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

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.