MajorAntiepileptics. Carboxamide derivatives×Vitamin K antagonist anticoagulants
Updated · Methodology
Mechanism
Carbamazepine strongly induces CYP2C9 and CYP3A4. Warfarin plasma levels fall by 50–70% over 2–4 weeks; anticoagulant effect weakens.
Symptoms
INR drops below target. Thromboembolic risk rises: deep vein thrombosis, pulmonary embolism, ischaemic stroke in atrial fibrillation.
Management
After starting carbamazepine, check INR every 1–2 weeks for the first month and titrate warfarin (usually 1.5- to 2-fold dose increase). On carbamazepine withdrawal, induction persists for 2–4 weeks – return warfarin gradually. Alternative anticonvulsants without induction: levetiracetam, lamotrigine.
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: Tegretol (carbamazepine) prescribing information (2023)– ; DailyMed setid 8d409411-aa9f-4f3a-a52c-fbcb0c3ec053
- AEMPS: Ficha técnica: Carbamazepina (nº registro 62621), sección 4.5 (2025)– AEMPS, CIMA, nº registro 62621, sección 4.5
- AEMPS: Ficha técnica: Warfarina (Aldocumar 5 mg) (nº registro 63064), sección 4.5 (2023)– AEMPS, CIMA, nº registro 63064, revisión 01/2023, sección 4.5