NAPLEX QBANK Drug Interactions and Adverse Effects 2

Question 1

A patient on metformin is scheduled for a CT scan requiring iodinated contrast. What is the primary pharmacokinetic concern?

Accepted Answer

Contrast-induced nephropathy impairs metformin excretion, raising lactic acidosis risk

Answer

Iodinated contrast can precipitate acute kidney injury, which impairs metformin's renal elimination; the resulting metformin accumulation shifts glucose metabolism toward anaerobic pathways and risks potentially fatal lactic acidosis.

Question 2

Which serious musculoskeletal adverse effect is most strongly associated with fluoroquinolone antibiotics, particularly in elderly patients?

Accepted Answer

Tendinopathy and tendon rupture

Answer

Fluoroquinolones disrupt tenocyte metabolism and matrix metalloproteinase activity, predisposing tendons — most commonly the Achilles tendon — to degeneration and rupture, especially in older patients and those on corticosteroids.

Question 3

Rifampin is a potent inducer of which CYP450 isoenzyme, accounting for the majority of its clinically significant drug interactions?

Accepted Answer

CYP3A4

Answer

Rifampin is among the most potent inducers of CYP3A4, the most abundant hepatic CYP enzyme, dramatically increasing the metabolism of drugs such as oral contraceptives, warfarin, antiretrovirals, and cyclosporine.

Question 4

A post-MI patient is taking both warfarin and clopidogrel. What is the primary clinical concern of this combination?

Accepted Answer

Substantially increased risk of major bleeding

Answer

Warfarin reduces clotting factor synthesis while clopidogrel inhibits platelet aggregation; their combination produces additive antithrombotic effects and significantly elevates the risk of major hemorrhagic events.

Question 5

Why does hypokalemia potentiate digoxin toxicity?

Accepted Answer

Potassium and digoxin compete for the same binding site on Na+/K+-ATPase

Answer

Potassium competes with digoxin for binding to the cardiac Na+/K+-ATPase; when serum potassium is low, digoxin binds more avidly to the pump, amplifying both therapeutic and toxic effects at normal drug concentrations.

NAPLEX QBANK Practice Test

NAPLEX QBANK Practice Test

NAPLEX QBANK Drug Interactions and Adverse Effects 2