Antidiarrhoeal Medicines for Acute Diarrhoea

What is acute diarrhoea?

Acute diarrhoea is diarrhoea which starts suddenly and lasts for less than two weeks. There are a number of causes of acute diarrhoea:

  • Infection of the gut is the common cause. This is called acute infectious diarrhoea. Many bacteria, viruses, and other germs can cause diarrhoea. Sometimes the germs come from infected food (food poisoning). Infected water is a cause in some countries. Sometimes it is just “one of those germs going about”. Viruses are easily spread from one person to another by close contact, or when an infected person prepares food for others.
  • Other causes are uncommon and include: drinking lots of beer, side-effects from some medicines, and anxiety.
  • Gut disorders that cause chronic (persistent) diarrhoea may be mistaken for acute diarrhoea when they first begin – for example, diarrhoea caused by ulcerative colitis.

What are antidiarrhoeal medicines?

Antidiarrhoeal medicines are used to reduce the number of trips that you need to make to the toilet when you have diarrhoea. Two types of antidiarrhoeal medicines are used to treat diarrhoea. These are called antimotility medicines and bulk-forming agents.

Antimotility medicines are used to treat acute diarrhoea. They include codeine phosphate, co-phenotrope, loperamide, and kaolin and morphine mixture. The most commonly used antimotility medicine is loperamide (ImodiumĀ®). Kaolin and morphine mixture is very rarely used to treat diarrhoea any more.

Bulk-forming agents are used for people who have diarrhoea because they have irritable bowel syndrome. They include ispaghula husk, methylcellulose and sterculia.

It is important to remember that antidiarrhoeal medicines are not the only treatments used for diarrhoea. Another important treatment is fluid replacement. See separate leaflets called Acute Diarrhoea in Children, and Acute Diarrhoea in Adults.

The rest of this leaflet deals only with antimotility medicines when they are used to ease the symptoms of acute diarrhoea. Bulk-forming agents are discussed in the separate leaflet called Irritable Bowel Syndrome.

How do antimotility medicines work?

Antimotility medicines work by slowing down the movement of your gut, which reduces the speed at which the contents pass through. Food remains in your gut for longer and this allows more water to be absorbed back into your body. This results in firmer stools that are passed less often.

Antimotility medicines reduce the number of times you need to go to the toilet, and can reduce the length of time you have diarrhoea for – but this is only in some people. Research studies have shown that loperamide may reduce the duration of diarrhoea by one day in some people.

Which antimotility medicines are normally used to treat acute diarrhoea?

Loperamide is the most commonly used antimotility medicine for acute diarrhoea. It is thought to be the safest and most effective antimotility medicine. Co-phenotrope and codeine are used much less often than loperamide.

As discussed above, kaolin and morphine mixture is an older treatment for acute diarrhoea and is very rarely used anymore.

When should I take an antimotility medicines?

For most adults and children older than 12 years, antimotility medicines are usually not necessary when they have a bout of diarrhoea. However, some people may wish to reduce the number of trips that they need to make to the toilet.

Children should not be given antimotility medicines. This is because some children have had very serious side-effects after they have taken these medicines.

How should I take antimotility medicines?

The following directions are for adults only:

Loperamide – the adult dose of this is two capsules at first. This is followed by one capsule after each time you pass some diarrhoea, up to a maximum of eight capsules in 24 hours.

Co-phenotrope – the adult dose is four tablets at first. Six hours later, take two more tablets. After that, take two tablets every six hours.

Codeine phosphate – for adults, the usual dose is one 15 mg tablet, up to four times a day.

What is the usual length of treatment?

Most people only need to take an antimotility medicine for a few days. In general, you should not take these medicines for longer than five days unless your doctor has told you to do so.

Can I buy antidiarrhoeal medicines?

You can buy loperamide and co-phenotrope from your local pharmacy. You can also get both of these medicines from your doctor, on prescription. Codeine phosphate is only available from your doctor, on a prescription.

You can only buy kaolin and morphine mixture from your local pharmacy, but quite a few pharmacies do not keep this medicine any more.

What are the possible side-effects?

The most commonly reported adverse effects of antimotility medicines are constipation and dizziness. They may also cause drowsiness. If this happens, do not drive or use tools or machines.

More rarely, they have been reported to cause abdominal cramps and bloating, skin rashes and itching.

Some children have very serious side-effects after they have taken these medicines – for example, necrotising enterocolitis (part of the gut dies), delirium, depressed breathing, and coma. Some children have died after taking these medicine – this is very rare.

For a full list of side-effects see the leaflet that comes with your medicine.

Who cannot take antidiarrhoeal medicines?

You should not take antimotility medicines if:

  • You are younger than 12 years of age.
  • You have blood or mucus in the stools, and a fever.
  • You have abdominal distention.
  • You have active ulcerative colitis (inflammation of the gut).
  • You have antibiotic-associated colitis (inflammation of the gut caused by antibiotics).

How to use the Yellow Card Scheme

If you think you have had a side-effect to one of your medicines, you can report this on the Yellow Card Scheme. You can report side-effects that:

  • Are not discussed in the leaflet that came with your medicine.
  • Cause problems that interfere with your everyday activities.
  • Happen if you take more than one medicine.

You can do this online at the following web address: http://yellowcard.mhra.gov.uk

The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that your medicines may have caused. If you wish to report a side-effect you will need to provide basic information about:

  • The side-effect.
  • The name of the medicine which you think caused it.
  • Information about the person who had the side-effect.
  • Your contact details as the reporter of the side-effect.

It is helpful if you have your medication and/or the leaflet that came with it with you while you fill out the report.

References and Disclaimer | Provide feedback


  • British National Formulary; 62nd Edition (Sep 2011) British Medical Association and Royal Pharmaceutical Society of Great Britain, London
  • Diarrhoea – adults assessment, Prodigy (December 2010)


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