• Stephen Vanner and Lawrence C Hookey.
• Gastrointestinal Diseases Research Unit, Kingston General Hospital, Queen's University, Ontario.
• Can. J. Gastroenterol. 2011 Dec 1; 25 (12): 663-6.

BackgroundDespite the wealth of research investigating bowel cleansing efficacy, there are very little data on the timing or frequency of bowel movements after each agent is ingested.ObjectiveTo examine the effect of each component of a three-day combined sodium picosulphate⁄magnesium citrate (PSLX) and bisacodyl regimen on the timing and frequency of bowel activity in patients undergoing colonoscopy.MethodsOutpatients booked for colonoscopy were asked to complete a diary of their bowel preparation that tracked the timing of bowel movements. Bowel preparation quality was assessed using the Ottawa Bowel Preparation Scale. Bowel activity was compared with baseline and correlated with colon cleansing. Subgroup analysis was performed examining the effect of timing of the procedure and split-dose regimens.ResultsOne hundred patients undergoing colon cleansing received bisacodyl 10 mg at 17:00 three days and two days before the day of colonoscopy. In one group, both sachets of PSLX were given the night before colonoscopy, while the second group, whose colonoscopies were scheduled after 11:00, ingested one sachet the night before and the second sachet at 06:00 on the day of colonoscopy. Patients had a mean of 1.7 bowel movements per day in the seven days before starting the cleansing regimen. Both doses of bisacodyl tablets resulted in a significant increase in the mean number of bowel movements compared with baseline (3.3⁄day first dose; 3.8⁄day second dose [P=0.03 and 0.001, respectively]). Each dose of PSLX also resulted in a significant increase in bowel movement frequency compared with baseline, with means of 4.4, 6.3 and 4.5 bowel movements after each dose. The mean time to the final bowel movement following the second sachet of PSLX was 8.9 h when taken the night before, and 3.9 h when taken the morning of the procedure. Bowel preparation quality significantly correlated with bowel frequency when total bowel movements were considered and when only the effects of bisacodyl were accounted for (P<0.01 for each).DiscussionThese data demonstrate that the addition of bisacodyl before PSLX ingestion has a significant additive effect on bowel frequency and correlates with bowel cleansing quality. The timing of the resulting bowel movements have practical implications for sleep and travel times to endoscopy suites.

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