Bisacodyl reduces the volume of polyethylene glycol solution required for bowel preparation

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Abstract
This study was designed to compare the efficacy and patient tolerance of standard orthograde bowel preparation using 4 liters of polyethylene glycol solution with only 2 liters of polyethylene glycol preceded by the stimulant laxative bisacodyl. Three hundred eighty-two consecutive patients undergoing outpatient colonoscopy under two surgeons over a six-month period were randomized to receive one of the two preparations. Patients were asked to record the effects of the preparation and to give it a "discomfort rating" on a scale from 1 to 5. Surgeons were blinded to the preparation used and rated the quality of bowel cleansing on a scale of 1 to 5. One hundred ninety-one patients were randomized to the 4-liter preparation and 191 to the 2-liter preparation. Ninety-three percent of patients in the 2-liter group drank all of the solution as opposed to only 66 percent of patients in the 4-liter group. Patients in the 4-liter group gave the preparation significantly lower comfort scores than those in the 2-liter group (Fisher's exact test; P = 0.0001). The quality of bowel cleansing was not significantly different between the groups (P = 0.88). A total of 6.8 percent of the 2-liter group and 9.4 percent of the 4-liter group were considered by the surgeon to have had a poor preparation (rating 4 or 5). The quality of the preparation was found to correlate with the patients' age and compliance with the preparation regimen, and was found not to correlate with presenting symptoms, pathology, or a previous colonic resection. Bowel preparation with bisacodyl and 2 liters of polyethylene glycol is more acceptable to patients than a 4-liter regimen and is equally effective in cleansing the colon.