Bowel cleansing efficacy for colonoscopy: prospective, randomized comparative study of same-day dosing with 1-L and 2-L PEG + ascorbate.

Polyethylene glycol (PEG) bowel preparations are effective but associated with high ingestion volume. In this study, 1-L PEG and 2-L PEG preparations were compared in a randomized, colonoscopist-blinded, single-center trial. Patients were aged > 18 years, required colonoscopy, and provided informed consent. Randomization was 1:1 to 1-L PEG or 2-L PEG, based on hospital identification number (odd or even). Preparations were administered using same-day dosing adjusted for colonoscopy start time. The primary endpoint was successful bowel preparation on the Boston Bowel Preparation Scale (BBPS) (no segment scored < 2). A total of 852 patients were randomized. In the intention-to-treat (ITT) population, significantly more patients had diabetes in the 2-L PEG arm, resulting in the creation of the modified-ITT population (mITT) that excluded diabetic patients to correct the imbalance (1-L PEG, n = 239; 2-L PEG, n = 238). In the mITT, there was no significant difference in successful cleansing between 1-L PEG and 2-L PEG (88.3 % vs. 82.4 %;  = 0.067). Excellent cleansing (BBPS 7-9; no segment < 2) was significantly improved with 1-L PEG (60.7 % vs. 50.4 %;  < 0.024), as were mean scores in the right and left colon (right: 2.47 vs. 2.30;  < 0.008; left: 2.55 vs. 2.39;  = 0.008). Adverse events were mild to moderate in intensity and none resulted in discontinuation. Rates of nausea and vomiting were significantly higher with 1-L PEG, but that did not affect successful cleansing. The lower-volume 1-L PEG was associated with higher levels of excellent bowel cleansing and greater mean segmental scores on the BBPS than 2-L PEG.