Altres ajuts: This manuscript is part of a PhD being undertaken by MGC at the Public Health Department (Departament de Pediatria, d'Obstetrícia i Ginecologia i de Medicina Preventiva) at the Universitat Autònoma de Barcelona. This work was supported by a pre-doctoral grant from Catalan Health Institute in Barcelona; by the Catalan Society of General Practitioners (CAMFiC) and by SIDIAP grant to MGC in 2015; this latter organization allowed us to explore their dataset to obtain the results. The funders had no role in the study design or data collection, analysis, and interpretation, writing of the manuscript, and decision to submit for publication.

Background: Older adults suffer from various chronic conditions which make them particularly vulnerable. The proper management of multiple drug use is therefore crucial. The aim of our study was to describe drug prescription and medication patterns in this population. Methods: A cross-sectional study in Barcelona (Spain) using electronic health records from 50 primary healthcare centres. Participants were aged 65 to 94 years, presenting multimorbidity (≥2 chronic diseases), and had been prescribed at least 1 drug for 6 months or longer during 2009. We calculated the prevalence of prescribed drugs and identified medication patterns using multiple correspondence analysis and k-means clustering. Analyses were stratified by sex and age (65-79, 80-94 years). Results: We studied 164,513 patients (66.8% women) prescribed a median of 4 drugs (interquartile range [IQR] = 3-7) in the 65-79 age-group and 6 drugs (IQR = 4-8) in the 80-94 age-group. A minimum of 45.9% of patients aged 65-79 years, and 61.8% of those aged 80-94 years, were prescribed 5 or more drugs. We identified 6 medication patterns, a non-specific one and 5 encompassing 8 anatomical groups (alimentary tract and metabolism, blood, cardiovascular, dermatological, musculo-skeletal, neurological, respiratory, and sensory organ). Conclusions: Drug prescription is widespread among the elderly. Six medication patterns were identified, 5 of which were related to one or more anatomical group, with associations among drugs from different systems. Overall, guidelines do not accurately reflect the situation of the elderly multimorbid, new strategies for managing multiple drug uses are needed to optimize prescribing in these patients.