This question comes from the American Society for Clinical Laboratory Science Consumer Information Forum and was forwarded to Fritsma Factor by Prof. Bernadette (Bunny) Rodak of Indiana University. It is modified to mask the identity of the inquirer.
“I have been on 5 mg/day of Coumadin for three months following hip replacement surgery and my INR is stable and therapeutic. My doctor says I should limit myself to two alcoholic beverages a day but that I should have those two every day. I do not like to have a drink every day and my question is, “What harm can come if I do not drink for a week or two and then have four or five in one evening?”
Bunny, I thought this would be an easy one, but there seems to be conflicting information. One review; Cropp JS, Bussey HI. A review of enzyme induction of warfarin metabolism with recommendations for patient management. Pharmacotherapy 1997;17:917-28 states, “A suspected interaction may occur with smoking and long-term alcohol consumption. Ingestion of a small amount of alcohol is unlikely to interact with warfarin.” Another; Wells PS, Holbrook AM, Crowther NR, Hirsh J.Interactions of warfarin with drugs and food. Ann Intern Med 1994;121:676-83 says alcohol, only in association with liver disease, potentiates warfarin and increases bleeding risk. In Ansell J, Hirsh J, Poller L, et al. The pharmacology and management of the vitamin K antagonists; The seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004;126:204S-33S, which is the bible of antithrombotic therapy, alcohol is listed as a potentiator of warfarin in association with liver disease and as having no effect when there is no liver disease.
I remember reading somewhere that binge drinking during warfarin therapy could lead to bleeding, however that may probably be due to the anti-platelet effect of alcohol, which is well-known. In fact, that is the basis for the cardioprotective effect of regular moderate wine consumption, which has been amply documented.
This probably doesn’t help the questioner very much, because it doesn’t really specify the level of alcohol consumption nor what constitutes a binge. However it looks like overall, moderate alcohol use in an otherwise healthy warfarin user has little effect. Geo