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U.S. Department of Health and Human Services

Safety

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Coumadin (warfarin sodium) tablet and injection

Detailed View: Safety Labeling Changes Approved By FDA Center for Drug Evaluation and Research (CDER) – January 2010

 

Summary View

 

DOSAGE AND ADMINISTRATION

Initial Doasge

The dose of Coumadin must be individualized by monitoring the PT/INR. Not all factors causing warfarin dose variability are known. The maintenance dose needed to achieve a target PT/INR is influenced by:

  • Clinical factors including age, race, body weight, sex, concomitant medications, and comorbidities and
  • Genetic factors (CYP2C9 and VKORC1 genotypes). 
  • Select the starting dose based on the expected maintenance dose, taking into account the above factors. Routine use of loading doses is not recommended as this may increase hemorrhagic and other complications and does not offer more rapid protection against clot formation...
  • The patient’s CYP2C9 and VKORC1 genotype information, when available, can assist in selection of the starting dose...
  • Table 5: Range of Expected Therapeutic Warfarin Doses Based on CYP2C9 and VKORC1 Genotypes (new table)