Interaction of fluvoxamine with warfarin in an elderly woman

An 80-year-old woman presented with an embolic stroke secondary to atrial fibrillation and mitral stenosis. She was initially on intravenous heparin and was subsequently maintained on oral warfarin. She was also given digoxin for atrial fibrillation and colchicine for gouty arthritis as well as fluvoxamine in her fourth week in hospital, to treat her depression. However, her INR (international normalised ratio) became markedly elevated within a week. Fluvoxamine and warfarin were stopped immediately. When warfarin was reintroduced 6 days later, her INR value increased again. The coagulation profile only became stable after 2 weeks of cessation of fluvoxamine. Low dose fluvoxamine can interact significantly with warfarin in the elderly and the effect may persist for up to 2 weeks of stopping the antidepressant.