Removal of lesions identified by colonoscopy has been shown to substantially reduce the risk of future colorectal cancer and advanced adenomas.¹ For this to happen, bowel cleansing to allow good visualisation of the colon is critical. Sub-optimal bowel preparation accounts for up to one-quarter of all colonoscopies.² This results in lower caecal intubation rates, longer procedures, decreased polyp detection and more frequent repeat colonoscopies.² The ideal preparation for a colonoscopy should be well tolerated, comfortable and safe for the patient, but also effective.

Oral sodium phosphate salts (OSPs) for bowel preparation have been used worldwide for many years for bowel cleansing prior to colonoscopy, radiological procedures and surgery. Many published randomised controlled trials and meta-analyses have demonstrated the safety and efficacy of OSP products for bowel cleansing.^3–13 OSP products are established as first-line agents in terms of efficacy and tolerability.¹⁴

OSPs are osmotic laxatives that are hypertonic relative to serum. They act by drawing water into the lumen of the gut, following an osmotic gradient. Adequate hydration during bowel preparation is critical to attenuate the fluid loss that occurs with OSP use.² Non-clinically important temporary changes in serum electrolytes include increases of serum phosphate and sodium and reductions of serum calcium and potassium.^5,15–18 This kind of medication needs to be used according to the guidance included in the special precautions and contraindications sections of their summary of product characteristics (SPC).¹⁸ OSPs are no exception. When OSPs are administered according to the SPC, in the correct dose, in the correct patient and with the correct intake and hydration measures, the electrolyte changes attributable to sodium phosphate are generally transient and clinically inconsequential.¹⁰ Reported adverse events with OSPs, as stated in the SPC, include electrolyte disturbances, volume depletion and metabolic acidosis,^{6,15,19–23,18} although many of these events have been reported in patients who were prescribed a dose of OSP solution exceeding 90ml in a 24-hour period, in patients who did not receive proper hydration during bowel preparation or in patients with a medical contraindication to the product or in whom it should be used with caution.⁶

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