Polypharmacy and the risk of drug-drug interactions among Danish elderly - A prescription database study

Objective: To analyze the use of all subsidized prescription drugs with special attention to the elderly (greater than or equal to 70 years of age), including their use of drug combination generally accepted as carrying a risk of severe interactions. Design: Descriptive prevalence study. Setting: Odense Pharmacoepidemiological Database. Denmark. The fourth quarter of 1994. Subjects: All inhabitants in the county of Funen, Denmark. Main outcome measures: Prevalence of drug use for persons <70 and greater than or equal to 70 years of age including number of drugs used and of drug combinations. Occurrence of 35 drug combinations generally accepted as carrying a risk of severe interactions. Results: Among persons less than 70 years, 67.9% used none, 16.5% used one drug and 15.6% used tao or more prescription drugs. The corresponding prevalences for the elderly a ere 35.7%, 15.9% and 48.4%. The 26,337 elderly patients with at least two drugs used 21,293 different combinations. Of the elderly patients who had purchased greater than or equal to two drugs, 4.4% had combinations of drugs carrying a risk of severe interactions. Conclusions: Most elderly use drugs and usually several drugs concomitantly. The elderly form a heterogeneous group of drug users. Drug combinations carrying a risk of severe interactions are relatively frequent.