Direct oral anticoagulants (factor Xa inhibitors)×Antiepileptic, hydantoin derivative (sodium channel blocker)
Mechanism
Phenytoin is a strong CYP3A4 + P-gp inducer. Apixaban level falls 50–75% with loss of anticoagulation and risk of stroke or VTE recurrence. FDA Eliquis Section 7.
Symptoms
Ischemic stroke in atrial fibrillation patient or recurrent venous thrombosis.
Management
Combination contraindicated. Alternative anticoagulant: warfarin (INR 2.0–3.0 in AF). Alternative anticonvulsant: levetiracetam (no induction).
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.