ABSTRACT: INTRODUCTION:Conventional pharmaceutical interventions for inflammatory bowel disease (IBD) provide limited disease/symptom control and are associated with an increased risk of adverse events (AEs). These limitations increase patient morbidity, medical resource utilization (MRU), and costs. METHODS:The IQVIA™ Real-World Data Adjudicated Claims-US database was leveraged to identify adult patients (>?18 years) with Crohn's disease (Crohn's) or ulcerative colitis (UC), who were new and chronic users (??60 days) of oral corticosteroids (OCS), immunosuppressants (IS), anti-tumor necrosis factor agents (anti-TNF) or combinations thereof. Using aminosalicylate-treated patients as a reference, we compared AE incidence, MRU, and medical costs across drug classes. RESULTS:The analysis included 30,676 patients (Crohn's: n?=?14,528; UC: n? = 16,148). OCS monotherapy was the strongest predictor of any AE occurring [Crohn's: hazard ratio 1.62 (1.51-1.73); UC: hazard ratio 1.57 (1.49-1.66)]. A similar pattern was observed for severe infection and bone-related conditions. Patients with UC or Crohn's receiving OCS or IS plus OCS were more likely to have emergency department visits, IBD-related hospitalizations/visits/procedures, and gastrointestinal surgery than were patients receiving other therapies. Annualized total medical costs (pharmacy plus hospital service costs) were greatest for anti-TNF plus IS or anti-TNF therapy in both Crohn's and UC. Annualized medical service costs (excluding IBD drug costs) were highest for patients initiating OCS-containing therapies [Crohn's: OCS, $27,041 (24,882-29,200) and OCS plus IS, $23,332 (19,889-26,775); UC: OCS, $19,659 (17,977-21,340)]. CONCLUSION:Although biologic therapies have higher pharmacy costs, treatment decisions should consider the increased AE risks and long-term MRU costs associated with chronic use of OCS-containing therapies. FUNDING:This study was funded by F. Hoffmann-La Roche Ltd. The journal's Rapid Service Fee and Open Access publication were paid for by ApotheCom on behalf of Genentech, a member of the Roche group who funded the study.