Lack of effect of fluoxetine on the hypoprothrombinemic response of warfarin.

The purpose of this study was to assess the effect of fluoxetine on the hypoprothrombinemic response of warfarin in patients chronically anticoagulated. Patients receiving low-intensity anticoagulation with warfarin were recruited. All patients were taking stable dosages of warfarin and had two baseline prothrombin times (PTs) within 10% of each other. Each patient received fluoxetine (20 mg daily) for 21 days. PTs were measured on days 2, 5, 8, 12, 15, 19, and 22 of fluoxetine administration. Six patients completed the study. There was no significant difference in mean PTs before and during fluoxetine administration. Fluoxetine at the dosage studied does not predictably effect the hypoprothrombinemic response of warfarin.