[Skip to Content]
[Skip to Content Landing]
April 1980

Potentiation of Warfarin Anticoagulation by Sulfisoxazole

Author Affiliations

From the Departments of Emergency Medicine (Dr Sioris) and Internal Medicine (Dr Pentel), Hennepin County Medical Center and University of Minnesota School of Medicine and College of Pharmacy (Drs Sioris and Weibert), Minneapolis. Dr Weibert is now with the School of Pharmacy, University of California San Francisco-San Diego Program, San Diego.

Arch Intern Med. 1980;140(4):546-547. doi:10.1001/archinte.1980.00330160106038

• The prothrombin time (PT) of a patient undergoing warfarin sodium anticoagulation became elevated when sulfisoxazole was given concurrently. The warfarin dose index is used to demonstrate that this PT prolongation was the result of a warfarin-sulfisoxazole interaction. The mechanism of this interaction may involve displacement of warfarin from serum albumin. Sulfisoxazole should be used cautiously, if at all, in patients taking warfarin.

(Arch Intern Med 140:546-547, 1980)