Comparative Effectiveness of Mebeverine and Otilonium Bromide on Health-Related Quality of Life in Patients with Irritable Bowel Syndrome: A Prospective Cohort Study.

Irritable bowel syndrome (IBS) is a common chronic gastrointestinal disorder that significantly impairs patients' quality of life. Antispasmodics such as mebeverine and otilonium bromide (OB) are commonly used as first-line therapies; however, comparative evidence regarding their effectiveness and safety profile remains limited. This study aimed to compare short-term changes in health-related quality of life and the occurrence of adverse events among IBS patients receiving mebeverine or otilonium bromide. A prospective cohort study was conducted from December 2024 to July 2025 among 110 IBS patients meeting the Rome IV criteria who received either mebeverine 200 mg or OB 40 mg twice daily for 4 weeks. The IBS-specific quality-of-life questionnaire (IBS-QOL) was interviewer-administered at baseline and after treatment (week 4). Adverse drug events were documented and classified according to the Common Terminology Criteria for Adverse Events (CTCAE). After 4 weeks, significant within-group improvements in the overall IBS-QOL score and most domain scores were observed in both treatment groups. In the unadjusted between-group analysis, the mean improvement in the overall IBS-QOL score was greater in the mebeverine group than in the otilonium bromide group (20.31 ± 13.17 vs. 14.62 ± 14.61; p = 0.034). However, treatment group was not independently associated with change in the overall IBS-QOL score after multivariable adjustment (OB vs. mebeverine: B = -4.63, 95% CI -10.28 to 1.02; p = 0.107). Nominal differences in activity interference and health worry did not remain statistically significant after Holm correction for multiple domain-level comparisons. Adverse events occurred in 9 of 110 patients (8.2%), with no significant difference between the mebeverine and otilonium bromide groups (11.7% vs. 4.0%; Fisher's exact p = 0.178). All reported events were mild. In this prospective observational cohort, both mebeverine and otilonium bromide use was associated with short-term improvement in health-related quality of life and low rates of mild adverse events. Although the unadjusted change in the overall IBS-QOL score favored mebeverine, the adjusted analysis did not establish an independent difference between the two treatments.