Evaluation of potential prescribing errors in patients with polypharmacy: a method to improve medication safety in ambulatory care

Background Medication errors in ambulatory care are frequent and present an increased risk for adverse drug events. Polypharmacy is particularly susceptible to prescribing errors. Estimating the potential risk of such errors may lead to measures that increase patient safety. Objective The aim of this study was to evaluate potential prescribing errors that were identified by pharmacotherapy experts in patients receiving polypharmacy in ambulatory care. Methods Medication analyses of 400 patients participating in a German health insurance project and receiving polypharmacy (defined as five or more drugs) were examined. Potential prescribing errors identified were categorized into 8 main categories and 33 sub-criteria. The reliability and severity of these errors were evaluated using the Delphi method to estimate the potential risk, and a risk score was calculated. The number of responses from attending physicians receiving the results of the medication analyses was assessed. Results On average, patients took 13.4 ± standard deviation (SD) 3.6 drugs regularly. In total, 2937 potential prescribing errors were identified in 400 medical records, primarily for the criteria “indication” (29%) and “interaction” (28%). Maximum severity was found for the criterion “contraindication” ( s k = 2). The risk score was highest for the criterion “interaction” ( r k = 3.1) and lowest for “dosage” ( r k = 1.5). A total of 17% of physicians contacted replied. Conclusions A large number of potential prescribing errors were found. Medication analysis by experts combined with pharmacological consultation with the attending physicians were a valuable tool to detect potential prescribing errors and may help to improve medication safety.