Interaction of ibuprofen and warfarin on primary haemostasis.

It has been stated that ibuprofen can be safely prescribed with concomitant warfarin. The effect of ibuprofen on primary haemostasis was investigated in 20 patients on warfarin for venous thromboembolism. Ibuprofen, 600 mg orally t.i.d., was added for 1 week. Bleeding time, prothrombin time, platelet count and urinalysis for haemoglobin were performed before and 90 minutes after the first dose and after 1 week. The bleeding time was significantly prolonged after 90 minutes (p less than 0.01) and after 1 week (p less than 0.05) and in four cases it was prolonged above the normal range. No clinical side-effects were observed apart from microscopic haematuria and haematoma. Thus, ibuprofen may cause clinical problems in some patients treated with warfarin, particularly in the elderly on complex drug regimens. It is advisable to check the bleeding time a few days after treatment with ibuprofen has been started in patients already on oral anticoagulation, and discontinue the former if the bleeding time is prolonged above the normal range.