Uses of clarithromycin include:

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: A

Rationale: Terbinafine is indicated in dermatophyte nail infections (A), such as onychomycosis, due to its fungicidal action against Trichophyton and other dermatophytes, accumulating in keratin-rich tissues for prolonged effect. Topical forms treat ringworm (B), like tinea pedis or cruris, effectively. A single dose isn't usually effective (C); oral therapy requires weeks to months. It's not a potent CYP450 inducer (D), though it inhibits CYP2D6, affecting some drugs. It may exacerbate psoriasis (original E). Terbinafine's allylamine mechanism disrupts ergosterol synthesis early, offering high cure rates in superficial fungal infections, with minimal systemic toxicity compared to azoles.

Correct Answer: B

Rationale: AZT + lamivudine + lopinavir/ritonavir (B) is an accepted first-line HIV therapy, combining two nucleoside reverse transcriptase inhibitors (NRTIs: AZT, lamivudine) with a boosted protease inhibitor (lopinavir/ritonavir), effectively suppressing viral replication and preventing resistance. AZT + ddC (A) lacks a third class, reducing efficacy. Ritonavir + amprenavir + enfuvirtide (C) mixes protease inhibitors and an entry inhibitor, not typical first-line. AZT + lamivudine + nevirapine (D), with an NNRTI, is viable but less common now versus integrase inhibitors. Modern guidelines favor integrase-based regimens (e.g., dolutegravir), but B reflects older, still-accepted triple therapy, balancing potency and resistance barriers.

Correct Answer: B

Rationale: Melphalan (B) is associated with profound and prolonged myelosuppression, an alkylating agent causing dose-limiting neutropenia and thrombocytopenia, common in multiple myeloma treatment. Chlorambucil (A) causes milder, reversible suppression. BCNU (C), or carmustine, also causes severe, delayed myelosuppression, notable in brain tumors. Bleomycin (D) primarily causes pulmonary toxicity, not myelosuppression. Vincristine (original E) affects nerves, not marrow. Melphalan's DNA cross-linking halts cell division, effective in hematologic malignancies, but its marrow toxicity requires growth factor support or dose delays, balancing efficacy with infection risk.

Correct Answer: C

Rationale: Recombinant human erythropoietin (EPO) treats anemia of chronic renal failure (C), stimulating red blood cell production in kidneys unable to produce endogenous EPO, improving quality of life in dialysis patients. It's not used for iron-deficient anemia (A); iron supplementation is needed. Sickle cell anemia (B) relies on hydroxyurea, not EPO. It treats AZT-related anemia (D) in HIV, countering marrow suppression. It's ineffective in clozapine-induced agranulocytosis (original E). EPO's targeted stimulation of erythropoiesis, monitored via hemoglobin levels, reduces transfusion needs, though hypertension and thrombosis risks require oversight.