warfarin and apixaban

Pharmacodynamic interaction: both drugs impair haemostasis. Warfarin inhibits vitamin K-dependent clotting factors II, VII, IX, X. Apixaban directly inhibits factor Xa. The combination produces additive anticoagulant effects, markedly increasing bleeding risk.

Concurrent use significantly increases the risk of major haemorrhage, including intracranial and gastrointestinal bleeding, which can be life-threatening. The risk is higher in patients with additional risk factors such as age, renal impairment, or concomitant antiplatelet therapy.

Co-prescription is contraindicated. If switching therapy, discontinue one agent and start the other according to an accepted transition protocol, with close monitoring of INR and clinical bleeding signs. Do not overlap the agents except during supervised switching.

Well-established from pharmacology and clinical experience; guidelines recommend avoiding concurrent use of vitamin K antagonists and direct oral anticoagulants.