CYP2C9 and VKORC1 genotype results may provide directional guidance for warfarin dosing in pediatric patients. Clinical genotyping is available through the CMH Laboratory. Approximately 50% of the variability in warfarin dose-response in adults has been associated with the variants in CYP2C9 and VKORC1 detected by this test. The test does not provide quantitative information which links a specific genotype with a precise warfarin dose and large scale studies looking at genotype and effect have not been performed; however, the results may be useful in clinical decision making when interpreted in the context of other "factors" known to influence the dose-response for warfarin (such as drug-drug interactions, patient age, drug-diet interactions, drug-disease interactions). Consultations provided by the Division of Pediatric Clinical Pharmacology and Medical Toxicology can provide such a multifactorial assessment and thus, may be beneficial.
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