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Reducing Warfarin Medication Interactions
An Interrupted Time Series Evaluation
Adrianne C. Feldstein, MD, MS;
David H. Smith, RPh, MHA, PhD;
Nancy Perrin, PhD;
Xiuhai Yang, MS;
Steven R. Simon, MD, MPH;
Michael Krall, MD, MS;
Dean F. Sittig, PhD;
Diane Ditmer, PharmD;
Richard Platt, MD, MS;
Stephen B. Soumerai, ScD
Arch Intern Med. 2006;166:1009-1015.
Background Computerized decision support reduces medication errors in inpatients, but limited evidence supports its effectiveness in reducing the coprescribing of interacting medications, especially in the outpatient setting. The usefulness of academic detailing to enhance the effectiveness of medication interaction alerts also is uncertain.
Methods This study used an interrupted time series design. In a health maintenance organization with an electronic medical record, we evaluated the effectiveness of electronic medical record alerts and group academic detailing to reduce the coprescribing of warfarin and interacting medications. Participants were 239 primary care providers at 15 primary care clinics and 9910 patients taking warfarin. All 15 clinics received electronic medical record alerts for the coprescription of warfarin and 5 interacting medications: acetaminophen, nonsteroidal anti-inflammatory medications, fluconazole, metronidazole, and sulfamethoxazole. Seven clinics were randomly assigned to receive group academic detailing. The primary outcome, the interacting prescription rate (ie, the number of coprescriptions of warfarin-interacting medications per 10 000 warfarin users per month), was analyzed with segmented regression models, controlling for preintervention trends.
Results At baseline, nearly a third of patients had an interacting prescription. Coinciding with the alerts, there was an immediate and continued reduction in the warfarin-interacting medication prescription rate (from 3294.0 to 2804.2), resulting in a 14.9% relative reduction (95% confidence interval, –19.5 to –10.2) at 12 months. Group academic detailing did not enhance alert effectiveness.
Conclusions This study, using a strong and quasi-experimental design in ambulatory care, found that medication interaction alerts modestly reduced the frequency of coprescribing of interacting medications. Additional efforts will be required to further reduce rates of inappropriate prescribing of warfarin with interacting drugs.
Author Affiliations: Center for Health Research, Kaiser Permanente, Portland, Ore (Drs Feldstein, Smith, Perrin, and Sittig and Mr Yang); Northwest Permanente, Portland (Drs Feldstein, Krall, Sittig, and Ditmer); and Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, Boston, Mass (Drs Simon, Platt, and Soumerai).
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES
The Effect of Electronic Prescribing on Medication Errors and Adverse Drug Events: A Systematic Review
Ammenwerth et al.
J. Am. Med. Inform. Assoc. 2008;15:585-600.
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