NSAIDs are best avoided in:

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: B

Rationale: Ciprofloxacin (B) is the correct answer as it's widely recommended for prophylaxis in close adult contacts of meningococcal disease caused by Neisseria meningitidis. A single dose effectively reduces nasopharyngeal carriage, preventing invasive disease spread. Co-amoxiclav (A) is appropriate for human and animal bites due to its coverage of anaerobes and skin pathogens like Pasteurella, but B is highlighted here. Flucloxacillin (C) isn't used for diphtheria prophylaxis; erythromycin or penicillin is preferred to eradicate Corynebacterium diphtheriae carriage. Erythromycin (D) is suitable for pertussis prophylaxis in unvaccinated infants exposed to Bordetella pertussis, reducing transmission. Aciclovir (original E) isn't standard for herpes labialis contact prophylaxis. Ciprofloxacin's efficacy, ease of administration, and alignment with public health protocols make it a critical tool in controlling meningococcal outbreaks.

Correct Answer: A

Rationale: Clarithromycin is effective against Mycoplasma pneumoniae (A), a common cause of atypical pneumonia, due to its enhanced activity over erythromycin against intracellular pathogens. It's also used in Legionnaire's disease (B), caused by Legionella pneumophila, often as an alternative to azithromycin. It treats Campylobacter enteritis (C), targeting Campylobacter jejuni, though fluoroquinolones are more common. It's effective in non-specific urethritis (D), particularly Chlamydia trachomatis infections, as part of regimens like azithromycin. It's not used for meningococcal meningitis (original E). Clarithromycin's macrolide structure inhibits bacterial protein synthesis, and its improved pharmacokinetics (longer half-life, better tissue penetration) make it versatile for respiratory and soft tissue infections, often in penicillin-allergic patients.

Correct Answer: B

Rationale: Rifampicin accelerates the CYP450-mediated metabolism of warfarin (B), a vitamin K antagonist anticoagulant, reducing its efficacy and requiring dose adjustments to maintain therapeutic INR levels. It also affects corticosteroids (A), like prednisolone, lowering their anti-inflammatory effects. Streptomycin (C), an aminoglycoside, isn't metabolized by CYP450, relying on renal clearance. Digoxin (D) metabolism isn't significantly altered by rifampicin, though P-glycoprotein induction may reduce levels. Oestrogen (original E) metabolism is accelerated, reducing contraceptive efficacy. Rifampicin's potent CYP450 induction, particularly CYP3A4, stems from its activation of the pregnane X receptor, impacting pharmacokinetics of co-administered drugs, critical in TB management where polypharmacy is common.