General Pharmacology: 30 Mcqs For Chapters 15 Medical Students Practice

MCQs General Pharmacology: pharmacokinetics & pharmacodynamics 1. A 65-year-old patient with chronic kidney disease is prescribed digoxin for heart failure. The patient is also taking verapamil for hypertension. Considering pharmacokinetic and pharmacodynamic principles, which of the following statements is most accurate regarding the digoxin therapy? A. Digoxin clearance will increase due to verapamil, lowering the risk of toxicity. B. Verapamil will inhibit renal tubular secretion of digoxin, increasing plasma levels and toxicity risk. C. Digoxin and verapamil interact via first-pass metabolism, reducing bioavailability. D. The combination causes chemical antagonism at the digoxin receptor. E. Verapamil induces CYP450 enzymes, leading to subtherapeutic digoxin levels. Answer: B Explanation: Digoxin is primarily excreted by renal tubular secretion. Verapamil inhibits P-glycoprotein in renal tubules, reducing digoxin clearance plasma concentration toxicity. A is wrong because clearance decreases, not increases. C is incorrect: interaction is not via first-pass metabolism. D is wrong: its not chemical antagonism. E is incorrect: digoxin is not metabolized significantly by CYP450; verapamil is an inhibitor, not inducer.2. A new orally administered drug is highly lipid-soluble, weakly acidic (pKa = 5.0), and extensively metabolized by CYP3A4 in the gut and liver. Which combination of pharmacokinetic phenomena will most significantly reduce its oral