Which antibiotic class is associated with prolonged QT intervals?

Which antibiotic class is associated with prolonged QT intervals?

• A. Fluoroquinolones
• B. Penicillins
• C. Aminoglycosides
• D. Macrolides

Answer: (D)

Prolonged QT intervals result from drugs that delay ventricular repolarization, increasing the risk of torsades de pointes in susceptible individuals. Macrolide antibiotics have the strongest, well-established association with QT prolongation—especially erythromycin and clarithromycin, with azithromycin also having some risk. The mechanism involves effects on cardiac potassium channels (notably the hERG current) that prolong the QT by delaying repolarization. Risk rises with higher doses, electrolyte abnormalities (low potassium or magnesium), female sex, older age, congenital long QT, and concomitant QT-prolonging drugs. While some other antibiotics can affect the QT interval, macrolides are the class most clearly linked to this issue. Penicillins and aminoglycosides are not typically associated with QT prolongation.

Prolonged QT intervals result from drugs that delay ventricular repolarization, increasing the risk of torsades de pointes in susceptible individuals. Macrolide antibiotics have the strongest, well-established association with QT prolongation—especially erythromycin and clarithromycin, with azithromycin also having some risk. The mechanism involves effects on cardiac potassium channels (notably the hERG current) that prolong the QT by delaying repolarization. Risk rises with higher doses, electrolyte abnormalities (low potassium or magnesium), female sex, older age, congenital long QT, and concomitant QT-prolonging drugs. While some other antibiotics can affect the QT interval, macrolides are the class most clearly linked to this issue. Penicillins and aminoglycosides are not typically associated with QT prolongation.