Do Fluoroquinolones Predispose Patients to Serious Cardiac Arrhythmias?

Fluoroquinolones kill bacteria by inhibiting DNA gyrase. They also downregulate a gene involved in cardiac repolarization, which can cause prolongation of the QT interval. Some fluoroquinolones have been withdrawn from the market because of their cardiac toxicity, but the cardiac risks of those currently in clinical use remain controversial.

Scandinavian investigators probed national medical databases to quantitate risk for arrhythmia among adults (age range, 40–79) who were treated with fluoroquinolones in Denmark (1997–2001) and Sweden (2006–2013). Only 66 instances of arrhythmia were identified during or after more than 900,000 fluoroquinolone courses. This low rate was nearly identical to the rate of arrhythmia in an equally large control group that received penicillin V (a drug without cardiac toxicity that was standard treatment for respiratory infection in these countries). The patient cohorts were well matched for a long list of medical conditions and concomitant medications; in subgroup analyses, no characteristics were identified that conferred excess risk for fluoroquinolone-associated arrhythmia. The most commonly prescribed fluoroquinolones were ciprofloxacin (in 83% of courses) and norfloxacin (in 12% of courses).