Major
Probable
Description
Both azithromycin and ciprofloxacin prolong the QT interval; concurrent or overlapping use significantly increases torsades de pointes risk.
Mécanisme
Both drugs inhibit cardiac hERG potassium channels; additive IKr blockade prolongs ventricular repolarization beyond what either agent causes alone.
Signification clinique
The combination of two QT-prolonging antibiotics is particularly risky in patients with hypokalemia or structural heart disease.
Prise en charge
Avoid concurrent use; select antibiotics with complementary spectra but non-overlapping QT risk; monitor ECG if co-administration is necessary.