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KMID : 0869620120290040394
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Journal of Korean Society of Hospital Pharmacists
2012 Volume.29 No. 4 p.394 ~ p.404
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Evaluation of the excessive anticoagulation therapy and analysis of the clinical predictors for the return of the international normalized ratio (INR) within the therapeutic range
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Park Ka-Young
Kim Hyung-Sook
Jung Young-Mi
Choi Kyung-Suk
Lee Eun-Sook
Lee Byung-Koo
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Abstract
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Warfarin, a widely used oral anticoagulant, has a narrow therapeutic index; the side
effect is typically monitored according to the international normalized ratio (INR). While the
American College of Chest Physicians (ACCP) has proposed the guidelines for the management of excessive use of warfarin as anticoagulation, few data were published for the patient-specific factors that influence the return of the INR within the therapeutic range after the adjusted warfarin doses. Therefore, the aim of this study is to assess the treatment of excessive anticoagulation and prognostic factors that influence the return of the INR within the therapeutic range after the adjusted warfarin doses. Patients who were on warfarin therapy and were presented with an INR greater than 5.0 from Jan 1, 2007 and May 31, 2010 at Seoul National University Bundang Hospital (SNUBH), were included and observed retrospectively by reviewing electronic medical records (EMRs), such as causes of excessive anticoagulation, treatments, adjusted warfarin maintenance doses, and return of the INR within the therapeutic range after the adjusted warfarin doses. A total of 164 cases in 142 patients were analyzed. Common causes of elevated INR were excessive warfarin dose (17.8 %) and drug interaction (15.5 %). A total of 80.1 % was treated by adjusting warfarin dose, such as hold or reduction, and 67.1 % were treated appropriately according to the ACCP guidelines. Seventy-six cases found to have INR value within the therapeutic range [INR 1.7~3.3] by the adjustment and restarted warfarin therapy with adjusted dosage. However, 69 cases had INR values that were not with the range by the adjustment.
Nineteen cases were excluded by warfarin discontinuation, death or follow up loss. The variables, which were associated with INR values returned within the therapeutic range by warfarin dosage adjustment, were age (P = 0.004), maintenance doses of warfarin (P = 0.004), and reduced % of adjusted dosage of warfarin (P < 0.001). By means of a multiple logistic regression model suggested that prognostic factors are associated with maintenance dosage (odds ratio, 0.47 [Cl, 0.31 to 0.93]), and reduced % of dosage (odds ratio, 1.06 [Cl, 1.01 to 1.12]). Therefore, these observations suggested that patients who take lower weekly maintenance doses of warfarin have to monitor their INR carefully, and, if anticoagulation is excessive, appropriately reduce the doses of warfarin. Furthermore, prospective, randomized trials might help the safety and efficacy management of excessive anticoagulation.
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KEYWORD
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warfarin, excessive anticoagulation
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