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Acute diarrhoea is defined as diarrhoea which starts suddenly and lasts for less than two weeks. Often no medicines are needed. Antidiarrhoeal medicines reduce the number of times that you need to go to the toilet, when you have acute diarrhoea. The most commonly used medicine is loperamide. You can buy this from your local pharmacy or get it on prescription from your doctor. Most people only need to take these medicines for a few days. Children under the age of 12 years should not take antidiarrhoeal medicines unless their doctor has told them to do so.

Diarrhoea is the passing of frequent loose or liquid stools (faeces). When this change to the stools starts suddenly and lasts for less than two weeks, the condition is known as acute diarrhoea. If it lasts more than two weeks, it is called persistent diarrhoea. If it lasts more than four weeks it is called chronic diarrhoea. 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 side-effects from some medicines, food allergy and anxiety.
  • Gut disorders that cause chronic diarrhoea may be mistaken for acute diarrhoea when they first begin - for example, diarrhoea caused by ulcerative colitis.

Usually no treatment is required when you have acute diarrhoea, other than drinking plenty of fluids.

See the separate leaflets called Diarrhoea and Acute Diarrhoea in Children.

Antidiarrhoeal medicines are used to reduce the number of trips that you need to make to the toilet when you have diarrhoea. Two main 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 (Imodium®). Kaolin and morphine mixture is very rarely used to treat diarrhoea nowadays. Antimotility medicines are not advised for children under the age of 12.
  • Bulk-forming agents are used for people who have diarrhoea because they have irritable bowel syndrome. They include ispaghula husk, methylcellulose and sterculia.

Antisecretory medicines are another group of treatments not used very much in the UK. They are designed to be used with rehydration treatment. They reduce the amount of water that is released into the gut during an episode of diarrhoea. They can be used for children who are older than 3 months of age and for adults. The only one licensed in the UK is racecadotril (Hidrasec®). This is not recommended for use in Scotland, because it is not clear how effective it is. National Institute for Health and Care Excellence (NICE) guidelines do not encourage its use either in the UK.

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

The rest of this leaflet deals only with antimotility medicines when they are used to ease the symptoms of acute diarrhoea. For information on bulk-forming agents, see separate leaflet called Irritable Bowel Syndrome.

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. This can be helpful in allowing you to continue your normal activities, or if you need to travel anywhere. However, there is no convincing evidence that they reduce the duration of the diarrhoea. Most cases of acute diarrhoea get better on their own in exactly the same amount of time, whether you take any medicines or not.

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 nowadays.

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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. For example, if you have to make an essential journey, taking antimotility medicines may help to make this possible.

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

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.

You can buy loperamide and co-phenotrope from your local pharmacy. You can also obtain 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.

Antisecretory medicines are only available from your doctor, on prescription.

The most commonly reported adverse effects of antimotility medicines are constipation and dizziness. They can make you feel sick (nauseated), cause a headache, or give you wind. They may also cause drowsiness. If this happens, do not drive and do not use tools or machines.

More rarely, they have been reported to cause tummy (abdominal) cramps, a dry mouth, skin rashes and itching.

Some children have very serious side-effects after they have taken these medicines - for example:

  • A condition where part of the gut dies (necrotising enterocolitis).
  • Confusion.
  • Depressed breathing.
  • Coma.

Some children have died after taking these medicines - this is very rare. However, this is why these medicines are not recommended for children.

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

You should not take antimotility medicines if:

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 do this online at

The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that medicines or any other healthcare products 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.
  • 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.

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Further reading and references