PHARMACOEPIDEMIOLOGY AND PRESCRIPTION Inappropriate prescribing for the elderly—a modern epidemic? Gunhild Nyborg & Jørund Straand & Mette Brekke Received: 5 October 2011 / Accepted: 13 January 2012 # Springer-Verlag 2012 Abstract Purpose The elderly often use several drugs on a regular basis and are especially at risk for drug-related harm from side effects and interactions. The aim of this study was to explore the overall prevalence of and predictors for poten- tially inappropriate medication use among Norwegian elder- ly outpatients. Methods A pharmaco-epidemiological retrospective cross- sectional survey was undertaken based on data from the Norwegian Prescription Database. Prescriptions from all doctors in Norway, dispensed by pharmacies to home- dwelling elderly ≥70 years in 2008, were included for a total of 11,491,065 prescriptions from 24,540 prescribers to 445,900 individuals (88.3% of the Norwegian population in this age group, 58.9% females). We applied a list of criteria for pharmacological inappropriateness for elderly people (the NORGEP criteria) to determine the prevalence of potentially inappropriate medications (PIMs) and applied a multiple logistic regression model to identify predictors. Results According to our criteria, 34.8% of the study pop- ulation (28.5% of the men, 39.3% of the women) was exposed to at least one PIM. Of these, 59.9% represented psychoactive substances. The odds of receiving potentially harmful prescriptions increased with the number of prescrib- ers (OR 3.52, 99% CI 3.44–3.60 for those with ≥5 compared to those with 1 or 2 prescribers). Twenty percent were prescribed more than 10 medications; among these two- thirds had at least one PIM. Adjusted for differences in age distribution and the number of prescribers involved, women were more frequently exposed to PIMs than men, with an odds ratio of 1.60 (99% CI 1.58–1.64). Conclusions About one-third of the elderly Norwegian pop- ulation is exposed to potentially inappropriate medications, and elderly females are at particular risk. Keywords Drug safety . Elderly . Explicit criteria . Inappropriate prescribing . NORGEP criteria . Norway Introduction Modern pharmacotherapy can be a double-edged sword. While many have their lives prolonged and enjoy a better quality of life, there is always a risk of adverse drug reac- tions (ADRs). At present there is reason to characterize ADRs as a threat to public health: an estimated 5,000 hospital beds in England are at any time occupied by patients admitted for ADRs [1]. A Swedish study with data from 2001 estimated that 3% of deaths in the general pop- ulation were caused by ADRs [2]. In a meta-analysis from 1998, Lazarou et al. found the incidence of fatal ADRs in the USA to be 0.32%, making ADRs the fourth to sixth most common cause of death [3], and in a study from a Norwegian department of internal medicine, every fifth death was considered to be at least partly caused by ADRs, with the oldest patients at particular risk [4]. The risk of ADRs increases with the number of drugs taken [5]. Older people have a higher prevalence of comor- bidities, and only a few decades after the first pharmaceuti- cal discoveries many elderly now use a substantial and still increasing number of drugs on a regular basis [6]. In 2008, persons 70 years or older represented 15% of the drug users in Norway but received 35% of the total amount of drugs dispensed on prescription [7]. The question is whether this G. Nyborg (*) : J. Straand : M. Brekke Department of General Practice/Family Medicine, Institute of Health and Society, University of Oslo, Oslo, Norway e-mail: gunhild.nyborg@medisin.uio.no Eur J Clin Pharmacol DOI 10.1007/s00228-012-1223-8