MPharm Master of Pharmacy Master of Pharmacy: Pharmacology and Therapeutics 2

Question 1

A patient on warfarin is started on rifampin. What is the expected pharmacokinetic interaction?

Accepted Answer

Rifampin induces CYP2C9, decreasing warfarin levels

Answer

Rifampin is a potent CYP2C9 inducer that accelerates warfarin metabolism, reducing its anticoagulant effect and requiring dose increases.

Question 2

Which receptor mechanism explains morphine-induced constipation?

Accepted Answer

Activation of mu-opioid receptors in the enteric nervous system

Answer

Mu-opioid receptors in the enteric nervous system mediate decreased GI motility and secretion, causing opioid-induced constipation.

Question 3

A patient with atrial fibrillation and CrCl of 30 mL/min requires anticoagulation. Which DOAC requires the most significant dose adjustment?

Accepted Answer

Dabigatran

Answer

Dabigatran is ~80% renally eliminated and is contraindicated or requires major dose reduction at CrCl <30 mL/min due to accumulation risk.

Question 4

The narrow therapeutic index of lithium requires monitoring for toxicity. Which early sign indicates toxicity?

Accepted Answer

Coarse tremor, nausea, and diarrhea

Answer

Early lithium toxicity (serum level >1.5 mEq/L) presents with coarse tremor, GI disturbances, and drowsiness before progressing to seizures.

Question 5

Which mechanism accounts for resistance to beta-lactam antibiotics in MRSA?

Accepted Answer

Acquisition of mecA gene encoding altered PBP2a

Answer

MRSA expresses PBP2a (encoded by mecA), a modified penicillin-binding protein with low affinity for beta-lactams, conferring resistance.

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