![]() ![]() After stabilization, maintain dosing within the therapeutic range by performing periodic INRs. Determine the INR daily after the administration of the initial dose until INR results stabilize in the therapeutic range. Therefore, anticoagulation must be carefully monitored during COUMADIN therapy. Monitoring to Achieve Optimal AnticoagulationĬOUMADIN has a narrow therapeutic range (index), and its action may be affected by factors such as other drugs and dietary vitamin K. Other co-inherited VKORC1 variants may also be important determinants of warfarin dose. VKORC1–1639G>A (rs9923231) variant is used in this table. Table 1: Three Ranges of Expected Maintenance COUMADIN Daily Doses Based on CYP2C9 and VKORC1 Genotypes† † Ranges are derived from multiple published clinical studies. Patients with CYP2C9 *1/*3, *2/*2, *2/*3, and *3/*3 may require more prolonged time (>2 to 4 weeks) to achieve maximum INR effect for a given dosage regimen than patients without these CYP variants. If the patient’s CYP2C9 and/or VKORC1 genotype are known, consider these ranges in choosing the initial dose. Table 1 displays three ranges of expected maintenance COUMADIN doses observed in subgroups of patients having different combinations of CYP2C9 and VKORC1 gene variants. ĭosing Recommendations with Consideration of Genotype In general, anticoagulant therapy should be continued until the danger of thrombosis and embolism has passed. Individualize the duration of therapy for each patient. Routine use of loading doses is not recommended as this practice may increase hemorrhagic and other complications and does not offer more rapid protection against clot formation. Consider lower initial and maintenance doses for elderly and/or debilitated patients and in Asian patients. Modify this dose based on consideration of patient-specific clinical factors. Select the initial dose based on the expected maintenance dose, taking into account the above factors. Genetic factors (CYP2C9 and VKORC1 genotypes). ![]() Clinical factors including age, race, body weight, sex, concomitant medications, and comorbidities.Not all factors responsible for warfarin dose variability are known, and the initial dose is influenced by: ![]() The appropriate initial dosing of COUMADIN varies widely for different patients.
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