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

Drug interactions are important causes of adverse events. Assessments of pharmacological interactions outside healthcare services settings are scarce.

To assess the frequency and factors associated with these potential interactions in adults living in Manaus, Amazonas, Brazil.

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.

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.

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.