Macrogol 3350

How it works

It is a high-molecular-weight inert polymer that sequesters water within the gut lumen by osmosis, increasing stool volume and softening consistency to stimulate peristalsis.

Prescribing in practice

• Contraindicated in intestinal obstruction, perforation, ileus and severe inflammatory bowel conditions such as toxic megacolon, where it must be avoided.
• Reconstitute each sachet in water and ensure adequate fluid intake; higher impaction regimens taken over a short period may cause transient abdominal distension.
• Plain macrogol 3350 sachets contain little electrolyte, so they are generally preferred over electrolyte-laden formulations for prolonged maintenance therapy.

Monitoring

Routine monitoring is not required for short-term use, but assess fluid status and response in frail or elderly patients on prolonged or high-dose regimens.

Counselling the patient

• Dissolve the powder fully in water before drinking and keep up your fluid intake.
• It may take a day or two to work; stop and seek advice if you develop severe abdominal pain or vomiting.

Evidence & guidelines

Osmotic macrogol laxatives are recommended by NICE as a first-line option for chronic constipation and for the management of faecal impaction.