Efficacy of morning-only compared with split-dose polyethylene glycol electrolyte solution for afternoon colonoscopy: a randomized controlled single-blind study.Matro R, Shnitser A, Spodik M, Daskalakis C, Katz L, Murtha A, Kastenberg D.Am J Gastroenterol. 2010 Sep;105(9):1954-61. Epub 2010 Apr 20. AbstractOBJECTIVES: Administering a purgative close to the time of colonoscopy is optimal for cleansing. The aim of this study was to compare the efficacy and tolerability of morning-only (AM-only) polyethylene glycol electrolyte solution (PEG-ELS) to split-dose (PM/AM) PEG-ELS for afternoon colonoscopy. METHODS: This was a single-center, prospective, randomized, investigator-blinded, non-inferiority study comparing AM-only to PM/AM PEG-ELS for afternoon outpatient colonoscopy. The primary end point was whole colon prep adequacy. Tolerance and polyp detection were secondary outcomes. RESULTS: Overall, 125 patients were randomized and 9 withdrew without taking any prep. Of 116 analyzed, 62 received AM-only prep and 54 received PM/AM prep. The whole colon prep was adequate in 92% in the AM-only group vs. 94% in the PM/AM group (95% lower confidence limit, LCL, for the difference=-11.3%, non-inferiority P=0.013), whereas the right colon prep was adequate in 93 and 92%, respectively (95% LCL=-7.8%, non-inferiority P=0.003). Polyp detection was greater, and not inferior, in the AM-only group (mean=1.57 vs. 0.94 polyps/patient, non-inferiority P=0.007). The overall incidence of adverse events was not significantly different between the two groups (P=0.273), but the AM-only group had lower incidence of abdominal pain (P=0.024). The AM-only group also had better sleep quality (P=0.007) and less interference with the previous workday (P=0.019). CONCLUSIONS: AM-only and PM/AM PEG-ELS are clinically equivalent with respect to cleansing efficacy and polyp detection. AM-only prep was associated with a lower incidence of abdominal pain, superior sleep quality, and less interference with workday before colonoscopy.