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.

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. 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). Multicenter, randomized, single-blind, parallel-controlled trial. 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). 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). 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. Chinese Clinical Trial Registry: ChiCTR2300069962.