What would be the best choice for managing a patient on warfarin with two CYP2C9 decreased-function alleles?

Managing a patient on warfarin with two CYP2C9 decreased-function alleles requires a careful approach to dosing. Patients carrying decreased-function alleles of the CYP2C9 gene have reduced metabolic activity, leading to slower clearance of warfarin from the body. This can predispose them to an increased risk of bleeding due to elevated levels of the anticoagulant.

In this specific case, the best choice is to reduce the warfarin dose. By lowering the dose, the medical provider can help ensure that the therapeutic range is maintained without causing excessive anticoagulation, thereby minimizing the risk of complications such as bleeding events. In patients with identified decreased-function alleles, pharmacogenetic testing is crucial as it can guide the adjustment of warfarin dosing to achieve optimal treatment outcomes aligned with their genetic metabolism capacity.

Maintaining the current dose or increasing it could lead to dangerous elevations in INR (International Normalized Ratio), increasing the likelihood of adverse events. Discontinuing therapy is generally not warranted unless there are other compelling reasons, such as a high risk of bleeding that cannot be managed by dose adjustments. Therefore, reducing the warfarin dosage is the most appropriate and safest management strategy in this scenario.