Sodium acid phosphate with sodium bicarbonate

How it works

The phosphate salts act osmotically within the bowel lumen to draw in water, increasing intraluminal volume and stimulating peristalsis to produce evacuation.

Prescribing in practice

• Phosphate preparations can cause significant fluid and electrolyte disturbance, so they should be avoided or used with great caution in renal impairment, cardiac disease and frail elderly patients.
• Ensure adequate hydration, as dehydration and electrolyte shifts are recognised risks.
• Avoid use where there is suspected bowel obstruction or perforation.

Monitoring

Attention to hydration status and, in at-risk patients, electrolyte monitoring is appropriate given the potential for fluid and electrolyte disturbance.

Counselling the patient

• Maintain a good fluid intake while using this preparation.
• Seek advice if you have kidney or heart problems before use.

Evidence & guidelines

Phosphate-based osmotic laxatives are an established option for bowel evacuation, with safety cautions set out in UK prescribing references.