oseltamivir + warfarin

A combination of **oseltamivir**, an antiviral neuraminidase inhibitor used primarily for the treatment and prophylaxis of influenza A and B, and **warfarin**, an oral anticoagulant that inhibits vitamin K-dependent clotting factors and is used to prevent and treat thromboembolic disorders. Oseltamivir acts by inhibiting the viral neuraminidase enzyme, thus preventing the release of new viral particles. Warfarin exerts its effect by inhibiting the synthesis of vitamin K-dependent clotting factors II, VII, IX, and X, thereby impeding the coagulation cascade. Concomitant use of oseltamivir and warfarin is not considered a standard fixed-dose combination product; however, these medications may be co-administered in clinical practice, especially in patients with comorbidities (e.g., cardiovascular disease and influenza). Limited evidence suggests a possible interaction that may lead to increased INR and risk of coagulopathy, but the mechanism is not well defined and is not generally recognized as clinically significant; careful monitoring of INR is advised when initiating or discontinuing oseltamivir in patients stabilized on warfarin[1][2][3][4][5][6][7].