NAPLEX QBANK Drug Interactions and Adverse Effects

Question 1

A patient stabilized on an SSRI is prescribed tramadol for acute pain. Which serious adverse reaction is most likely to result from this combination?

Accepted Answer

Serotonin syndrome

Answer

Both SSRIs and tramadol increase serotonergic activity, and their concurrent use can precipitate serotonin syndrome characterized by hyperthermia, autonomic instability, and neuromuscular abnormalities.

Question 2

A patient stabilized on warfarin begins amiodarone therapy for atrial fibrillation. What dose adjustment to warfarin is typically required?

Accepted Answer

Decrease warfarin dose by 30–50%

Answer

Amiodarone inhibits CYP2C9, the primary enzyme responsible for metabolizing warfarin's active S-enantiomer, resulting in elevated INR and requiring a 30–50% reduction in warfarin dose.

Question 3

Which antibiotic class most significantly inhibits CYP3A4 and increases the risk of statin-induced rhabdomyolysis?

Accepted Answer

Macrolides

Answer

Macrolides such as clarithromycin and erythromycin inhibit CYP3A4, reducing statin metabolism, elevating plasma statin concentrations, and markedly increasing the risk of myopathy and rhabdomyolysis.

Question 4

What is the primary mechanism by which NSAIDs increase the toxicity of low-dose methotrexate?

Accepted Answer

Competing with methotrexate for renal tubular secretion

Answer

NSAIDs compete with methotrexate for renal tubular secretion via OAT transporters, reducing its elimination and causing dangerous accumulation and toxicity.

Question 5

Which drug combination is most likely responsible for a patient developing a prolonged QTc interval on ECG?

Accepted Answer

Azithromycin and haloperidol

Answer

Both azithromycin and haloperidol independently prolong the QT interval by blocking cardiac hERG potassium channels; their combination synergistically increases the risk of torsades de pointes.

NAPLEX QBANK Practice Test

NAPLEX QBANK Practice Test

NAPLEX QBANK Drug Interactions and Adverse Effects