Glycerol with magnesium sulfate and phenol

How it works

Magnesium sulfate and glycerol act as osmotic agents drawing water into the bowel lumen while glycerol also lubricates, together promoting rectal evacuation; phenol provides a mild local effect.

Prescribing in practice

• It is contraindicated in acute gastrointestinal conditions such as intestinal obstruction, acute inflammatory bowel disease and undiagnosed abdominal pain or rectal bleeding.
• Magnesium can be absorbed from the bowel, so caution is needed in renal impairment and the elderly where magnesium accumulation may occur.
• It is intended for occasional bowel evacuation rather than long-term management of constipation.

Monitoring

Routine monitoring is not generally required, but consider electrolyte status with repeated use or in renal impairment given the magnesium content.

Counselling the patient

• This enema is given to clear the lower bowel and usually works within a short time.
• Tell the team if you have kidney problems or significant abdominal pain before it is used.

Evidence & guidelines

Compound osmotic rectal enemas are an established option for bowel evacuation where a rapid rectal effect is required.