A client with a high 2D6 polymorphism requires warfarin. What dosage is likely required?

Individuals with certain polymorphisms in the CYP2D6 enzyme can have altered drug metabolism. The specific polymorphism in question can lead to either ultra-rapid or poor metabolism of drugs that are substrates of this enzyme. In the case of warfarin, which is primarily metabolized by CYP2C9 and VKORC1 but not significantly by CYP2D6, the relevance of CYP2D6 polymorphism still pertains to drug interactions and how other medications metabolized by CYP2D6 may affect the overall anticoagulant effect.

When a client has a high CYP2D6 polymorphism—specifically, if they are an ultra-rapid metabolizer—this could lead to an increased requirement for warfarin to achieve the desired anticoagulation effect. Ultra-rapid metabolizers may eliminate medications more quickly and thus may require higher doses to maintain therapeutic efficacy, as the drug is metabolized and cleared from the body faster than in individuals with normal metabolic function.

Therefore, this client is likely to require a higher dose of warfarin to achieve the necessary anticoagulation levels, making this the correct understanding of their situation.