A 75-year-old man has a fever of 104°F. He develops a cough that produces blood-tinged sputum with gram-positive cocci in clusters. Which of the following penicillins is likely to fail to treat this infection adequately?

Correct Answer: D

Rationale: Ticarcillin is less effective against gram-positive cocci (e.g., Staphylococcus) compared to the anti-staphylococcal penicillins listed.

Correct Answer: D

Rationale: Acute iron toxicity is managed with gastric lavage using bicarbonate to bind iron, reducing absorption. Hydroxocobalamin is not preferred for absorption speed but for cyanide poisoning; ferrous iron is better absorbed; ascorbic acid enhances iron absorption; dialysis patients often need folic acid.

Correct Answer: D

Rationale: Rivaroxaban has a rapid onset, no INR monitoring, fewer CYP450 interactions, and a shorter duration (half-life ~5-9 hours) than warfarin, but it is not safe in severe renal impairment due to renal excretion, requiring dose adjustment.

Correct Answer: B

Rationale: Cilostazol inhibits phosphodiesterase III, increasing cAMP (not breaking it down), leading to vasodilation and antiplatelet effects. It’s used for intermittent claudication, and headache is a common side effect.

Correct Answer: D

Rationale: Bisphosphonates reduce bone turnover in Paget’s, inhibit farnesyl pyrophosphate synthase for osteoclast apoptosis, and cause esophagitis (mitigated by upright posture), but they’re contraindicated in severe renal dysfunction due to accumulation.