Moderate
Azithromycin × Clarithromycin
Macrolides×Macrolide antibiotic
Mechanism
Dual macrolide therapy – doubled QT effect and redundant antibacterial activity without clinical rationale.
Symptoms
QT prolongation on ECG. Dizziness, syncope, palpitations. Rarely: polymorphic ventricular tachycardia (torsades de pointes). Risk is higher with hypokalaemia, hypomagnesaemia, bradycardia, and ischaemic heart disease.
Management
The combination is not prescribed. Choose one macrolide: azithromycin for upper respiratory infections and chlamydia (short course); clarithromycin for H. pylori and atypical pneumonia. When choosing, mind the interaction profile (clarithromycin is a strong CYP3A4 inhibitor).
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.