Major
Rifampicin × Rivaroxaban
Antituberculous antibiotic×Direct oral anticoagulants (factor Xa inhibitors)
Mechanism
Rifampicin strongly induces CYP3A4 and P-glycoprotein – two rivaroxaban clearance routes. Rivaroxaban plasma levels fall by 50%; anticoagulant effect weakens.
Symptoms
The patient feels nothing. Thromboembolic risk rises: stroke in atrial fibrillation, deep vein thrombosis, pulmonary embolism.
Management
The combination is not prescribed. Alternative anticoagulants: warfarin with INR monitoring (rifampicin also weakens warfarin, but titration is easier) or low molecular weight heparin for short courses. Induction persists for 2 weeks after rifampicin stops.