ModerateTricyclic antidepressants (TCA)×Vitamin K antagonist anticoagulants
Updated · Methodology
Mechanism
Amitriptyline is metabolised via CYP2C9 (a minor route) – weak competition with warfarin is possible. Mild INR rises have been reported when adding a TCA.
Symptoms
Mostly no changes. In some patients: a 10–15% INR rise 2–4 weeks after starting amitriptyline.
Management
After starting amitriptyline, check INR at 2 and 4 weeks, then resume routine monitoring. If INR rises above target, reduce warfarin by 5–10%. Alternative antidepressants without CYP2C9 dependence: sertraline or agomelatine.
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: Warfarin sodium tablet (Amneal Pharmaceuticals LLC) – Prescribing Information (2017)– ; DailyMed setid 558b7a0d-5490-4c1b-802e-3ab3f1efe760
- FDA: Amitriptyline hydrochloride tablet (Sun Pharmaceutical Industries, Inc.) – Prescribing Information (2014)– ; DailyMed setid 4e520c63-1cf6-40f6-a51c-3f9b0e181342