PHARMACOEPIDEMIOLOGY AND PRESCRIPTION Application of the Pareto principle to identify and address drug-therapy safety issues Fabian Müller & Harald Dormann & Barbara Pfistermeister & Anja Sonst & Andrius Patapovas & Renate Vogler & Nina Hartmann & Bettina Plank-Kiegele & Melanie Kirchner & Thomas Bürkle & Renke Maas Received: 26 October 2013 /Accepted: 18 February 2014 /Published online: 21 March 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract Purpose Adverse drug events (ADE) and medication errors (ME) are common causes of morbidity in patients presenting at emergency departments (ED). Recognition of ADE as being drug related and prevention of ME are key to enhancing pharmacotherapy safety in ED. We assessed the applicability of the Pareto principle (∼80 % of effects result from 20 % of causes) to address locally relevant problems of drug therapy. Methods In 752 cases consecutively admitted to the nontraumatic ED of a major regional hospital, ADE, ME, contributing drugs, preventability, and detection rates of ADE by ED staff were investigated. Symptoms, errors, and drugs were sorted by frequency in order to apply the Pareto principle. Results In total, 242 ADE were observed, and 148 (61.2 %) were assessed as preventable. ADE contributed to 110 inpa- tient hospitalizations. The ten most frequent symptoms were causally involved in 88 (80.0 %) inpatient hospitalizations. Only 45 (18.6 %) ADE were recognized as drug-related problems until discharge from the ED. A limited set of 33 drugs accounted for 184 (76.0 %) ADE; ME contributed to 57 ADE. Frequency-based listing of ADE, ME, and drugs in- volved allowed identification of the most relevant problems and development of easily to implement safety measures, such as wall and pocket charts. Conclusions The Pareto principle provides a method for iden- tifying the locally most relevant ADE, ME, and involved drugs. This permits subsequent development of interventions to increase patient safety in the ED admission process that best suit local needs. Keywords Adverse drug event . Medication error . Pareto principle . Patient safety . Emergency department Introduction Adverse drug events (ADE) are a significant but frequently underestimated cause of morbidity and mortality [1–5]. Up to 14 % of hospital admissions are due to ADE [3–7], and prudent estimates from thorough post mortem investigations suggest that the lifetime risk of dying from an ADE is at least about 1:32 [8]. ADE are side effects (i.e., undesired effects) of one or more drugs, regardless of whether medication errors (ME) are involved [1]. In particular, ADE due to ME need special consideration, as ME are, in principle, avoidable. Therefore it should be possible to reduce the occurrence of ADE by preventing ME. Preventing ME and detecting ADE is especially important in the emergency department (ED), where clinical decisions Fabian Müller and Harald Dormann contributed equally in this article Electronic supplementary material The online version of this article (doi:10.1007/s00228-014-1665-2) contains supplementary material, which is available to authorized users. F. Müller (*) : B. Pfistermeister : R. Vogler : N. Hartmann : B. Plank-Kiegele : R. Maas Institute of Experimental and Clinical Pharmacology and Toxicology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstrasse 17, 91054 Erlangen, Germany e-mail: fabian.mueller@pharmakologie.med.uni-erlangen.de H. Dormann : A. Sonst Department of Emergency Medicine, Klinikum Fürth, Jakob-Henle-Strasse 1, 90766 Fürth, Germany A. Patapovas : M. Kirchner : T. Bürkle Department of Medical Informatics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Wetterkreuz 13, 91058 Erlangen, Tennenlohe, Germany R. Vogler : M. Kirchner Center for Clinical Studies (CCS), Universitätsklinikum Erlangen, Östliche Stadtmauerstrasse 30a, 91054 Erlangen, Germany Eur J Clin Pharmacol (2014) 70:727–736 DOI 10.1007/s00228-014-1665-2