Summary
Herbal remedies, considered to be both safe and effective by most consumers, may interact
with conventional drugs.Warfarin, a vitamin K antagonist originally derived from the
sweet clover plant, has a narrow therapeutic window which can be monitored using prothrombin
international normalized ratios (PT-INR). Many herbs can increase the risk for bleeding
when combined with warfarin, either by augmenting the anticoagulant effects of the
drug (with increased PT-INR levels) or through intrinsic anti-platelet properties
(without altering PT-INR levels). The increased risk for bleeding among such patients
may be difficult to predict, especially when formulas which contain many herbs are
used. Further research into herb-drug interactions is warranted, as are guidelines
for the use of herbal remedies by patients on chronic anticoagulation therapy.
Keywords
Herbs - warfarin - anticoagulation - antiplatelet - bleeding
