AbstractBackgroundThis retrospective study analysed the real-world use patterns and clinical outcomes of 5-aminosalicylic acid (5-ASA) treatment in Korean patients with ulcerative colitis (UC) based on the records from national health insurance claims database (NHICD).MethodsThe records of individuals aged ≥15 years, first diagnosed as having UC between January 2009 and September 2018, were considered eligible for the study if 5-ASA was prescribed for ≥30 days within six months after the diagnosis. The data were extracted until the events of interest, patient’s death, or March 2019, whichever occurred earlier. The events of interest were defined as UC-related hospitalisation, UC-related surgery, and 5-ASA non-response, the latter corresponding to the prescription of steroids, immunosuppressants, and/or biological medications during the follow-up period. The yearly proportions of patients in each average daily dose (ADD) group, i.e., rectal monotherapy (RM), oral low dose (<2 g/day) monotherapy (OML), oral standard-to-high dose (2 g/day to ≥3 g/day) monotherapy, oral low dose combination therapy (OCL), and oral standard-to-high dose combination therapy (OCSH) group, were presented. Odds ratio for prescribing 5-ASA dose was calculated from a logistic regression model. The incidence of the events of interest was expressed per 1000 person-years (PY). Hazard ratios for 5-ASA non-response and UC-related hospitalisation in each ADD group were obtained from a Cox proportional hazard model, with OML as a reference group. Treatment adherence was expressed as a proportion of days covered (PDC) within the first 12 months from the prescription index date.ResultsThe analysis included the data of 11,338 patients (mean age 42.15 years, 59.53% of males). During a median observation period of 1,720 days, a tendency to a decrease in RM proportion was observed, along with an increase in the proportions of oral + rectal combination therapies. The odds of prescribing high-dose 5-ASA increased significantly since 2013. The proportion of OCSH increased from 18.1% in 2009 to 39.5% in 2018, whereas OML and OCL proportions decreased from 17.5% to 6.6% and from 11.6% to 6.6%, respectively. The incidence rates for non-responses and UC-related hospitalisations (per 1000 PY) were 51.16 and 13.40, respectively. Both incidence rates were significantly lower in the RM group than in the OML group, with no significant differences between the latter and other ADD groups. Mean PDC in overall population was 0.70, ranging from 0.65 to 0.76 across the ADD groups.ConclusionA tendency to a more frequent prescription of high-dose 5-ASA as combination therapy was observed in 2009-2018, along with a decrease in RM prescription frequency, which is consistent with the current guidelines.