Prevalence and factors associated with polypharmacy and potential drug interactions in adults in Manaus, Amazonas state, Brazil: a cross-sectional population-based study, 2019

To assess the prevalence and factors associated with polypharmacy and the presence of potential drug interactions in Manaus, Amazonas state, Brazil, in 2019. This was a population-based cross-sectional study conducted with adults aged ≥ 18 years. The presence of drug interactions among people on a polypharmacy regimen (≥ 5 drugs) was investigated on the Micromedex database. Prevalence ratios (PR) with 95% confidence intervals (95%CI) were calculated using Poisson regression model with robust variance, following hierarchical analysis and considering the complex sample design. Of the 2,321 participants, 2.8% (95%CI 2.1;3.6) were on polypharmacy regimen, of whom, 74.0% presented drug interactions, usually with four or more drug interactions per person (40.4%) and high severity (59.5%). Polypharmacy was higher among older adults (PR = 3.24; 95%CI 1.25;8.42), people with poor health (PR = 2.54; 95%CI 1.14;5.67), previous hospitalization (PR = 1.90; 95%CI 1.09;3.32) and multimorbidity (PR = 3.20; 95%CI 1.53;6.67). Polypharmacy was more frequent among older adults and people with medical problems, who presented more drug interactions.