Which CAP antibiotic is associated with QT interval prolongation leading to ventricular fibrillation?

Which CAP antibiotic is associated with QT interval prolongation leading to ventricular fibrillation?

• A. Amoxicillin
• B. Azithromycin
• C. Ceftriaxone
• D. Doxycycline

Answer: (B)

QT interval prolongation is a recognized risk with certain antibiotics, especially macrolides. Azithromycin, a macrolide commonly used for community-acquired pneumonia, can slow cardiac repolarization by blocking specific potassium channels (hERG), which lengthens the QT interval. This increases the chance of developing torsades de pointes and, in rare cases, ventricular fibrillation, particularly in patients with electrolyte abnormalities, other QT‑prolonging drugs, or preexisting QT prolongation. Among the listed options, azithromycin is the one most associated with this risk, making it the best answer. The other antibiotics—amoxicillin, ceftriaxone, and doxycycline—do not carry a meaningful risk of QT prolongation or ventricular arrhythmias through this mechanism.

QT interval prolongation is a recognized risk with certain antibiotics, especially macrolides. Azithromycin, a macrolide commonly used for community-acquired pneumonia, can slow cardiac repolarization by blocking specific potassium channels (hERG), which lengthens the QT interval. This increases the chance of developing torsades de pointes and, in rare cases, ventricular fibrillation, particularly in patients with electrolyte abnormalities, other QT‑prolonging drugs, or preexisting QT prolongation. Among the listed options, azithromycin is the one most associated with this risk, making it the best answer. The other antibiotics—amoxicillin, ceftriaxone, and doxycycline—do not carry a meaningful risk of QT prolongation or ventricular arrhythmias through this mechanism.