Medication Errors and Potential Adverse Drug Events Among Outpatients

Presenter: Tejal K Gandhi, MD, MPH

Institution: Brigham and Women’s Hospital, Boston, MA

Co-Authors: Saul N Weingart, MD PhD, Lucian L Leape MD, Andrew C Seger RPh, Elisabeth Burdick MS, David W Bates MD MSc.

Introduction: Medication errors are common and preventable in the hospital setting and can lead to adverse drug events (ADEs). However, comparatively little is known about these events in the outpatient setting. We sought to examine the frequency and type of medication errors and potential ADEs (medication errors with potential for patient harm) that occur among outpatients.

Methods: We prospectively collected copies of prescriptions given to patients by 13 primary care providers at four general medicine practice sites in Boston, each over 4 weeks. Two sites had with electronic prescription writing (but no error checking), and two sites used handwritten prescriptions. Prescription copies were screened by a pharmacist for errors, and then verified by a two independent physicians.

Results: Among 1879 prescriptions screened, there were 158 medication errors (8.4%), and of these, 3 (2%) led to ADEs, 77 (49%) were potential ADEs, and 78 were medication errors with no potential for harm. The most common errors resulting in potential ADEs were errors in frequency (39%) and dose (27%). Of the 77 potential ADEs, one was life threatening (1%), 20 were serious (26%), and 56 (73%) were significant.

Prescriptions from computerized sites contained fewer overall medication errors (5% vs 12%, p<.0001), but did not differ in potential ADE rates (3% vs 5%, p=.14). Physician reviewers judged that advanced computerized prescribing with decision support could have prevented 77% of potential ADEs.

Discussion: We conclude that medication errors are common in the outpatient setting and often have potential to harm patients. Outpatient computerized prescribing systems with decision support may be an effective way to reduce the number of serious errors.