Miralax (PEG 3350) vs. Golytely as Bowel Preparation for Screening Colonoscopy

A major limitation to the widespread acceptance of colonoscopy as a procedure to screen for colorectal cancer is the laxative preparation. Phosphate-based preps (e.g. Fleets Phosphosoda) are now used on a limited basis because of their known association with renal injury. Polyethylene glycol (PEG) mixed with a balanced electrolyte solution (e.g. Golytely) has been used for over two decades for colon cleansing. The mixture is not very palatable due to the electrolyte additives which include sodium sulfate. To overcome the limitation of existing preps, gastroenterologists and colorectal surgeons worldwide have been using PEG powder alone (same quantity as found in Golytely prep) not mixed with electrolytes (Glycolax or Miralax) and dissolving this into 64 ounces of Gatorade. Conservatively, we estimate that 25% of colonoscopies in the US are being done with this prep. Anecdotally there have been reports (case series) that it is far more palatable and the prep is equally efficacious. The active ingredient, PEG, is not changed and therefore this is not surprising. The issue at present is that there has never been a blinded study to confirm these claims. This study will compare the efficacy of the two preps. There is no funding. The investigators will charge insurance companies for the prep - this is our current practice. The procedures will be done on healthy individuals referred for colon cancer screening and the exam will be billed to their insurance. There will be no patient honorarium. The investigators will check electrolytes to be sure patients do not develop hypokalemia with the Gatorade prep.