What is your prep of choice for patients who have had an inadequate prep with a standard HalfLytely® (2-liter polyethylene glycol–electrolyte lavage solution [PEG-ELS] with bisacodyl tablets) prep?
The best predictor of bowel prep adequacy for colonoscopy is the timing of the last dose of purgative. Dosing at least part of the prep close to the time of colonoscopy, ideally within 4-6 hours, will increase the chance of an adequate prep. This can be accomplished by splitting the dose (ie, half the night prior, half on the day of colonoscopy) or by dosing the entire prep on the day of the procedure (Aoun E et al. Gastrointest Endosc. 2005;62:213-218; Matro R et al. Am J Gastroenterol. 2010 April 12 [Epub ahead of print]). Though no published studies have formally looked at this, in my experience, patients who have inadequate cleansing with day-prior dosing regimens such as HalfLytely® usually have adequate cleansing the next time if a “day-of colonoscopy” prep is used. I recommend using a low-volume purgative approved for split dosing, if there are no contraindications to sodium phosphate. Split dose 4-L PEG-ELS given as 2 L the night prior and 2 L 5-6 hours before colonoscopy is an
