A randomized prospective trial comparing different regimens of oral sodium phosphate and polyethylene glycol-based lavage solution in the preparation of patients for colonoscopy

Gastrointest Endosc. 2006 Oct;64(4):544-52. doi: 10.1016/j.gie.2005.09.030.


Background: Regulatory agencies have warned clinicians regarding the risk of electrolyte abnormalities if more than two 45-mL bottles of oral sodium phosphate (NaP) solution are administered within a 24-hour period.

Objective: To compare the efficacy, safety, and tolerability of different regimens of oral NaP and polyethylene glycol (PEG).

Design: Randomized controlled trial.

Setting: Teaching hospital outpatient endoscopy clinic.

Patients: Two hundred outpatients without comorbidities who underwent routine colonoscopy.

Interventions: Two bottles of NaP, 6, 12, or 24 hours apart; or 4 L PEG.

Main outcome measurements: Bowel preparation quality, patient tolerability, and electrolyte changes.

Results: The 12- and 24-hour NaP achieved better cleansing than the 6-hour NaP or PEG. Only 8.5% and 8.3% of patients in the 24- and 12-hour NaP had poor preparations, respectively, compared with 15.6% and 23.4% in the 6-hour NaP and PEG, respectively. The poorer preparation scores with PEG were partly because of a greater amount of colonic fluid. There were no relevant electrolyte changes with PEG, whereas hypokalemia, hypocalcemia, or hyperphosphatemia developed in 5% to 57% of patients on NaP. All regimens were poorly tolerated by patients.

Limitations: The study was likely underpowered to detect small group differences in electrolytes.

Conclusions: A 24- or 12-hour NaP bowel preparation strategy was more effective than NaP 6 hours apart or PEG. PEG use is associated with more residual colonic fluid but represents an alternative to NaP in some clinical situations.

Publication types

  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Administration, Oral
  • Adolescent
  • Adult
  • Aged
  • Colon*
  • Colonoscopy*
  • Diagnosis, Differential
  • Dose-Response Relationship, Drug
  • Drug Administration Schedule
  • Female
  • Gastrointestinal Hemorrhage / etiology*
  • Humans
  • Male
  • Mass Screening*
  • Middle Aged
  • Patient Satisfaction
  • Phosphates / administration & dosage*
  • Phosphates / adverse effects
  • Polyethylene Glycols / administration & dosage*
  • Polyethylene Glycols / adverse effects
  • Prospective Studies
  • Therapeutic Irrigation*


  • Phosphates
  • Polyethylene Glycols
  • sodium phosphate