1. A patient taking carbamazepine develops reduced anticoagulant effects after starting another medication. Which pharmacokinetic mechanism best explains this interaction?
A. Inhibition of CYP2C9-mediated metabolism
B. Competitive inhibition of renal tubular secretion
C. Inhibition of intestinal P-glycoprotein
D. Induction of hepatic drug-metabolising enzymes
2. Which of the following best explains why methotrexate toxicity can be increased by concomitant administration of trimethoprim?
A. Both drugs inhibit dihydrofolate reductase
B. Trimethoprim accelerates methotrexate glucuronidation
C. Both drugs inhibit xanthine oxidase
D. Methotrexate increases trimethoprim renal filtration
D
A
D
A
D
A
D
A
D
A