Amitriptyline × Azithromycin

Both drugs prolong the QT interval. Azithromycin, like other macrolides, prolongs cardiac repolarisation and the QT interval, which carries a risk of torsades de pointes (azithromycin SmPC). QT prolongation and arrhythmias have been reported with amitriptyline, and its SmPC lists QT-prolonging drugs among combinations that are not recommended: with tricyclic antidepressants they increase the likelihood of ventricular arrhythmias (amitriptyline SmPC).

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.

The amitriptyline SmPC lists QT-prolonging drugs among combinations that are not recommended (amitriptyline SmPC). Azithromycin is used with caution in patients who take QT-prolonging drugs and in those with QT prolongation, low potassium or magnesium, clinically relevant bradycardia, arrhythmia, severe heart failure and in older people (azithromycin SmPC). The US Food and Drug Administration (FDA) asks prescribers to weigh the risk of QT prolongation against the benefit of azithromycin in these patients (azithromycin FDA label). Avoid the combination where possible. If it is still needed, keep in mind that with amitriptyline the arrhythmia risk is higher with marked bradycardia, uncompensated heart failure and potassium or magnesium disturbances (amitriptyline SmPC).