Gentamicin, an aminoglycoside:

Correct Answer: B

Rationale: Gentamicin is poorly absorbed from the gut (B), requiring parenteral administration (IV or IM) for systemic infections, due to its polar structure preventing oral bioavailability. It's ineffective in pneumococcal pneumonia (A) caused by Streptococcus pneumoniae, as aminoglycosides target Gram-negative bacteria (e.g., Pseudomonas, E. coli) and have limited Gram-positive activity. Its half-life is about 2-3 hours with normal renal function, not 12 hours (C), though it prolongs in renal impairment, necessitating monitoring. CSF penetration is poor (D), limiting its use in meningitis unless given intrathecally. It can cause irreversible eighth nerve damage (original E), leading to ototoxicity, a known risk with prolonged use. Gentamicin's efficacy in severe Gram-negative infections, like sepsis, relies on its bactericidal action on protein synthesis, but its pharmacokinetics and toxicity profile require careful management.

Correct Answer: B

Rationale: Voriconazole is active against Aspergillus (B), making it a first-line treatment for invasive aspergillosis due to its potent inhibition of ergosterol synthesis via CYP51, with high efficacy against this mold. It's available and effective orally and IV (A), offering flexibility in severe infections. It inhibits cortisol biosynthesis (C), potentially causing adrenal suppression, a rare but notable effect. It inhibits CYP3A (D), leading to significant drug interactions (e.g., with cyclosporine). GI absorption isn't reduced by omeprazole (original E is incorrect). Voriconazole's broad antifungal spectrum, including Candida and Fusarium, and its bioavailability make it critical in immunocompromised patients, though visual disturbances and hepatotoxicity require monitoring.

Correct Answer: D

Rationale: Lymphopenia (D) is an adverse effect of interferons, like interferon alfa, due to bone marrow suppression, reducing lymphocyte counts, common in chronic hepatitis or cancer therapy. Hypocalcemia (A) isn't typical; interferons more often cause flu-like symptoms. Inhibition of spermatogenesis (B) occurs, reflecting gonadal toxicity, but D is highlighted. Renal tubular acidosis (C) isn't a primary effect; nephrotoxicity is rare. Flu-like symptoms (original E) are frequent, including fever and fatigue. Interferons' immunomodulatory and antiproliferative actions explain these effects, activating immune responses while suppressing cell proliferation, necessitating monitoring during prolonged use.

Correct Answer: B

Rationale: Giardia lamblia paired with metronidazole (B) is correct, a first-line treatment for giardiasis, targeting anaerobic protozoa via DNA disruption, with high cure rates. Trypanosoma gambiense with pentamidine and suramin (A) is partially correct; pentamidine or suramin alone is used early, not combined. Taenia saginata with emetine (C) is wrong; praziquantel or niclosamide is standard. Strongyloides with mebendazole (D) is incorrect; ivermectin is preferred. Toxocara canis with pyraquantel (original E) is wrong; albendazole is used. Metronidazole's efficacy in Giardia, amoebiasis, and trichomoniasis reflects its selective anaerobic action, though GI side effects and alcohol intolerance are notable.

Correct Answer: A

Rationale: Pretreatment hydration is mandatory in cisplatin therapy (A), reducing nephrotoxicity by diluting the drug in renal tubules, critical for its safe use in testicular and lung cancers. Dexamethasone and 5HT3 antagonists (B) reduce its high emetogenicity effectively. Visual disturbances (C) are rare; ototoxicity is more common. Magnesium supplements (D) are given for hypomagnesemia from renal loss. Nephrotoxicity is dose-limiting (original E). Cisplatin's DNA cross-linking kills cancer cells, but its renal and auditory toxicity, linked to platinum accumulation, demands aggressive hydration and electrolyte management.