• L Davydov, P A Dietz, P Lewis, M L Twichell, and J S Bertino.
• St. John's University School of Pharmacy, Jamaica, New York, USA.
• Pharmacotherapy. 2000 Oct 1; 20 (10): 1179-83.

Study ObjectiveTo determine whether unfractionated heparin is optimally dosed using published weight-based guidelines.DesignSix-month, prospective study.SettingUniversity hospital.PatientsNinety-six patients in the weight-based unfractionated heparin-dosing group 1 (WBHD1; 37 men; mean age 66.9 +/- 15.1 years; mean weight 80.1 +/- 20.6 kg) and 68 patients in the WBHD2 (25 men; mean age 68.2 +/- 15.6 years; mean weight 82.0 +/- 19.6 kg).InterventionsThe WBHD1 received a 100-U/kg intravenous bolus followed by an 18-U/kg/hour continuous intravenous infusion. After 3 months, the protocol was modified, and the WBHD2 received a 90-U/kg bolus followed by a 16-U/kg/hour continuous infusion for 3 months.Measurements And Main ResultsActivated partial thromboplastin times (aPTTs), frequency of bleeding episodes that required blood transfusions, and the number of recurrent thromboembolic events were collected from both groups after 3 months on the study. In the WBHD1, 24 hours after starting heparin, 38.5% of patients had therapeutic aPTTs, and at 48 hours, 54.3% were therapeutic. In the WBHD2, 42.6% and 51.4% of patients had therapeutic aPTTs at 24 and 48 hours, respectively. There was no statistical difference between the WBHD1 and WBHD2 in the percentage of patients with therapeutic aPTTs.ConclusionsWeight-based heparin dosing resulted in low percentages of patients with therapeutic aPTTs. The use of weight alone to dose heparin may not be adequate to optimize therapy.

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