Moderate
Amitriptyline × Warfarin
Tricyclic antidepressants (TCA)×Vitamin K antagonist anticoagulants
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.