Macrogol (Polyethylene Glycol)

How it works

As an inert, non-absorbed polymer it sequesters water within the bowel lumen by osmosis, increasing stool water content and volume to soften faeces and promote peristalsis.

Prescribing in practice

• Do not use where intestinal obstruction, perforation, ileus or another acute surgical abdomen is suspected, as osmotic laxatives are hazardous in these settings; ensure mechanical obstruction is excluded before treating post-operative constipation.
• Dissolve each sachet in water as directed and maintain adequate fluid intake; higher regimens used for faecal impaction deliver a substantial fluid and electrolyte load.
• Use cautiously in patients with cardiovascular impairment or fluid-balance concerns when large-volume regimens are given.

Monitoring

Monitor bowel response and, when high-volume regimens are used or in frail patients, fluid balance and electrolytes.

Counselling the patient

• Mix each sachet with water as instructed and keep drinking fluids while taking it.
• Stop and seek advice if you develop abdominal pain, bloating or vomiting.

Evidence & guidelines

Macrogols are first-line osmotic laxatives with good evidence in chronic constipation and faecal impaction; the SPC contraindicates them in obstruction and perforation.