Which medication class is most likely to cause QT interval prolongation?

Which medication class is most likely to cause QT interval prolongation?

• A. Macrolide antibiotics (e.g., azithromycin)
• B. Proton pump inhibitors
• C. Beta-blockers
• D. Diuretics

Answer: (A)

Meds that prolong the QT interval do so by delaying the heart’s repolarization, often through interference with potassium channels involved in repolarization (IKr/hERG channels). Macrolide antibiotics can do this, and they’re a classic example of a drug class associated with QT prolongation. This can raise the risk of torsades de pointes, especially in people with electrolyte disturbances, preexisting long QT, or when combined with other QT-prolonging drugs. Proton pump inhibitors aren’t known for prolonging the QT interval. Beta-blockers don’t typically affect QT duration, though they influence heart rate and conduction. Diuretics can contribute indirectly by causing electrolyte losses (like low potassium or magnesium), which can increase torsades risk, but they don’t directly prolong the QT interval as a primary action in the same way macrolide antibiotics do.

Meds that prolong the QT interval do so by delaying the heart’s repolarization, often through interference with potassium channels involved in repolarization (IKr/hERG channels). Macrolide antibiotics can do this, and they’re a classic example of a drug class associated with QT prolongation. This can raise the risk of torsades de pointes, especially in people with electrolyte disturbances, preexisting long QT, or when combined with other QT-prolonging drugs.

Proton pump inhibitors aren’t known for prolonging the QT interval. Beta-blockers don’t typically affect QT duration, though they influence heart rate and conduction. Diuretics can contribute indirectly by causing electrolyte losses (like low potassium or magnesium), which can increase torsades risk, but they don’t directly prolong the QT interval as a primary action in the same way macrolide antibiotics do.