Major
Azithromycin × citalopram
Macrolides×SSRI (selective serotonin reuptake inhibitor)
Mechanism
Additive QT prolongation. Less dangerous than citalopram with clarithromycin (azithromycin prolongs QT less), but risk persists, especially with risk factors.
Symptoms
QT prolongation on ECG. Clinically: dizziness, syncope, palpitations. Severe cases progress to 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 normal potassium and magnesium, the combination is acceptable. In atrial fibrillation, hypokalaemia, or prior QT prolongation, alternative antibiotics (doxycycline, a cephalosporin).