Low-volume PEG plus ascorbic acid versus high-volume PEG as bowel preparation for colonoscopy

OBJECTIVE: High volumes of polyethylene glycol (PEG)-based solutions as bowel preparation for colonoscopy are effective, but often poorly tolerated. To compare a 2 l PEG-based solution combined with ascorbic acid (PEG + Asc) with 4 l PEG-based solution (PEG). METHODS: In a single blind, quasi-randomized, prospective study, 350 patients undergoing colonoscopy received 2 l of PEG + Asc or 4 l of PEG. For morning procedures, the total dose of PEG + Asc was taken the evening before, for afternoon colonoscopies, PEG + Asc was given as a split dose. The 4 l PEG preparation was given as a split dose. Efficacy of preparation was scored on a five-point scale in three different colon segments. Patients' experiences were evaluated using a questionnaire. RESULTS: From 307 patients (149 PEG + Asc, 158 PEG), results were available. Successful colon cleansing was achieved in 90.6% in the PEG + Asc group compared to 96% in the PEG group (not significant). In patients prepared with PEG + Asc, bowel cleansing was worse when patients underwent colonoscopy in the morning, compared to afternoon procedures. Side-effects and patients' experiences were similar in the PEG + Asc and PEG group. CONCLUSIONS: Low-volume PEG + ascorbic acid has comparable efficacy and tolerability as high-volume PEG solution. The cleansing results were worse if patients received the full dose PEG + Asc the evening before the procedure compared to the split dose. Our data support the administration of PEG + Asc as a split dose before the procedure.