The Medical Letter on Drugs and Therapeutics
Pharmacogenetic-Based Dosing of Warfarin
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Revised 6/9/08: Table 1: Acetaminophen (Tylenol*) was added.

Warfarin sodium (Coumadin, and others) and other coumarin anticoagulants prevent thrombosis, but patient response is highly variable and overanticoagulation can lead to hemorrhage.1 Genotyping patients for single nucleotide polymorphisms (SNPs) that affect coumarin metabolism and sensitivity may help clinicians estimate the therapeutic warfarin dose. The FDA has added a note to warfarin labeling recommending lowrange doses for patients with such genetic variations. Commercial tests for these variants are now available and cost about $500 per test.

CLINICAL DOSING — Traditionally, warfarin has been dosed empirically, with the initial dose based on the indication and perhaps the weight and age of the patient. By adjusting the dose based on the International Normalized Ratio (INR) response, clinicians eventually arrive at the therapeutic dose. ... more      

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Title: Pharmacogenetic-Based Dosing of Warfarin
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