Background: Polyethylene glycol-electrolyte solution (PEG-ELS) is routinely prescribed for bowel cleansing. Sodium phosphate (NaP) may be an effective but potentially hazardous alternative.
Aim: To investigate the safety of prescription of either agent, without being informed of the patient's medical history.
Methods: One hundred consecutive patients were randomly allocated to PEG-ELS or NaP. Prior to and after the bowel cleansing, blood was sampled for renal function and electrolytes. Patients answered questionnaires about complaints and ease of intake, and endoscopists rated the quality of bowel preparation.
Results: Eleven patients were identified with a theoretical contraindication for NaP, of whom nine should have been discovered by taking a detailed clinical history. Actually, six of them received NaP with a doubling of serum phosphate levels or hypokalaemia in four. In subjects without a contraindication to the use of NaP, hyperphosphataemia developed in 39% and hypocalcaemia in 5%. Patients tolerated NaP better and completed the preparation more often. Endoscopists rated the quality of bowel preparation equivalent, except for a better cleansed ascending colon with PEG-ELS.
Conclusions: The 11% potentially hazardous allocation to NaP and the 39% incidence of hyperphosphataemia with NaP do not justify an 'over-the-counter' prescription. Taking a detailed history and, when in doubt, using PEG-ELS will safeguard against inappropriate administration of NaP.