Real-World Adherence and Relapse Risk in Mesalamine Treatment for Ulcerative Colitis: Insights from a Large Japanese...

5-Aminosalicylic acid (5-ASA, mesalamine) is the cornerstone for maintaining remission in mild-to-moderate ulcerative colitis (UC), with several formulations available. Nonadherence to mesalamine is associated with increased relapse risk; however, large-scale real-world data comparing adherence and relapse among different formulations remain limited. This study aimed to evaluate adherence and relapse risk among four 5-ASA formulations using a large Japanese healthcare database.

Using a Japanese nationwide claims database, we retrospectively analyzed UC patients who were prescribed any of four oral 5-ASA formulations - time-dependent mesalamine, pH-dependent mesalamine, multi-matrix system (MMX) mesalamine, or salazosulfapyridine - between 2008 and 2022. Adherence was assessed using the proportion of days covered (PDC), and relapse was defined as UC-related hospitalization or escalation of therapy. A Cox proportional hazards model was used to identify factors associated with relapse.

Among 13,876 eligible patients, MMX mesalamine showed the highest adherence (mean PDC: 91.6%) and the lowest relapse rate (2.9%), while salazosulfapyridine had the highest relapse rate (14.8%). In multivariate analysis, pH-dependent mesalamine (hazard ratio [HR], 0.60; 95% confidence interval [CI], 0.51-0.72) and MMX mesalamine (HR, 0.53; 95% CI, 0.35-0.78) significantly reduced relapse risk compared to time-dependent mesalamine, whereas salazosulfapyridine (HR, 1.51; 95% CI, 1.32-1.73) significantly increased relapse risk.

MMX mesalamine was associated with the highest adherence and lowest relapse rates among the four 5-ASA formulations. These findings emphasize the importance of formulation choice in UC management.