-Context -Unspecified Ulcerative Rectocolitis is a chronic disease that affects between 0.5 and 24.5/10 5 inhabitants in the world. National and international clinical guidelines recommend the use of aminosalicylates (including mesalazine) as first-line therapy for induction of remission of unspecified ulcerative rectocolitis, and recommend the maintenance of these agents after remission is achieved. However, multiple daily doses required for the maintenance of disease remission compromise compliance with treatment, which is very low (between 45% and 65%). Use of mesalazina in granules (2 g sachet) once daily -Pentasa ® sachets 2 g -can enhance treatment adherence, reflecting in an improvement in patients' outcomes. Objective -To evaluate the evidence on the use of mesalazine for the maintenance of remission in patients with unspecified ulcerative rectocolitis and its effectiveness when taken once versus more than once a day. From an economic standpoint, to analyze the impact of the adoption of this dosage in Brazil's public health system, considering patients' adherence to treatment. Methods -A decision tree was developed based on the Clinical Protocol and Therapeutic Guidelines for Ulcerative Colitis, published by the Ministry of Health in the lobby SAS/MS n° 861 of November 4 th, 2002 and on the algorithms published by the Associação Brasileira de Colite Ulcerativa e Doença de Crohn, aiming to get the cost-effectiveness of mesalazine once daily in granules compared with mesalazine twice daily in tablets. ResultsThe use of mesalazine increases the chances of remission induction and maintenance when compared to placebo, and higher doses are associated with greater chance of success without increasing the risk of adverse events. Conclusion -The use of a single daily dose in the maintenance of remission is effective and related to higher patient compliance when compared to the multiple daily dose regimens, with lower costs.