Original Articles

Journal of General Internal Medicine

, Volume 2, Issue 3, pp 141-148

First online:

Initiation of warfarin therapy

Comparison of physician dosing with computer-assisted dosing
  • Richard H. WhiteAffiliated withthe Division of General Medicine, University of California, Davis, Medical Center
  • , Robyn HongAffiliated withthe Department of Pharmacy, Veterans Administration Medical Center
  • , Alan P. VenookAffiliated withthe Division of General Medicine, University of California, Davis, Medical Center
  • , Martha M. DaschbachAffiliated withthe Division of General Medicine, University of California, Davis, Medical Center
  • , William MurrayAffiliated withthe Department of Pharmacy, Veterans Administration Medical Center
  • , Dennis R. MungallAffiliated withthe Clinical Research Department, Biotrack, Inc.
  • , Robert W. ColemanAffiliated withthe Department of Pharmacy, Veterans Administration Medical Center

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Abstract

In a prospective, randomized study at two university hospitals, the authors examined how effectively housestaff physicians (n=36) managed the initiation of warfarin therapy compared with a computer-assisted dosing regimen (n=39) using the software program Warfcalc, which was managed by one of the authors. Target prothrombin time ratios were selected by the physicians. Study endpoints included: the time to reach a therapeutic prothrombin ratio, the time to reach a stable therapeutic dose, the number of patients transiently overanticoagulated, the number of bleeding complications, and the accuracy of the predicted maintenance dose, which was assessed at steady-state 10–14 days later. Computer-assisted dosing consistently outperformed the physicians: a stable therapeutic dose was achieved 3.7 days earlier (p=0.002), fewer patients were overanticoagulated (10% versus 41%), and the predicted maintenance dose was in the therapeutic range in 85% of the computer-dosed patients versus 42% of the physician group (p<0.002). For physicians who did not routinely manage warfarin therapy, computer-assisted dosing improved the accuracy of dosing and shortened the time required to achieve a stable therapeutic dose.

Key words

warfarin anticoagulation medical computing