Lactulose

What it is

Lactulose is a synthetic disaccharide that human intestinal enzymes cannot break down, so it reaches the colon intact. There, gut bacteria ferment it into short-chain acids that draw water into the bowel and acidify the colonic contents, softening stool and stimulating movement. It is used for constipation, and works gradually rather than immediately.

Used for

• Constipation

What to know while taking it

It can be taken with or without food and is usually taken in the morning, since the effect appears after a delay of a day or more and timing keeps the pattern predictable. The fermentation that makes it work also produces gas, so bloating, rumbling and cramping in the first days are expected and generally settle. Enough water matters, because the osmotic effect pulls fluid into the bowel and too little intake leaves the stool hard and can lead to dehydration; heavy or prolonged use can also disturb fluid and salt balance.

When to see a doctor

See a doctor if constipation does not improve after several days of use, if diarrhoea becomes severe or persistent, or if there is severe abdominal pain, vomiting or no passage of stool and gas at all, which can indicate obstruction.

Worth knowing

• Bloating in the first days is expected
• Drink enough water