Effect of Oral Corticosteroids on Chronic Warfarin Therapy

Kathleen A. Hazlewood; Susan E. Fugate, PharmD BCPS CACP; Donald L. Harrison, PhD


The Annals of Pharmacotherapy. 2006;40(12):2101-2106. 

In This Article


A retrospective study was conducted to examine the potential drug interaction in patients receiving short-term oral corticosteroids and long-term, stable warfarin therapy in a pharmacist-run anticoagulation clinic. Medical records from January 1998 through June 2006 were reviewed for all patients actively enrolled in the clinic at the time of the study. At each visit, patients were questioned about signs of bleeding, signs and symptoms of thromboembolism, medication changes, dietary habits, alcohol use, tobacco use, warfarin dosing, adherence, and health status changes. All INR values were measured by CoaguChek or CoaguChek S devices from capillary blood samples.

The inclusion criteria were stable warfarin therapy (no change in dose for 14 days preceding pre-INR through the date of post-INR determination), short-term oral corticosteroid use (≥5 days and ≤30 days), and INR assessment both within 30 days prior to corticosteroid initiation (pre-INR) and during corticosteroid therapy or within 14 days of discontinuation (post-INR). Patients were excluded if they were prescribed any antibiotic or any medication with a documented interaction with warfarin (according to Micromedex Healthcare Series[8]) at the same time as corticosteroid initiation. The institutional review boards at Integris Baptist Medical Center and the University of Oklahoma Health Sciences Center approved this study.

The primary outcome assessed was the difference between pre- and post-INR values. Secondary endpoints included bleeding events, emergency department (ED) visits, hospitalizations, and warfarin dose modifications.

Descriptive and inferential statistics were performed. To detect a possible difference between the average pre- and post-use INR values of oral corticosteroids, a repeated measures t-test was performed. The null hypothesis was that there is no difference between the mean pre- and post-INR values of our sample. Independent samples t-tests were conducted in an effort to assess potential differences between gender and racial groups for the primary outcome. The null hypothesis for these analyses was that there is no difference between gender and ethnic groups with regard to change in INR values before and after initiation of oral corticosteroid therapy.

A χ2 test of association was used to detect potential associations between the frequency of warfarin dose modifications with regard to gender and race. The null hypothesis for these analyses was that there is no association between the frequency of dose modification and gender or racial status. Data analysis was conducted using SPSS for Windows version 11.5 (SPSS Inc., Chicago), with the a priori level of significance set at a p value of 0.05 or less.


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