Potential drug-drug interactions in prescriptions to patients over 45 years of age in primary care, southern Brazil

• Published in: PloS one Vol. 7; no. 10; p. e47062
• Main Authors: Teixeira, Jorge Juarez Vieira, Crozatti, Márcia Terezinha Lonardoni, dos Santos, Carlos Aparecido, Romano-Lieber, Nicolina Silvana
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 10.10.2012; Public Library of Science (PLoS)
• Subjects: Adults; Age; Aged; Antidepressants; Brazil; Captopril; Cardiac arrest; Complications and side effects; Cross-Sectional Studies; Data collection; Drug Interactions; Drugs; Electronic health records; Electronic medical records; Female; Fluoxetine; Geriatrics; Health care; Hospitals; Humans; Male; Medical records; Medical research; Medicine; Middle Aged; Multivariate Analysis; Older people; Patients; Prescription drugs; Prescription Drugs - administration & dosage; Prescriptions (Drugs); Primary care; Primary Health Care; Researchers; Simvastatin; Studies; Variables; Brazil
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0047062

Few cross-sectional studies involving adults and elderly patients with major DDIs have been conducted in the primary care setting. The study aimed to investigate the prevalence of potential drug-drug interactions (DDIs) in patients treated in primary care. A cross-sectional study involving patients aged 45 years or older was conducted at 25 Basic Health Units in the city of Maringá (southern Brazil) from May to December 2010. The data were collected from prescriptions at the pharmacy of the health unit at the time of the delivery of medication to the patient. After delivery, the researcher checked the electronic medical records of the patient. A total of 827 patients were investigated (mean age: 64.1; mean number of medications: 4.4). DDIs were identified in the Micromedex® database. The prevalence of potential DDIs and major DDIs was 63.0% and 12.1%, respectively. In both the univariate and multivariate analyses, the number of drugs prescribed was significantly associated with potential DDIs, with an increasing risk from three to five drugs (OR = 4.74; 95% CI: 2.90-7.73) to six or more drugs (OR = 23.03; 95% CI: 10.42-50.91). Forty drugs accounted for 122 pairs of major DDIs, the most frequent of which involved simvastatin (23.8%), captopril/enalapril (16.4%) and fluoxetine (16.4%). This is the first large-scale study on primary care carried out in Latin America. Based on the findings, the estimated prevalence of potential DDIs was high, whereas clinically significant DDIs occurred in a smaller proportion. Exposing patients to a greater number of prescription drugs, especially three or more, proved to be a significant predictor of DDIs. Prescribers should be more aware of potential DDIs. Future studies should assess potential DDIs in primary care over a longer period of time.