RATIONALE, AIMS AND OBJECTIVES: Literature have showed inconclusive or contradictory results regarding medication review services effectiveness in optimizing process indicators. Thus, this study aimed to evaluate the process indicators of a medication review service between pharmacists and physicians. METHOD: This quasi-experimental study was conducted between March 2013 and February 2014 with patients who were receiving care in a medication review service in a teaching hospital in northeastern Brazil. The main process indicators were number of pharmaceutical consultations; identification and resolution of drug-related problems (DRP) and pharmaceutical interventions that were classified according to type and degree of acceptance. Descriptive statistics were used to report data. The statistical significance of the association between variables was evaluated using the Mantel-Haenszel chi-square test. The 95% confidence interval was considered, and differences were deemed statistically significant if P ≤ .05. RESULTS: A total of 146 patients attended the medication review service. The number of consultations per patient ranged from one to five (2.1 ± 1.1). The service identified 366 DRP, most of which were indication (67.5%). Patients who had four to five pharmaceutical consultations were 1.14 times more likely to have their DRP identified (χ2 = 33.83, P < .0001). Of the DRP identified, 183 (42.33%) were resolved. Patients who had between one and two pharmaceutical consultations were 1.22 times more likely not to have their DRP resolved compared with the group with more than three consultations (χ2 = 3.44, P < .05). Of the 173 pharmaceutical interventions made to the medical students and physicians, the majority (98.7%) was accepted. CONCLUSION: The collaborative medication review service optimized the process indicators. Drug-related problems identification and resolution required more than three pharmaceutical consultations. Most of the pharmaceutical interventions were accepted by prescribers. Thus, collaborative medication review services may be fundamental to the construction of more effective and safe health systems.