MajorTricyclic antidepressants (TCA)×Fluoroquinolone antibacterials
Updated · Methodology
Mechanism
Additive QT prolongation. Ciprofloxacin additionally blocks CYP1A2 – an amitriptyline metabolic route. Amitriptyline plasma levels rise.
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 without QT effect: a cephalosporin or nitrofurantoin. 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: Cipro (ciprofloxacin hydrochloride) prescribing information (2016)– ; DailyMed setid 888dc7f9-ad9c-4c00-8d50-8ddfd9bd27c0
- AEMPS: Ficha técnica: Amitriptilina (nº registro 89862), sección 4.5 (2026)– AEMPS, CIMA, nº registro 89862, revisión 05/2026, sección 4.5
- AEMPS: Ficha técnica: Ciprofloxacino (nº registro 62765), sección 4.5 (2025)– AEMPS, CIMA, nº registro 62765, revisión 11/2025, sección 4.5