Comparative efficacy of 200 mg versus 1200 mg of simethicone with 3 L polyethylene glycol electrolyte solution for afternoon colonoscopy: a randomized controlled trial.

Abstract

Background: Simethicone (SIM) can enhance bowel preparation efficiency, but the optimal dose for patients undergoing afternoon colonoscopy is still unclear. This study compares bowel preparation efficiency and adenoma detection rate (ADR) between patients receiving 3 L of polyethylene glycol electrolyte solution (PEG-ELS) with 200 mg SIM or 1200 mg SIM for afternoon colonoscopy.

Method: This prospective, randomized, and observer-blinded trial included consecutive patients undergoing colonoscopy. It compared the effects of two SIM dosages (200 mg and 1200 mg) added to a 3 L PEG-ELS regimen. The primary outcome of our study was the rate of adequate bowel preparation, as defined by all 3 segments 2 or 3 on the Boston Bowel Preparation Scale (BBPS). Secondary outcomes included the Bubble Scale (BS) score and ADR. Adverse effects related to bowel preparation were systematically administered by a trained nurse using standardized patient questionnaire.

Results: A total of 668 participants were randomly assigned to either the 200 mg group (n = 332) or 1200 mg SIM group (n = 336). There were no significant differences in baseline characteristics between the two groups. Additionally, no significant differences were observed in adequate bowel preparation rate (95.8% vs. 97.6%, P = 0.276) and ADR (22.3% vs. 25.6%, P = 0.561). Both regimens were well tolerated and accepted by participants, as assessed through a standardized patient questionnaire.

Conclusion: 200 mg versus 1200 mg of SIM in 3 L PEG-ELS for afternoon colonoscopy demonstrated no statistically significant difference in bowel cleansing quality, ADR and bowel preparation-related adverse events. This evidence supports the clinical feasibility of 200 mg simethicone as an effective alternative for optimizing colonic preparation while maintaining procedural standards.

Trial registration: This clinical trial was retrospectively registered with the Chinese Clinical Trial Registry (Registration No. ChiCTR2400089196) on 3 September 2024.