Potential drug interactions in adults living in the Brazilian Amazon: A population-based case-control study, 2019

BACKGROUND: Drug interactions are important causes of adverse events. Assessments of pharmacological interactions outside healthcare services settings are scarce. OBJECTIVE: To assess the frequency and factors associated with these potential interactions in adults living in Manaus, Amazonas, Brazil. METHODS: We conducted a case-control study in 2019 with residents who had taken two or more medicines two weeks before the interview. The cases involved people with potential drug interaction, according to Micromedex™, and adults without drug interactions formed the control group. The factors associated with interaction were identified by multivariate logistic regression. RESULTS: 752 adults out of 2321 interviewed were using two or more medicines and were included. The prevalence of potential drug interactions was 30.2% (95% CI: 26.9; 33.5%). We identified 457 drug interactions, more frequently one interaction per person (49.7%), of major severity (61.9%), and with fair documentation (61.7%); three individuals were using contraindicated associations. Individuals aged 45–59 years (OR 1.88, 95% CI 1.03–3.42), using 3 or more drugs simultaneously (p-value<0.001), had higher chance of drug interactions. CONCLUSION: Drug interaction was common in among adults living in Manaus, mostly of major severity. The odds of interaction increased with age and number of concomitantly medicines.