A Trial of Four Different Bowel Cleansing Regimens Prior to Colonoscopy
Condition: Bowel Preparation
Study type: Interventional

Summary: 
      To compare 4 commonly used bowel preparations in terms of efficacy, patient tolerability and
      safety. All these 4 bowel preparations are likely to be efficacious and safe. However, those
      with lower volume are likely to be better tolerated and completed by patients.
    

Detailed description: 
      Adequate bowel preparation is imperative for diagnostic accuracy and therapeutic safety.
      Several bowel cleansing preparations have been approved by Health Canada and are commonly
      used prior to colonoscopy. Polyethylene glycol (PEG) has been considered to be the "gold
      standard" for bowel preparation. It is a nonabsorbable solution which passes through the
      bowel without net absorption or secretion. Significant fluid and electrolyte shifts are
      therefore avoided. However, the large volume (4 liters), the salty taste and the sulphur
      smell frequently lead to poor tolerability and compliance, sometimes resulting in inadequate
      bowel preparation. Several other bowel cleansing preparations have been developed and include
      sodium phosphate (NaP), magnesium citrate, and sodium picosulphate plus magnesium oxide
      (PSMC)-containing preparations. NaP is a low volume hyperosmotic solution which draws plasma
      water into the bowel lumen to promote colonic cleansing. As a result, significant fluid and
      electrolyte shifts can occur. The advantage of the low volume is better patient tolerance
      compared to PEG. However, even in healthy individuals severe electrolyte disturbances have
      been reported when the 2 required doses are taken 12 hours apart. Therefore Health Canada has
      recommended that 2 doses of NaP be taken 24 hours apart. Patients with renal failure,
      congestive heart failure and liver failure should avoid this preparation (Grade I A). PSMC is
      a hyperosmotic saline laxative which increases intraluminal volume resulting in increased
      intestinal motility. Magnesium, a constituent of PSMC, stimulates the release of
      cholecystokinin which also stimulates intestinal motility. Since magnesium is eliminated by
      the kidney, patients with renal insufficiency or failure should also avoid this preparation.

      Many randomized controlled trials have compared the efficacy and tolerability of various
      bowel cleansing regimens. Studies comparing full-volume (4 liters) PEG with low-volume (2
      liters) PEG combined with magnesium citrate or bisacodyl have demonstrated equal efficacy of
      colonic cleansing but with improved patient tolerance. However, there is little data on how
      low volume PEG compares with NaP. The only meta-analysis of twenty nine trials on optimal
      bowel preparation concluded that NaP was more effective in bowel cleansing than 4-liter PEG
      or PSMC. However, there were only three trials comparing NaP to PSMC that met inclusion and
      exclusion criteria in this meta-analysis and the results have been conflicting. Also there
      were only three trials comparing PEG to PSMC in this meta-analysis with inconclusive data.
      Moreover, the mean number of patients per trial was small at 223, with the highest number of
      patients in a trial at 500.

      A consensus document prepared by three leading American gastrointestinal societies (American
      Society of Gastrointestinal Endoscopy, American Society of Colon and Rectal Surgeons and
      Society of American Gastrointestinal and Endoscopic Surgeons) as well as a position paper by
      the Canadian Association of Gastroenterology identified the lack of an ideal bowel
      preparation which meets all these criteria. Furthermore, the need for further studies was
      identified in the following areas:

        1. Two-liter PEG vs NaP

        2. PSMC vs NaP

      Outpatients who need to undergo routine colonoscopy will be recruited. Each patient will be
      randomly assigned to one of the four bowel preparations after they have given consent to
      participate in the study:

        1. Group 1. 4L PEG.

        2. Group 2. 2L PEG plus 4 tablets of bisacodyl.

        3. Group 3. 90 cc NaP.

        4. Group 4. PSMC plus 1 bottle of Mg-citrate (300 cc).
    

Intervention name(s): colonoscopy bowel prep
Intervention type(s): Procedure
Intervention description(s): PEG, bisacodyl, NaP, PSMC and Mg-citrate
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Diagnostic
Keywords: bowel preparation quality; colonoscopy