A simple technique for predicting maintenance dosage of warfarin--is it better than empirical dosing?

In a prospective, randomised trial the clinical utility of a predictive warfarin maintenance dosing technique was compared with the more commonly employed empirical dosing method. A preliminary study in 35 patients established the applied technique for predicting the maintenance dosage of warfarin from the prothrombin activity on Day 4 of initial standardised warfarin administration. Forty-three patients admitted with venous thrombotic disease were investigated. All received the same loading dose of warfarin (10 mg daily) until the prothrombin percentage activity (Normotest) was less than 25%. Significantly more patients were correctly stabilised when warfarin doses were based on prediction than when they were empirically adjusted (86% vs 50%). Also, the median number of days to achieve stable anticoagulation was lower (8 vs 11 days). It is concluded that this simple predictive technique to determine the maintenance dosage of warfarin is superior to empirical dosing.