Compare Polyethylene Glycol and Sodium Picosulfate Alone or Combined

Sodium picosulfate/magnesium citrate (SPMC) is generally better tolerated than PEG, its cleansing effect remains uncertain. While most studies showed SPMC was non-inferior to PEG, some studies reported that SPMC was less effective than PEG. To improve the bowel cleansing effect of SPMC, splitting the dose by using one sachet the evening before colonoscopy and the other sachet 4 to 5 hours before colonoscopy in the morning, has been proposed.Adding bisacodyl to the regimen also has been shown to be helpful. Some side effects, such as hyponatremia, dehydration and sleep disturbance, were reported to be more commonly associated with SPMC than with PEG. To enhance the efficacy and reduce the side effects, two studies have evaluated the combination of SPMC and PEG, with conflicting results.The effect of combining PEG and SPMC should be best appreciated with head-to-head comparison with PEG and SPMC alone at the same time. Therefore we designed this head-to-head comparison study for 2 L PEG, 1L PEG plus one sachet of SPMC and 2 sachet of SPMC, all with split-dose and the addition of 10 ml bisacodyl. Our hypothesis is the bowel cleansing effect of the combination regimen was not inferior to PEG alone. The tolerability, acceptability and side effects of the 3 regimen will also be evaluated. Patients will be randomly assigned to either PEG, PEG plus SPMC or SPMC group, in a 1:1:1 ratio using a computer-generated sequence. The treatment allocation will be concealed and revealed by non-research medical personnel at the screening visit.