Factors affecting warfarin requirements. A prospective population study.

In 228 ambulatory patients receiving treatment with warfarin, there was a progressive decline in the dose required to produce an equivalent degree of anticoagulant control with increasing age from the third decade onwards. However, the relationship between age and dose was significant only in patients receiving warfarin after episodes of venous thromboembolism or because of coronary artery disease. Patient weight was also related to warfarin requirements, although it was less important a determinant than age.