Colon cleansing prior to colonoscopy is critically important to ensure effective colonoscopy for colon cancer screening, which is now widespread in North America. Currently available colon cleansing agents are limited either by potential safety concerns or significant limitations in the ability of patients to tolerate the preparation. Pico-salax has recently been introduced in Canada as an alternative agent and is being used more and more widely despite an almost complete lack of clinical data supporting efficacy and safety. This study will establish the relative efficacy and patient tolerability of this agent and its safety profile. This is a very important, practical issue which continues to challenge gastroenterologists, surgeons, internists, family doctors and thousands of their patients in Canada on a daily basis.

Anecdotal evidence suggests that the efficacy of pico-salax when used as a sole agent may not be as efficacious as oral sodium phosphate. Hence, our hypothesis is that the combination of pico-salax and bisacodyl will provide the most efficacious bowel preparation in comparison with oral sodium phosphate and pico-salax alone, while being equally if not better tolerated.

This is a randomized, investigator blinded clinical trial assessing the cleansing efficacy (using the Ottawa Bowel Preparation scale) and tolerance of three bowel cleansing regimens, two of which involve pico-salax.

Inclusion Criteria:

• Consecutive male and non-pregnant female patients
• ≥ 18 years old
• who require outpatient colonoscopy will be approached to consider participation in the study.

Exclusion Criteria:

• ileus or bowel obstruction;
• previous colorectal surgery;
• renal impairment;
• pregnancy;
• recent (<6 months) myocardial infarction or unstable angina.