Polypharmacy in general practice: differences between practitioners

Background. Polypharmacy, the simultaneous use of multiple drugs, is associ ated with adverse drug reactions, medication errors, and increased risk of hospitalization. When the number of concurrently used drugs totals five or more (major polypharmacy), a significant risk may be present Aim. To analyse the interpractice variation in the prevalence of major poly pharmacy among listed patients, and to identify possible predictors of majo r polypharmacy related to the practice. Method. Prescription data were retrieved from the Odense Pharmacoepidemiolo gical Database, and individuals subject to major polypharmacy were identifi ed. The age- and sex-standardized prevalence rate of major polypharmacy was calculated for each practice in the County of Funen in Denmark (n = 173), using the distribution of age and sex of the background population as a ref erence. The practice characteristics were retrieved from the Regional Healt h Insurance System. Possible predictors of major polypharmacy related to th e general practitioners (GPs) were analysed using backward stepwise linear multiple regression. Results. A six-fold variation between the practices in the prevalence of ma jor polypharmacy was found (16 to 96 per 1000 listed patients; median = 42) . Predictors related to the practice structure, workload, clinical work pro file, and prescribing profile could explain 56% of the variation. Conclusion. A substantial part of the variation in major polypharmacy betwe en practices can be explained by predictors related to practice.