Macrogol (Polyethylene Glycol)

How it works

Macrogol is an inert polymer that binds water osmotically and is not absorbed or metabolised, so it retains fluid within the bowel to increase stool volume and soften it, stimulating peristalsis and bowel evacuation.

Prescribing in practice

• It is contraindicated in intestinal obstruction or perforation, ileus and severe inflammatory bowel conditions such as toxic megacolon, where stimulating bowel transit is dangerous.
• Higher-volume regimens used for faecal impaction can cause fluid and electrolyte shifts, so caution is needed in frail, elderly or cardiovascularly impaired patients and adequate hydration is important.
• Each sachet must be dissolved in the recommended volume of water before drinking to ensure the osmotic balance is correct.

Monitoring

Routine monitoring is not usually required, but consider fluid and electrolyte status when high doses are used for impaction or in vulnerable patients.

Counselling the patient

• Dissolve each sachet fully in water before drinking and keep up your overall fluid intake.
• When used to clear a blockage of hardened stool you may need to drink several sachets over the day as directed.

Evidence & guidelines

NICE recommends macrogols as a first-line osmotic laxative for chronic constipation and for the treatment of faecal impaction.