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Antidiarrhoeal Drugs

Drugs that stop diarrhoea by slowing the passage of the intestinal contents or regulating the action of the intestine

Common drugs

    Opioids

  • Codeine phosphate

  • Diphenoxylate

  • Loperamide

    Bulk-forming agents

  • Bran

  • Ispaghula

  • Methylcellulose

  • Sterculia

    Adsorbents

  • Kaolin

Antidiarrhoeal drugs are used to relieve diarrhoea, which is the frequent passing of loose, watery faeces. They may be used as a short-term measure to control a sudden attack of diarrhoea or long term for diarrhoea that persists due to disorders such as diverticular disease or irritable bowel syndrome. Some drugs also relieve abdominal pain associated with diarrhoea.

In most cases, an attack of diarrhoea clears up in about 48 hours and drug treatment is not normally required. Drinking plenty of fluids, but not milk, to compensate for the water that the body loses in diarrhoea is usually all that is needed. However, infants and young children are at higher risk of dehydration and may need to be given oral rehydration preparations. If an attack of diarrhoea lasts longer than 48 hours, consult your doctor. Do not give antidiarrhoeal drugs to children.

What are the types?

The main types of antidiarrhoeal drug are opioids, bulk-forming agents, and adsorbents. All types of antidiarrhoeal drug should be taken with plenty of water to prevent constipation.

Opioids

These drugs reduce the muscle contractions of the intestine. As a result, the intestine moves faeces more slowly and therefore has more time to absorb water from food residue. Opioid drugs may also help to relieve pain in the lower abdomen associated with frequent contractions of the intestinal muscle. Loperamide, although chemically similar to opioids, does not have opioid-like effects on the brain. Some opioid antidiarrhoeal drugs are available over the counter.

Bulk-forming agents

These preparations absorb water, resulting in larger and firmer stools produced at less frequent intervals. Bulk-forming agents are often given to regulate intestinal action over a long period if you have had an operation on your intestine, such as a colectomy, or if you have persistent diarrhoea due to a disorder such as diverticular disease. Since they help to regulate intestinal action, bulk-forming agents are sometimes also used as laxatives. Some types are available over the counter, others only on prescription. All types are usually supplied as granules, powder, or tablets. Do not take a bulk-forming agent when taking opioids; the combination could cause faeces to obstruct the intestine. Drink plenty of water when taking a bulk-forming agent.

Adsorbents

These substances attract and bind to irritants and other substances in the intestine, such as harmful microorganisms. As the adsorbents are moved through the intestine and excreted, the irritants are carried with them. Like bulk-forming agents, adsorbents are used to control the consistency of the faeces and to regulate intestinal action. They are usually used to treat mild diarrhoea. The adsorbent kaolin can be bought over the counter.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

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