Proton pump inhibitors may increase the risk of delayed bleeding complications after open heart surgery if used concomitantly with warfarin.

OBJECTIVES The American Food and Drug Administration has suggested that proton pump inhibitors increase the international normalized ratio (INR) when used concomitantly with warfarin, by being metabolized by cytochrome P450 2C19. We therefore reviewed patients taking warfarin. METHODS AND RESULTS Two hundred and forty patients who took warfarin after surgery were divided into two groups: Group I (n = 114) had rabeprazole (10 mg/day) and Group II (n = 126) had lansoprazole (15 mg/day). The initial dose of warfarin was 3 mg and INR was initially assessed on postoperative day 4. Initial INR was significantly lower in Group I (1.66 +/- 0.87) than in Group II (2.06 +/- 1.03, P = 0.0011). Delayed cardiac tamponade and hemothorax occurred as complications in 6 and 1 patients, respectively, in Group II from 5 days to 3 months postoperatively. At the time of the occurrence of complications, the average INR increased to 3.95 (range from 3.11 to 5.86). There were no patients with delayed bleeding in Group I ( P = 0.015). CONCLUSIONS These results suggest that lansoprazole emphasizes the effects of warfarin. Rabeprazole could be safely used concomitantly with warfarin.