This study will evaluate whether morning-only dosing of MoviPrep® (2L) for afternoon colonoscopy is as effective as a standard dosing regimen of half of the volume of MoviPrep® (1L) solution the evening prior, and half (1L) the morning of, colonoscopy. MoviPrep® is a low volume (2 liters) polyethylene glycol (PEG)-based purgative that is approved for evening-only or split (evening and morning) dosing to cleanse the colon prior to colonoscopy. Patients undergoing afternoon colonoscopies often have inferior colon cleansing. There is evidence that morning-only purgative administration of large volume PEG (4L) is safe and effective. This study will assess whether administration of a low volume PEG regimen will maintain efficacy and improve tolerance by changing a 2-day preparation procedure into a regimen that is completed in 1 day.

primary objectives

• To compare the efficacy of morning dose only MoviPrep® ("AM Dosing") where one-half of the prep is given 7 hours before colonoscopy and the second half is given 4 hours before colonoscopy, versus split dose (PM/AM) MoviPrep® ("PM/AM Dosing") where one-half of the prep is given at 6pm the night prior to colonoscopy and the second half is given 4 hours before colonoscopy.

Efficacy will be assessed based on cleansing of the entire colon, with successful cleansing defined as a score of excellent or good and unsuccessful cleansing defined as a score of fair or poor.

Secondary objectives

• To assess the tolerability of AM Dosing MoviPrep® versus PM/AM Dosing MoviPrep® based on percentage of prep completed, sleep quality/quantity, future prep choice (same prep or alternative prep described), and incidence and severity (using 11-point Likert scale) of any adverse events (i.e. nausea, vomiting, abdominal pain, bloating, light-headedness).
• To evaluate the safety of each dosing administration based on vitals with orthostatic measures (BP, pulse) on day of colonoscopy.
• To evaluate the effect of colon prep on work and productivity as measured by the degree of interference with work/productivity the day prior to colonoscopy.
• To assess difference between two dosing arms with respect to analysis of right colon cleansing, and overall adenoma detection in terms of number, size, location, histology, and morphology.
• To determine the effect of purgative dosing on procedure efficiency by measuring (a) total procedure time, (b) time from anus to cecum, and (c) withdrawal time (excluding time taken for interventions).
• To evaluate the effect of purgative dosing regimen on amount of flushing required during the procedure (0 = none, 1 = <50 ml, 2 = 50-100 ml, 3 = >100 ml).
• To validate a new grading scale for colon cleansing using the de-identified recordings of colonoscopies performed during this study.

Inclusion Criteria:

• Elective out-patients scheduled for afternoon colonoscopy (12 pm or later).

Exclusion Criteria:

• Unable or unwilling to consent
• Age < 18 years
• Pregnant
• Breast feeding
• Gastroparesis - known or suspected
• Chronic nausea or vomiting
• Bowel obstruction
• Hypomotility syndrome: pseudo-obstruction, megacolon, etc.
• Severe constipation (< 1 BM a week)
• Greater than 50% resection of colon
• Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency
• PEG allergy
• Significant psychiatric illness

out-patients scheduled for afternoon colonoscopy in the Thomas Jefferson GI group