Background Some adjuvants have been added to improve the quality of bowel preparation (BP) for colonoscopy and to reduce the total amount of BP solution required. However, the appropriate type of adjuvant remains unknown. We hypothesized that the addition of linaclotide, a GC-C receptor agonist approved for chronic constipation, to the low volume of PEG plus ascorbic acid (PEG-Asc), would yield better cleansing compared to the addition of senna, for which we recently reported the non-inferiority to the standard BP.

Methods Outpatients scheduled for colonoscopy were randomized to 1-L PEG-Asc plus 0.5 mg linaclotide (1L-PEG/AL) or 1-L PEG-Asc plus 24 mg senna (1L-PEG/AS) group. Boston Bowel Preparation Scale (BBPS) was used to evaluate the quality of BP. Adverse events and tolerability were surveyed using questionnaires. We also performed the stratified analysis between low- and high-risk groups for inadequate BP.

Results Between April 2022 and April 2023, 1464 patients were randomly assigned to two groups. Excluding patients who canceled colonoscopy, 720 in the 1L-PEG/AL group and 711 in the 1L-PEG/AS group were included in the PP analysis. The baseline characteristics were comparable. In the ITT and PP analysis, the 1L-PEG/AL group showed higher adequate BP rates compared with the 1L-PEG/AS group (92% vs. 86%, 94% vs 89%, P<0.01); the overall BBPS was 7.6±1.5 and 7.4±1.6, (P<0.01). Adverse events and willingness to repeat the BP were comparable between the two groups. In risk-stratified analysis, the rate of adequate BP was significantly higher in the 1L-PEG/AL group in high-risk patients (n=816) (95% vs. 85%, P<0.01), whereas comparable high rates of adequate BP rates were found between two regimens in low-risk patients (n=615) (93% vs. 94%, P=0.52).

Conclusions The linaclotide regimen was superior to the senna regimen in terms of BP efficacy without reducing tolerability. It can be a new promising option for BP, especially in patients at high risk of inadequate BP.