with levofloxacin and moxifloxacin
Renal:
- Crystalluria, nephrolithiasis
- Acute interstitial nephritis, microscopic/gross hematuria (especially with ciprofloxacin)
Hepatic:
- Hepatitis, acute liver failure (rare but reported)
Dermatological:
- Rash, photosensitivity (patients should avoid excessive sun exposure)
Drug interactions:
- Antacids (Mg2+, Al3+, Ca2+), sucralfate, zinc, iron - chelate fluoroquinolones and reduce oral absorption; should be given 2 hours apart
- Prolongs half-life of theophylline and warfarin (inhibits CYP1A2)
- The Essentials of Forensic Medicine and Toxicology 36th ed; Katzung's Basic and Clinical Pharmacology
Other Uses of Fluoroquinolones (Ciprofloxacin)
Fluoroquinolones have broad-spectrum activity and are used in many infections:
- Urinary tract infections (UTIs) - complicated UTIs and pyelonephritis
- Typhoid fever and non-typhoidal salmonellosis
- Gastrointestinal infections - traveller's diarrhoea, Shigellosis, Campylobacter
- Respiratory tract infections - community-acquired pneumonia, Legionella pneumonia (levofloxacin, moxifloxacin); exacerbations of chronic bronchitis
- Gonorrhoea (though resistance is now widespread)
- Anthrax (Bacillus anthracis) - ciprofloxacin is a first-line drug
- Bone and joint infections (excellent bone penetration)
- Prostatitis - excellent penetration into prostatic tissue
- Meningitis - due to gram-negative organisms (penetrates CSF)
- Tuberculosis - later-generation fluoroquinolones (levofloxacin, moxifloxacin) are used in MDR-TB regimens
- Ophthalmic infections - topical fluoroquinolones for bacterial conjunctivitis, corneal ulcers
- Intra-abdominal infections (in combination)
- Skin and soft tissue infections caused by gram-negative organisms
- Katzung's Basic and Clinical Pharmacology, 16th Edition
(c) Uses and Adverse Effects of Fluoroquinolones (Summary)
Uses (see detailed list above)
Key clinical areas:
- Enteric infections: typhoid, Shigellosis, traveller's diarrhoea
- Urinary infections: UTI, pyelonephritis, prostatitis
- Respiratory infections: pneumonia (esp. atypicals), bronchitis
- STDs: gonorrhoea (where sensitive)
- Bone/joint: osteomyelitis, septic arthritis
- Anthrax, plague, tularaemia (bioterrorism agents)
- MDR-TB (levofloxacin, moxifloxacin)
- Ophthalmic (topical)
Adverse Effects Summary
| System | Effect |
|---|---|
| GI | Nausea, vomiting, diarrhoea, abdominal pain |
| CNS | Headache, dizziness, insomnia, seizures, delirium |
| Musculoskeletal | Tendinitis, tendon rupture, arthralgia, myalgia |
| Cardiac | QT prolongation, arrhythmias |
| Renal | Crystalluria, nephritis, haematuria |
| Hepatic | Hepatitis, liver failure (rare) |
| Skin | Rash, photosensitivity |
| Special populations | Avoid in children <15 years (cartilage damage); Avoid in pregnancy |
Sources: Park's Textbook of Preventive and Social Medicine; Katzung's Basic and Clinical Pharmacology, 16th Edition; The Essentials of Forensic Medicine and Toxicology 36th ed.
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