Efficacy and safety of Shouhui Tongbian Capsules, a traditional Chinese medicine, combined with 2L polyethylene glycol for bowel preparation before colonoscopy: a multicenter, randomized, single-blind, parallel-controlled clinical trial

Background: High-volume polyethylene glycol (PEG) solutions are commonly used for bowel preparation but are often poorly tolerated, reducing patient compliance. Shouhui Tongbian Capsules (SHTBC), a traditional Chinese medicine known to promote gastrointestinal motility, may offer an alternative approach. However, its role in bowel preparation remains unclear. Objectives: To evaluate the efficacy, safety, and tolerability of a novel bowel preparation regimen combining SHTBC with low-volume PEG (2L) compared to conventional high-volume PEG (3L). Design: Multicenter, randomized, single-blind, parallel-controlled trial. Methods: A total of 404 participants scheduled for colonoscopy across 34 medical centers in China were randomized into two groups: the experimental group (SHTBC + 2L PEG, n  = 202) and the control group (3L PEG, n  = 202). Bowel preparation quality was assessed using the Boston Bowel Preparation Scale (BBPS), with successful cleansing defined as a total BBPS score ⩾6. The secondary outcomes included time to adequate bowel movement, number of bowel movements, patient tolerance, acceptance, and incidence of adverse drug reactions (ADRs). Results: The success rate of bowel preparation was comparable between groups ( p  = 0.7454). The experimental group had a slightly longer time to first adequate bowel movement on the day of colonoscopy ( p  = 0.0013) but experienced fewer bowel movements the day before ( p  < 0.0001). The experimental group reported significantly fewer ADRs ( p  = 0.0311) and better tolerance, including reduced bloating, nausea, and sleep disturbance ( p  < 0.01 for all). Patient acceptance was higher in the experimental group (92.89% vs 88.32%), although the difference was not statistically significant ( p  = 0.4170). Conclusion: SHTBC combined with 2L PEG is a safe, effective, and better-tolerated alternative to 3L PEG for bowel preparation before colonoscopy, offering a promising strategy to improve patient compliance. Trial registration: Chinese Clinical Trial Registry: ChiCTR2300069962.