Evaluation of three dosage-prediction methods for initial in-hospital stabilization of warfarin therapy

Abstract

Three dosage-prediction methods for initial in-hospital stabilization of warfarin therapy were evaluated. Adult inpatients who had received warfarin sodium 10 mg daily for less than three days were eligible for the study. After receiving their third warfarin dose, patients were randomly assigned to have their warfarin dosages adjusted using one of three dosage-prediction methods: by analog computer (n = 31), linear regression (n = 22), or empiric dosing by the physician (n = 34). A prothrombin time (PT) ratio (patient PT divided by control PT) between 1.3 and 2.5 was considered to be in the therapeutic range. For patients who achieved a stable PT ratio (defined as a PT ratio between 1.3 and 2.5 that varied by less than 0.05 on two consecutive days or by less than 0.1 on three consecutive days without a dosage change) before discharge, the number of days (time to stabilization) from administration of the first warfarin dose to achievement of the warfarin dosage that produced a stable PT ratio (stabilization dosage) was compared. A total of 54 patients met the study criteria for a stable PT ratio before hospital discharge (analog computer, n = 20; linear regression, n = 15; empiric dosing, n = 19). The mean times to stabilization were 6.8 days in the analog-computer group, 7.3 days in the linear-regression group, and 8.4 days in the empiric-dosing group; these times were not significantly different. All 20 stabilized patients in the analog-computer group achieved a stable PT ratio by the fourth dosage prediction.(ABSTRACT TRUNCATED AT 250 WORDS)