Polypharmacy and Potential Drug–Drug Interactions in Home-Dwelling Older People – A Cross-Sectional Study

BACKGROUND: Risks associated with polypharmacy and drug–drug interactions represent a challenge in drug treatment, especially in older adults. The aim of the present study was to assess the use of prescription and non-prescription drugs and the frequency of potential drug–drug interactions in home-dwelling older individuals. METHODS: A cross-sectional study design was applied. Data were collected during preventive home visits among individuals aged ≥75 in three separate communities of Western Norway. A questionnaire, which was filled out by the individual, their next-of-kin, and the nurse performing the home visit was used for the collection of demographic and clinical data (age, sex, medication use, diagnoses, need of assistance with drug administration). Potential drug–drug interactions were identified electronically by IBM Micromedex Drug Interaction Checking. Point prevalence of potential drug–drug interactions and polypharmacy (≥5 drugs) were calculated. Binary logistic regression analyses were performed to assess factors potentially associated with polypharmacy or potential drug–drug interactions. RESULTS: Among the 233 individuals (mean age 78±3 years, 46% male) included in the study, 43% used ≥5 drugs, 3.4% ≥10 drugs, while 4.3% used no drugs. In 54% of the 197 individuals using two or more drugs, at least one potential drug–drug interaction was detected. Low-dose aspirin and simvastatin were most frequently involved in potential drug–drug interactions. In total, 25% of the individuals reported current use of drugs sold over the counter of which more than 95% were analgesic drugs. Potential drug–drug interactions involving ibuprofen were identified in nine of 11 (82%) individuals using over-the-counter ibuprofen. CONCLUSION: The study revealed a high prevalence of polypharmacy and potential drug–drug interactions with both prescription and non-prescription drugs in older home-dwelling individuals. Close monitoring of the patients at risk of drug–drug interactions, and increased awareness of the potential of over-the-counter drugs to cause drug–drug interactions, is needed.