Major
Carbamazepine × Rivaroxaban
Antiepileptics. Carboxamide derivatives×Direct oral anticoagulants (factor Xa inhibitors)
Mechanism
Carbamazepine induces CYP3A4 and P-glycoprotein – two rivaroxaban clearance routes. Rivaroxaban plasma levels fall by 50%; anticoagulant effect weakens.
Symptoms
The patient feels nothing. Stroke risk in atrial fibrillation rises, as do deep vein thrombosis and pulmonary embolism risks.
Management
Avoid the combination. Alternative anticoagulants: warfarin with INR monitoring or low molecular weight heparin. Alternative anticonvulsants without induction: levetiracetam, lamotrigine.