A 50-year-old man is prescribed lisinopril for hypertension. The most common side effect of lisinopril is:

Correct Answer: A

Rationale: The correct answer is A: Dry cough. Lisinopril, an ACE inhibitor, commonly causes a dry, persistent cough due to its effect on bradykinin levels. This side effect is distinct and prevalent compared to others like fatigue, weight gain, or hyperkalemia. Fatigue and weight gain are less common side effects of lisinopril, while hyperkalemia is a potential but less frequent adverse reaction associated with ACE inhibitors. Overall, the prevalence and mechanism of dry cough make it the most common side effect of lisinopril.

Correct Answer: D

Rationale: The correct answer is D: Diphenhydramine. Diphenhydramine is a first-generation antihistamine that can help prevent allergic reactions to contrast media. It works by blocking the action of histamine, which is released during allergic reactions. This drug is commonly used for pre-medication to prevent allergic reactions to contrast media in patients with a history of mild reactions. Choice A (Fluorocortisone) is a corticosteroid and is not typically used for preventing allergic reactions to contrast media. Choice B (Famotidine) is a histamine-2 blocker used for stomach acid reduction and is not indicated for preventing allergic reactions. Choice C (Zafirlukast) is a leukotriene receptor antagonist used for asthma and allergies, but it is not typically used for pre-medication before MRI with contrast media.

Correct Answer: D

Rationale: The correct answer is D because loratadine is a second-generation antihistamine that works by blocking the effects of histamine on peripheral tissues. This helps to alleviate symptoms of allergies such as pruritus and skin wheals. Option A is incorrect because loratadine does not block the release of histamine from mast cells. Option B is incorrect as loratadine does not prevent the antigen-antibody reaction. Option C is incorrect because loratadine does not elicit effects opposite to histamine; instead, it counteracts histamine effects.

Correct Answer: B

Rationale: The correct answer is B: Trigeminal nerve. Sumatriptan is a serotonin receptor agonist that acts on serotonin receptors in the trigeminal nerve to reduce inflammation and pain associated with migraines. The trigeminal nerve is a key player in the pathophysiology of migraines, transmitting pain signals from blood vessels and meninges to the brain. The other choices (A: Nucleus accumbens, C: Vestibular nuclei, D: Chemoreceptor trigger zone) are not directly involved in the pathophysiology of migraines or the mechanism of action of sumatriptan. The nucleus accumbens is primarily associated with reward and motivation, the vestibular nuclei are involved in balance and spatial orientation, and the chemoreceptor trigger zone is related to the regulation of vomiting.

Correct Answer: D

Rationale: Most drugs are absorbed in the GI tract via passive diffusion (Choice D), driven by lipid solubility and concentration gradients across membranes. Active transport (Choice A) requires energy, filtration (Choice B) is minor for drugs, and endocytosis/exocytosis (Choice C) is rare for small molecules.