Efficacy and tolerability of split-dose magnesium citrate: low-volume (2 liters) polyethylene glycol vs. single- or split-dose polyethylene glycol bowel preparation for morning colonoscopy

Am J Gastroenterol. 2010 Jun;105(6):1319-26. doi: 10.1038/ajg.2010.79. Epub 2010 May 18.


Objectives: Preparation regimens for morning colonoscopy are suboptimal. The aim of this study was to test the efficacy and tolerance of a split-dose magnesium citrate-low-volume (2 liters) polyethylene glycol (PEG) regimen for morning colonoscopy.

Methods: A total of 232 patients were randomly assigned to receive 4 liters PEG (day before procedure; group 1, n=79), 2 liters PEG (day before procedure) followed by another 2 liters PEG (day of procedure; group 2, n=80), or magnesium citrate (250 ml, day before procedure) followed by 2 liters PEG (day of procedure; group 3, n=73). The quality of bowel cleansing, tolerability, and adverse effects in group 3 were compared with those in groups 1 and 2.

Results: Satisfactory bowel preparation was more frequently reported for group 3 than for group 1 (75% vs. 51%, P=0.001) and was similar to that for group 2 (75% vs. 76%, P=0.896). A significantly greater proportion of patients in group 3 graded their overall satisfaction as satisfactory compared with group 1 (43% vs. 23%, P=0.010), and the proportion was similar to that in group 2 (43% vs. 35%, P=0.133). Patients in group 3 were more willing to repeat the same preparation regimen, if necessary, than those in group 1 (93% vs. 48%, P<0.001) or group 2 (93% vs. 62%, P<0.001).

Conclusions: The split-dose magnesium citrate-low-volume (2 liters) PEG regimen was more efficient than and preferred to the conventional regimen of 4 liters of PEG, and it was equally efficient as, but, again, preferred to the split-dose (2+2 liters) regimen for morning colonoscopy.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Cathartics / administration & dosage*
  • Citric Acid / administration & dosage*
  • Colonoscopy*
  • Drug Administration Schedule
  • Female
  • Humans
  • Male
  • Middle Aged
  • Organometallic Compounds / administration & dosage*
  • Patient Acceptance of Health Care
  • Polyethylene Glycols / administration & dosage*
  • Prospective Studies
  • Single-Blind Method


  • Cathartics
  • Organometallic Compounds
  • Citric Acid
  • Polyethylene Glycols
  • magnesium citrate