The study adheres to STROBE guidelines. What's new?Our study reveals that Polish home-dwelling seniors consume a high number of prescription and non-prescription drugs. The factors predisposing to polypharmacy and excessive polypharmacy include multimorbidity, male sex, age 85-89 years, low level of education, and living in small or medium-sized cities. Moreover, our study provides unique data on the consumption of single pill combinations (SPCs) in Polish older patients.Since polypharmacotherapy can have negative health consequences, action must be taken in the field of complex medical and pharmaceutical care for geriatric patients. Various management strategies are available to optimize pharmacotherapy and prevent medicationrelated problems. Unfortunately, there is still limited clinical evidence for long term benefits of these interventions in elderly people. Our data can provide supportive information for the introduction of coordinated pharmaceutical care in Poland.

Background. Due to advanced age, multimorbidity and polypharmacotherapy, older patients are predisposed to drug interactions and the adverse effects of inappropriate drug combinations. Objectives.To provide up-to-date data on predisposing factors and the prevalence of possible drug interactions in the Polish geriatric population and to promote automated analysis programs as part of safe pharmacotherapy.Materials and methods. We used the Lexicomp® Drug Interactions database to assess pharmacological interactions between active substances included in all types of preparations (prescription drugs, over-thecounter drugs, vitamins, nutritional preparations, and dietary supplements) used at least once in the 2 weeks preceding the study, among 2633 home-dwelling people aged >65 years. The variables measured included age, sex, place of residence, level of education, and multimorbidity. Post-stratification was used to weigh the sample structure against the Polish population in 2017.Results. Drug interactions were identified in 81.2% of all individuals. The mean number (with 95% confidence interval (95% CI)) of all drug interactions was 4.24 (4.02-4.46), and the median value (with 1 st and 3 rd quartiles (Q1-Q3)) was 3 (1-6). At least 1 category C interaction was observed in 75.8% of all study participants, 24.3% had 1 or more category D interaction, and 4.3% had 1 or more category X interaction. The most important predisposing factor to drug interactions was multimorbidity.Conclusions. This study identified a high prevalence of potential drug interactions in the Polish geriatric population. Automated analysis systems deliver useful information on pharmacological interactions and should be promoted in the Polish healthcare community as tools to support pharmacotherapy.