Major
Ciprofloxacin × Dronedarone
Fluoroquinolone antibacterials×Class III antiarrhythmic
Mechanism
Additive QT prolongation. Dronedarone is on the FDA list of drugs that contraindicate strong QT-prolonging antibiotics. Ciprofloxacin prolongs QT dose-dependently.
Symptoms
QT prolongation on ECG. Clinically: dizziness, syncope, palpitations. Severe cases progress to polymorphic ventricular tachycardia (torsades de pointes) with risk of ventricular fibrillation and sudden cardiac death. Risk is higher with hypokalaemia, hypomagnesaemia, bradycardia, and ischaemic heart disease.
Management
Avoid the combination. Alternative antibiotics: a cephalosporin (no QT effect) or nitrofurantoin for urinary tract infection.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.