Impact of age, CYP2C9 genotype and concomitant medication on the rate of rise for prothrombin time during the first 30 days of warfarin therapy.

Objectives: To characterize the impact of several important clinical variables on the rate of anticoagulation during warfarin initiation (i.e., the first 30 days).

A prospective, randomized pilot trial of model-based warfarin dose initiation using CYP2C9 genotype and clinical data.

Background: Rapid genetic screening for cytochrome P450 (CYP) 2C9 variants may play a role in improving the efficacy and safety of warfarin in individuals with CYP2C9 variants. The feasibility of prospective CYP2C9 model-based warfarin dosing has not yet been assessed.

Objectives: To evaluate the feasibility of applying a CYP2C9 gene-based warfarin dosing model in clinical practice.

Relative impact of covariates in prescribing warfarin according to CYP2C9 genotype.

Patients on warfarin anticoagulant therapy demonstrate wide variation in maintenance dose. Patients possessing variants (*2 and *3) of the cytochrome P450 2C9 gene require reduced maintenance doses compared to those having wild-type alleles (*1). Many other clinical factors have been shown to affect warfarin dose as well.