Abstract
Eighty-four outpatients with nonrheumatic atrial fibrillation starting oral anticoagulant treatment were adminis tered warfarin (10 mg/day) for the first 2 days of treatment. Prothrombin time, expressed as International Normalized Ratio (INR), was measured on day 3 and plotted against the weekly warfarin maintenance dose, defined as the dose able to maintain INR between 2.0 and 3.0 (therapeutic range) on three consecu tive occasions, 1 week apart. The data fit a regression line (r = 0.74, p < .0001) that we use to estimate the weekly maintenance dose of other patients.
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