MajorTricyclic antidepressants (TCA)×Macrolide antibiotic
Updated · Methodology
Mechanism
Clarithromycin blocks CYP3A4 and prolongs QT itself. Amitriptyline plasma levels rise; additive QT risk.
Symptoms
QT prolongation on ECG. Dizziness, syncope, palpitations. Severe cases: polymorphic ventricular tachycardia (torsades de pointes). Risk is higher with hypokalaemia and hypomagnesaemia.
Management
Avoid the combination. Alternative antibiotics: azithromycin or doxycycline (minimal CYP3A4 and QT effect). Alternative for neuropathic pain instead of TCA: gabapentin or pregabalin.
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.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- FDA: Clarithromycin tablet (Solaris Pharma Corporation) – Prescribing Information (2017)– ; DailyMed setid 4d42821d-ce7a-7d64-e063-6294a90a0875
- AEMPS: Ficha técnica: Amitriptilina (nº registro 89862), sección 4.5 (2026)– AEMPS, CIMA, nº registro 89862, revisión 05/2026, sección 4.5