Analysis of Potential Drug Interactions in Brazilian Mental Health Services: Prevalence and Associated Factors

Background: In the mental health field, the psychotropic polypharmacy is frequently observed, a significant risk factor for the occurrence of drug interactions. Objective: Identify potential drug interactions on the prescriptions of mental health services users and describe the associated factors. Methods: A cross-sectional study was conducted in 11 services. Sociodemographic data and information about the use of drug were obtained through interviews of users, analysis of prescriptions and medical charts, using a semi-structured questionnaire. Potential drug interactions were identified using the Micromedex® database, the association with sociodemographic characteristics and aspects related to the medicines prescribed were analyzed using the prevalence ratio. Results: The number of medicines prescribed ranged from 0 to 9, with an average of 3.38 (SD=1.76) per user, the most prescribed being haloperidol (12.3%), clonazepam (8.2%) and biperiden (7.9%). The proportion of interactions considering the number of users interviewed was 35.1%. The most frequent between potential interactions were haloperidol and fluoxetine (9.1%); haloperidol and carbamazepine (8.8%); and carbamazepine and chlorpromazine (5.9%). The highest prevalence ratio (PR) for the occurrence of potential interactions was in women (PR=1.36; 95% CI 1.08:1.71), users who had reported improper medicine use (PR=1.36; 95% CI: 1.07:1.72) and those with more than 5 prescribed medicines (PR=1.87; 95% CI: 1.49:2.33). Conclusion: Potential drug interactions were observed in more than one-third of the user’s Brazilian mental health services. The profile of interactions detected could guide the pharmacotherapeutic follow-up of priority users, and help the multidisciplinary team identify signs and symptoms that can influence the treatment of users.