A 52-year-old woman with multiple endocrine neoplasia syndromes has a large pancreatic tumor and bilateral adrenal tumors. She is hospitalized on the medicine service. The tumor is considered inoperable. Her blood pressure is $180 / 100 \mathrm{~mm} \mathrm{Hg}$. In addition to intravenous fluids, this patient may benefit from which of the following interventions?

Correct Answer: D

Rationale: Phentolamine IV (D) benefits this patient with likely pheochromocytoma (adrenal tumors, hypertension 180/100), an $\alpha$-blocker reversing catecholamine-induced vasoconstriction rapidly, critical in MEN syndromes. Oral analgesics (A) and transdermal (B) address pain, not BP. Phenoxybenzamine (C) is oral, slower. Tolterodine (original E) is irrelevant. Phentolamine's IV onset controls acute hypertensive crises, stabilizing for surgery or palliation, a key intervention in endocrine emergencies.

Correct Answer: C

Rationale: Phenytoin (C) exhibits non-linear kinetics, with saturable hepatic metabolism (CYP2C9) causing half-life to increase at high doses (e.g., >300 mg/day). Aspirin overdose (A) and ethanol (D) are zero-order at high levels, also correct but C is chosen. Heparin (B) is complex, not purely non-linear. Ceftazidime (original E) is first-order. Non-linear kinetics, as with phenytoin, complicate dosing (e.g., toxicity risk), requiring monitoring, unlike linear drugs with predictable clearance.

Correct Answer: A

Rationale: Oxytetracycline (A) has increased bioavailability fasting, as food (e.g., calcium) chelates it, reducing absorption. Amoxicillin (B) is unaffected. Levodopa (C) competes with dietary amino acids, correct but A is chosen. Acetylsalicylic acid (D) and fluconazole (original E) are minimally impacted. Fasting enhances tetracycline uptake, critical in antibiotic therapy, avoiding food interactions that lower efficacy, a practical dosing consideration.

Correct Answer: A

Rationale: Ciclosporin (A) is a CYP3A substrate, metabolized in the liver, affecting its immunosuppressive levels (e.g., transplant therapy). Clarithromycin (B) is too, also correct but A is chosen. Phenytoin (C) uses CYP2C9. Adrenaline (D) is COMT/MAO-metabolized. Warfarin (original E) is CYP2C9. CYP3A's broad substrate range, critical in drug interactions (e.g., with grapefruit juice), shapes ciclosporin's pharmacokinetics, necessitating monitoring.

Correct Answer: D

Rationale: Smaller digoxin doses are required in severe renal failure (D), as its renal clearance (GFR <10 mL/min) drops, prolonging half-life, risking toxicity. Option A is false (pH may rise). Option B is incorrect (phenytoin range adjusts minimally). Option C lacks evidence. Option E (original) about omeprazole is false. Digoxin's renal dependence, critical in heart failure, necessitates adjustment, a key pharmacokinetic shift in renal impairment.