© 2003 Schattauer GmbH, Stuttgart 260 Introduction The indications for long-term therapy with coumarin anticoag- ulants have broadened considerably over the past few decades. Although this therapy has been made safer by improved labora- tory testing and establishment of clear therapeutic ranges for intensity, a significant risk of complications persists and the management of patients taking anticoagulants remains subopti- mal. In various studies of patients taking coumarin anticoagu- lants, the international normalised ratio (INR), used to monitor the intensity of anticoagulation, is outside the prescribed thera- peutic range 10% to 70% of the time (1). This is undesirable Comparison of control and stability of oral anticoagulant therapy using acenocoumarol versus phenprocoumon Stephan D. Fihn 1, 2 ,Alain A. P. Gadisseur 4 , Edwin Pasterkamp 3 , Felix J. M. van der Meer 4 , W. G. Mimi Breukink-Engbers 5 , Lya M. Geven-Boere 6 , Erik van Meegen 7 , Hanneke de Vries- Goldschmeding 8 , Irma Antheunissen-Anneveld 9 ,Annelies R. van’t Hoff 10 , Derk Harderman 11 , Margriet Smink 12 , Frits R. Rosendaal 3, 4 1 Northwest Health Services Research Center of Excellence,Veteran Affairs Puget Sound Health Care System, the 2 Department of Medicine of the University of Washington, Seattle,Washington, USA, 3 Department of Clinical Epidemiology and Hemostasis and 4 Thrombosis Center of the Leiden University Medical Center, 5 Oostgelderland Anticoagulation Clinic, Lichtenvoorde; 6 Leeuwarden Anticoagulation Clinic; 7 Anticoagulation Clinic of the Hague; 8 Thrombosis Center of the Utrecht Division of the Dutch Red Cross, 9 Schiedam Anticoagulation Clinic, 10 Anticoagulation Clinic of Midden-Brabant, 11 Anticoagulation Clinic Zuid-West Friesland, 12 Anticoagulation Service Alkmaar,The Netherlands Thromb Haemost 2003; 90: 260–6 phenprocoumon were within the therapeutic range 50% of the time compared with 43% for acenocoumarol (OR 1.32, 95% CI 1.24-1.41). Moreover, patients on phenprocoumon required 15% fewer monitoring visits and had more stable INR values. These observations were consistent for all six clinics. There were also sizable differences between the clinics with respect to control and stability of anticoagulation that were stable from year-to-year and were unrelated to the drug used. With its longer half-life of three to five days, phenprocoumon produces more stable anticoagulation than acenocoumarol and should generally be the drug of choice when these are the avail- able choices. The differences observed among clinics suggest that certain clinics employ policies and practices resulting in better control of anticoagulation. Keywords Anticoagulation, international normalised ratio, phenprocou- mon, acenocoumarol Summary Variability in the control of oral anticoagulant therapy has been associated with a heightened risk of complications. We com- pared control of anticoagulation between two commonly used coumarins, phenprocoumon and acenocoumarol, and among anticoagulation clinics. All qualifying patients were managed at six regional anticoagu- lation clinics in the Netherlands. This retrospective cohort study compiled data during a three- year period from a computerised dosing and management system. Anticoagulation control was expressed as the percent of time within the therapeutic range and stability expressed as the time- weighted variance in the international normalised ratio (INR). Data were available for 22,178 patients of whom 72% were treated with acenocoumarol. INRs of patients who received Correspondence to: Dr. Fihn Northwest VA Health Services Research & Development Center of Excellence VA Puget Sound Health Care System (152) 1660 S. Columbian Way Seattle,WA 98108. USA E-mail: sfihn@u.washington.edu Received October 21, 2002 Accepted after revision March 19, 2003 Financial support: This work was supported by a visitors grant from the Nederlandse Organizatsie voor Wetenschappelijk Onderzoek. DOI: 10.1160/TH02-10-0179 Blood Coagulation, Fibrinolysis and Cellular Haemostasis For personal or educational use only. No other uses without permission. All rights reserved. Downloaded from www.thrombosis-online.com on 2018-03-24 | ID: 1001066444 | IP: 54.70.40.11