Moderate
Azithromycin × Mirtazapine
Macrolides×Other antidepressants (NaSSA)
Mechanism
Additive QT prolongation (mirtazapine weakly prolongs QT, especially above 30 mg).
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 (3–5 days) with mirtazapine ≤30 mg, the combination is acceptable. In older patients and cardiovascular disease: ECG before start or alternative antibiotics (doxycycline, a cephalosporin).
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.