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Decreased Warfarin Effect After Initiation of High-Protein, Low-Carbohydrate Diets

at time of writing, Pharmacy Practice Resident with an Emphasis in Community Care, College of Pharmacy, The Ohio State University, Columbus, OH; now, Clinical Pharmacist, Pharmacotherapy Clinic, MedCenter Pharmacy, Marion, OH

Bella H Mehta, PharmD

Assistant Professor of Clinical Pharmacy, Division of Pharmacy Practice and Administration, College of Pharmacy, The Ohio State University

Jennifer L Rodis, PharmD

Assistant Professor of Clinical Pharmacy, Division of Pharmacy Practice and Administration, College of Pharmacy, The Ohio State University

Reprints: Dr. Rodis, College of Pharmacy, The Ohio State University, 500 W. 12th Ave., Columbus, OH 43210-1291, fax 614/292-1335, rodis.2{at}osu.edu

OBJECTIVE: To report 2 cases of decreased international normalized ratio (INR) after initiation of a high-protein, low-carbohydrate diet.

CASE SUMMARIES: Case 1. A 67-year-old white woman had been receiving warfarin for 3 years for venous thromboembolism. After initiation of a high-protein, low-carbohydrate diet, the patient required a 22.2% increase (from 45 to 57.5 mg/wk) in warfarin dose. Her INR remained in the therapeutic range on this dose for 8 weeks. When the patient stopped the high-protein, low-carbohydrate diet, a decrease back to the original warfarin dose was required to return to a therapeutic INR. Case 2. A 58-year-old white man had been receiving warfarin for 8 years for a cerebrovascular accident. Initiation of a high-protein, low-carbohydrate diet resulted in a 30% increase (from 26.25 to 37.5 mg/wk) in warfarin dose. His warfarin dose was reduced to the original dose after he stopped the high-protein, low-carbohydrate diet.

DISCUSSION: The Naranjo probability scale indicated a possible adverse effect between warfarin and high-protein diets. High-protein diets have been shown to increase serum albumin levels. This may result in more warfarin binding to serum albumin, thereby decreasing the anticoagulant effect of warfarin. The increase of albumin occurs rapidly after initiation of a high-protein diet and appears to promptly affect anticoagulation therapy with warfarin.

CONCLUSIONS: These cases indicate a significant interaction between high-protein, low-carbohydrate diets and warfarin therapy. Patients receiving warfarin therapy should be educated on and monitored for the potential interaction that occurs with warfarin therapy and high-protein, low-carbohydrate diets.

Key Words: high-protein, low-carbohydrate diet, warfarin

Published Online, March 8, 2005. www.theannals.com, DOI 10.1345/aph.1E454

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				J C. Kalvass, S. D Phinney, M. C Vernon, R. Rosedale, and E. C Westman Comment: decreased warfarin effect after initiation of high-protein, low-carbohydrate diets Ann. Pharmacother., July 1, 2005; 39(7): 1371 - 1372. [Full Text] [PDF]