Potential drug-drug interactions in intensive care units of a hospital in Southern Brazil

Abstract

Drug-drug interactions are important causes of adverse reactions in health units. The high consumption of medicines in intensive care units predisposes patients to potential drug-drug interactions. This study aimed at examining the frequency and the characteristics of drug-drug interactions in intensive care units of Hospital Universitario of Universidade Estadual de Londrina. We analyzed the prescriptions of patients over 18 years, admitted from January to May 2010, who remained hospitalized for at least four days. The analysis of drug-drug interactions was carried out using the Micromedex Drug-Reax® system. The interactions were classified by severity, time required for the onset of adverse effects, mechanism of action and quality of scientific evidence. Moreover, the possible adverse events were analyzed, as well as the recommended strategies of management and monitoring. Altogether, 198 different potential drug-drug interactions were identified with the occurrence of 1242 episodes. Of these, 43% were characterized by moderate interactions, 35% major, 16% minor and 6% contraindicated. The therapeutic inefficacy was the most frequent possible adverse event (18%) and the main recommended strategy of management was the dose adjustment (35.6%). The most frequent interactions were: fentanyl + midazolam (8.6%), phenytoin + ranitidine (5.5%) and midazolam + ranitidine (4.8%). These results demonstrate the importance of drug-drug interactions as a significant adverse event in intensive care units and thus, preventive measures are required to minimize this problem.