Sodium Acid Phosphate Enema

How it works

Instilled phosphate salts exert an osmotic effect in the rectum and lower bowel, drawing in water and stimulating peristalsis to promote evacuation.

Prescribing in practice

• Phosphate enemas can cause serious fluid and electrolyte disturbances, so they should be avoided or used with great caution in renal impairment, cardiac disease and frail elderly patients.
• Careful rectal insertion is needed to avoid local trauma, and they are contraindicated where there is bowel obstruction or perforation.
• Repeated or retained administration increases the risk of phosphate absorption and electrolyte imbalance.

Monitoring

Monitor for adequate evacuation and, in vulnerable patients, watch for signs of fluid depletion or electrolyte disturbance.

Counselling the patient

• This is given rectally and usually works within a short time.
• Tell the clinician if you have kidney or heart problems before it is used.

Evidence & guidelines

Sodium acid phosphate enemas are an established means of rapid bowel evacuation, with documented cautions in UK prescribing references.