Major
Azithromycin × Haloperidol
Macrolides×First-generation antipsychotics. Butyrophenone derivatives
Mechanism
Additive QT prolongation. Azithromycin received a 2013 FDA warning for fatal arrhythmia risk. Haloperidol (especially IV) also has a pronounced QT effect.
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: doxycycline or a cephalosporin. Alternative antipsychotics with minimal QT effect: olanzapine or aripiprazole.
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.