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Potential interaction between warfarin and high dietary protein intake
Lori B Hornsby1, E Kelly Hester, Amy R Donaldson
1Department of Pharmacy Practice, Auburn University Harrison School of Pharmacy, Auburn, AL, USA.
Pharmacotherapy
|March 28, 2008
Summary
High-protein diets may reduce warfarin effectiveness, requiring dosage increases. Patients on warfarin should monitor their International Normalized Ratio (INR) closely when changing to a high-protein diet.
Area of Science:
- Pharmacology
- Nutrition Science
- Internal Medicine
Background:
- Warfarin is a common anticoagulant medication used to prevent blood clots.
- Maintaining a stable International Normalized Ratio (INR) is crucial for warfarin therapy efficacy and safety.
- Aortic valve replacement patients often require long-term anticoagulation therapy with warfarin.
Observation:
- A patient on a stable warfarin regimen (95 mg/week) experienced subtherapeutic INRs after initiating a high-protein diet.
- The warfarin dosage had to be increased by 16% to maintain therapeutic INRs during the diet.
- Upon discontinuing the diet, INR levels rose, necessitating dosage reductions to the original maintenance level.
Findings:
- This case, along with two prior reports, suggests a potential drug-food interaction between warfarin and high-protein diets.
- The proposed mechanism involves increased dietary protein potentially enhancing cytochrome P450 activity, leading to accelerated warfarin metabolism.
- Altered dietary protein intake can influence drug metabolism, as evidenced by animal and human studies.
Implications:
- Patients and healthcare providers should be aware of the potential for high-protein diets to decrease warfarin's anticoagulant effect.
- Close INR monitoring is recommended for patients on warfarin who adopt high-protein diets.
- This interaction highlights the importance of considering dietary factors in medication management, especially for anticoagulation.
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