The association of age with dosage requirement for warfarin.

Two groups of patients have been studied in order to investigate the relationship between age and the effect of oral anticoagulant therapy. The first group comprised 364 patients aged 23-89 years who showed a stable anticoagulant effect on medium- or long-term warfarin therapy; in this group the elderly subjects were found to require, on average, a lower drug dose to maintain the same degree of anticoagulation. The second group comprised 130 patients aged 15-83 years who had received an initial standard oral dose of 10 mg of warfarin. No significant difference was found in the degree of anticoagulation achieved by 16 hours. Although the maintenance dose in elderly patients is somewhat lower than in younger, the same protocols can be used for the introduction of therapy.