More on pharmacogenomics and warfarin

Since the recent publication in AJHP of an article on the pharmacogenomic dosing of warfarin,1 two studies have been published that add to the discussion. The first was published by Eckman and colleagues,2 who presented a meta-analysis evaluating the cost-effectiveness of pharmacogenomic dosing of warfarin in patients with nonvalvular atrial fibrillation. The authors found a nonsignificant trend toward lower bleeding risk with pharmacogenomic dosing, which provided only a minimal improvement in survival rates. The cost associated with pharmacogenomic dosing exceeded $172,000 per quality-adjusted life year (QALY), which is greater than the accepted standard of $50,000 per QALY. The authors concluded that pharmacogenomic dosing was not likely to be a cost-effective strategy for patients with atrial fibrillation, except perhaps for patients who have the highest risk of bleeding. The International Warfarin Pharmacogenetics Consortium (IWPC) described a study in which clinical and genetic data from over 4000 patients were used to generate both pharmacogenomic and clinical dosage algorithms.3 The researchers then compared algorithm-generated dosages with actual maintenance dosages from a validation cohort of 1009 patients. The pharmacogenomic algorithm more accurately predicted maintenance dosages than the clinical algorithm for patients who required either ≤ 21 mg of warfarin sodium per week or ≥ 49 mg per week. Patients taking ≤ 21 mg or ≥ 49 mg per week constituted 46.2% of the cohort, and the authors concluded that pharmacogenomic dosing might be beneficial for such patients.