Drug-drug interactions in nursing home patients

Abstract

Patients in nursing homes are often treated with many drugs concurrently (polypharmacy), which increases the risk of drug-drug interactions. The purpose of this study was to assess the incidence of such interactions in nursing home patients. The study was based on medication lists collected from all nursing home patients in Trondheim Municipality in the course of one day in 2010. Data from the medication lists was linked to the Norwegian interaction database, Druid. The study included 1241 nursing home patients. Patients used an average of 9.8 drugs regularly or as needed, with a variation of from 0 to 30. In all, 15 patients (1.2%) used drug combinations that are classified in Druid as «should not be combined», while 592 (47.7%) used combinations classified as «take precautions». There was a clear relationship between the number of drugs prescribed and the risk of interactions. The three most common drug combinations in the group «should not be combined» were warfarin and non-steroidal anti-inflammatory drugs, clopidogrel and proton pump inhibitors, and anti-Parkinson medication and dopamine antagonists. The incidence of serious drug-drug interactions among nursing home patients in Trondheim Municipality is low. Polypharmacy is widespread, and the incidence of drug interactions where precautions should be taken is high. As nursing home patients are a vulnerable group with respect to drug interactions, the risk of interactions should be carefully considered when treatment with a new drug is started.