Moderate
Azithromycin × tacrolimus
Macrolides×Calcineurin inhibitor (immunosuppressant)
Mechanism
Additive QT prolongation (tacrolimus prolongs QT in hypomagnesaemia, common on calcineurin inhibitors).
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
For short azithromycin courses post-transplant: check magnesium and replete if needed. ECG before start if other QT-prolonging drugs are on board. Alternative antibiotics: a cephalosporin or doxycycline.
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.