Efficacy and safety of sodium phosphate powder for bowel cleansing in patients aged 50–70 years: a randomised, multicentre, single-blind trial

High-volume polyethylene glycol (PEG) offers a safe bowel preparation but is often poorly tolerated, whereas low-volume hyperosmotic agents like sodium phosphate (NaP) may improve tolerability but pose safety risks from fluid and electrolyte shifts. We therefore aimed to compare a 1.6-L NaP powder regimen with a standard 4.0-L PEG regimen for bowel preparation efficacy, patient compliance, tolerability, safety in individuals aged 50–70. In this multicenter, randomized, single-blind, non-inferiority trial, patients aged 50 to 70 years were randomly assigned to NaP group and PEG group. The primary outcome was the rate of adequate bowel preparation assessed using the Boston Bowel Preparation Scale (BBPS). Between November 2023 and January 2025, 728 patients from 8 tertiary hospitals in China were recruited and 713 patients were randomly assigned to either the NaP group (n = 362) or the PEG group (n = 351). The adequate preparations rate (BBPS ≥ 6 score) was 93.37% in the NaP group and 93.73% in the PEG group (absolute difference − 0.36%, 95% CI -3.97% to 3.24%; Pnon−inferiority < 0.001). The incidence of adverse events, withdrawal time, cecal intubation rate, polyp detection rate, and adenoma detection rate showed no statistical difference. The NaP group exhibited more pronounced changes in blood electrolytes than the PEG group, including potassium (-0.28 ± 0.39 vs. -0.04 ± 0.36, P < 0.001), calcium (-0.11 ± 0.14 vs. -0.04 ± 0.12, P < 0.001), and sodium (1.03 ± 2.79 vs. 0.44 ± 2.62, P < 0.001). However, the alterations in serum creatinine were comparable between the two groups (-0.88 ± 8.57 vs. -1.00 ± 9.58, P = 0.152). No serious adverse events occurred between two groups. Notably, patients in the NaP group reported significantly higher satisfaction scores than those in the PEG group (8.74 ± 1.28 vs. 7.09 ± 1.58, P < 0.001). NaP is an effective low-volume purgative that is non-inferior to PEG in Chinese individuals aged 50–70 years with normal renal function. NaP results in greater patient satisfaction. The study was approved by the research ethic boards from all sites and was retrospectively registered in the Chinese Clinical Trial Registry (ChiCTR) (registration number: ChiCTR2500095664) on January 10, 2025.