Macrogol

What it is

Macrogol, also called polyethylene glycol, is an inert long-chain polymer that is not absorbed or fermented in the gut. It works purely osmotically: it binds water molecules and carries them through to the colon, so the stool retains fluid, becomes softer and is easier to pass. It is used for constipation and is well suited to longer courses.

Used for

• Constipation

What to know while taking it

It can be taken at any time in relation to food, and it is dissolved and swallowed with fluid; drinking enough water is what makes it work at all, since the drug does nothing without the water it holds. Because it is neither absorbed nor broken down by bacteria, it produces less gas and bloating than fermented laxatives and does not typically interfere with the absorption of other medicines. Excessive or prolonged use can nevertheless shift fluid and electrolyte balance, and the effect takes a day or more to appear.

When to see a doctor

See a doctor if constipation persists despite treatment, if there is severe abdominal pain, vomiting, or a complete stop in passing stool and gas, or if diarrhoea becomes severe enough to cause weakness, dizziness or signs of dehydration.

Worth knowing

• Drink enough water