Adverse Drug Reactions and Interactions · USMLE Step 1

Which combination is especially dangerous due to additive risk of QT prolongation and torsades de pointes?

  1. Warfarin + aspirin
  2. Macrolide antibiotic + antiarrhythmic
  3. ACE inhibitor + diuretic
  4. Beta-blocker + calcium channel blocker
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Correct answer: Macrolide antibiotic + antiarrhythmic

Some macrolides and antiarrhythmic drugs both prolong the QT interval. When combined, this additive effect increases risk of torsades de pointes and sudden cardiac death.

Difficulty: Medium Question 6 of 19

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