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Last updated on September 19, 2021

Community pharmacists may be asked by patients to treat existing diarrhea or to offer advice on what course of action to take should diarrhea occur, e.g. to holidaymakers. Diarrhoea is defined as an increased frequency of bowel evacuation, with the passage of abnormally soft or watery feces. The basis of treatment is electrolyte and fluid replacement; in addition, antidiarrhoeals are useful in adults and older children.

What you need to know

Age, Infant, child, adult, elderly, Duration, Severity, Symptoms, associated symptoms, Nausea/vomiting, Fever, Abdominal cramps, Flatulence, Other family members affected? Previous history, Recent travel abroad?, Causative factors, Medication, Medicines already tried, Other medicines being taken, Significance of questions and answers


Particular care is needed in the very young and the very old. Infants (younger than 1 year) and elderly patients are especially at risk of becoming dehydrated.


Most cases of diarrhoea will be acute and self-limiting. Because of the dangers of dehydration it would be wise to refer infants with diarrhea of longer than 1 day’s duration to the doctor.


The degree of severity of diarrhea is related to the nature and frequency of stools. Both these aspects are important, since misunderstandings can arise, especially in self-diagnosed complaints. Elderly patients who complain of diarrhoea may, in fact, be suffering from faecal impaction. They may pass liquid stools, but with only one or two bowel movements a day.


DiarrhoeaAcute diarrhoea is rapid in onset and produces watery stools that are passed frequently. Abdominal cramps, flatulence and weakness or malaise may also occur. Nausea and vomiting may be associated with diarrhea, as may fever. The pharmacist should always ask about vomiting and fever in infants; both will increase the likelihood that severe dehydration will develop. Another important question to ask about diarrhoea in infants is whether the baby has been taking milk feeds and other drinks as normal. Reduced fluid intake predisposes to dehydration.

The pharmacist should question the patient about food intake and also about whether other family members or friends are suffering from the same symptoms, since acute diarrhea is often infective in origin. Often there are localised minor outbreaks of gastroenteritis, and the pharmacist may be asked several times for advice and treatment by different patients during a short period of time. Types of infective diarrhoea are discussed later in this post.

The presence of blood or mucus in the stools is an indication for referral. Diarrhoea with severe vomiting or with a high fever would also require medical advice.

Previous history

A previous history of diarrhea or a prolonged change in bowel habit would warrant referral for further investigation and it is important that the pharmacist distinguish between acute and chronic conditions. Chronic diarrhoea (of more than 3 weeks’ duration) may be caused by bowel conditions such as Crohn’s disease, irritable bowel syndrome (Irritable bowel syndrome) or ulcerative colitis and requires medical advice.

Recent travel abroad

Diarrhea in a patient who has recently travelled abroad requires referral since it might be infective in origin. Gardiasis should be considered in travellers recently returned from South America or the Far East.

Causes of diarrhea


Most cases of diarrhoea are short lived, the bowel habit being normal before and after. In these situations the cause is likely to be infective (viral or bacterial).

Viral. Viruses are often responsible for gastroenteritis. In infants the virus causing such problems often gains entry into the body via the respiratory tract (rotavirus). Associated symptoms are those of a cold and perhaps a cough. The infection starts abruptly and vomiting often precedes diarrhea. The acute phase is usually over within 2-3 days, although diarrhoea may persist. Sometimes diarrhea returns when milk feeds are reintroduced. This is because one of the milk-digestive enzymes is temporarily inactivated. Milk therefore passes through the bowel undigested, causing diarrhoea. The health visitor or doctor would need to give further advice in such situations.

Whilst in the majority the infection is usually not too severe and is self-limiting, it should be remembered that rotavirus infection can cause death. This is most likely in those infants already malnourished and living in poor social circumstances who have not been breastfed.

Bacterial. These are the food-borne infections previously known as food poisoning. There are several different types of bacteria that can cause such infections: Staphylococcus, Campylobacter, Salmonella, Shigella, pathogenic Escherichia coli, Bacillus cereus and Listeria monocytogenes. The typical symptoms include severe diarrhea and/or vomiting, with or without abdominal pain. Two commonly seen infections are Campylobacter and Salmonella, which are often associated with contaminated poultry, although other meats have been implicated. Contaminated eggs have also been found to be a source of Salmonella. Kitchen hygiene and thorough cooking are of great importance in preventing infection.

Features of some infections causing diarrhoea.


Infection Incubation Duration Symptoms
Staphylococcus 2-6 h 6-24 h Severe, short lived; especially vomiting
Salmonella 12-24 h 1-7 days Mainly diarrhoea
Campylobacter 2-7 days 2-7 days Diarrhea with abdominal colic
B. cereus 1-5 h 6-24 h Vomiting
B. cereus (two types of infection) 8-16 h 12-24 h Diarrhoea
L. monocytogenes 3-70 days   Flulike, diarrhoea

Table summarises the typical features of some of the following infections:

  • Bacillary dysentery is caused by Shigella. It can occur in outbreaks where there are people living in close proximity and may occur in travellers to Africa or Asia.
  • B. cereus is usually associated with cooked rice, especially if it has been kept warm or has been reheated. It presents with two different clinical pictures, as shown in Table.
  • E. coli infections are less common but can be severe with toxins being released into the body, which can cause kidney failure.
  • L. monocytogenes can cause gastroenteritis or a flulike illness. On occasion it can be more severe and cause septicaemia or meningitis. Pregnant woman are more susceptible to it but it is still a rare infection occurring in 1 in 20,000 pregnancies. Infection during pregnancy can cause miscarriage, still birth or an infection of the newborn. Foods to be avoided during pregnancy include unpasteurised cheese, soft ripe cheeses, blue-veined cheeses, pates, cold cuts of meat and smoked fish. Pregnant women with diarrhoea or fever should be referred to their midwife or general practitioner.

Antibiotics are generally unnecessary as most food-borne infections resolve spontaneously. The most important treatment is adequate fluid replacement. Antibiotics are used for Shigella infections and the more severe Salmonella or Campylobacter ones. Ciprofloxacin may be used in such circumstances.

  • Protozoan infections are uncommon in Western Europe but may occur in travellers from further afield. Examples include Entamoeba histolytica (amoebic dysentery) and Giardia lamblia (giardiasis). Diagnosis is made by sending stool samples to the laboratory.

Chronic diarrhoea

Recurrent or persistent diarrhea may be due to an irritable bowel or, more seriously, a bowel tumour, an inflammation of the bowel (e.g. ulcerative colitis or Crohn’s disease), an inability to digest or absorb food (malabsorption, e.g. coeliac disease) or diverticular disease of the colon.

Irritable bowel syndrome

This non-serious, but troublesome, condition is one of the more common causes of recurrent bowel dysfunction in adolescents and young adults. The patient usually describes the frequent passage of small volumes of stool rather than true diarrhea. The stools are typically variable in nature, often loose and semiformed. They may be described as being like rabbit droppings or pencil shaped. The frequency of bowel action is also variable as the diarrhoea may alternate with constipation. Often the bowels are open several times in the morning before the patient leaves for work.

The condition is more likely to occur at times of stress, it may be associated with anxiety and, occasionally, it may be triggered by a bowel infection. Inadequate dietary fibre may also be of significance. It is possible that certain foods can irritate the bowel, but this is difficult to prove. There is no blood present within the motion in an irritable bowel. Bloody diarrhea may be a result of an inflammation or tumour of the bowel. The latter is more likely with increasing age (from middle age onwards) and is likely to be associated with a prolonged change in bowel habit; in this case diarrhoea might sometimes alternate with constipation.


Medicines already tried

The pharmacist should establish the identity of any medication that has already been taken to treat the symptoms in order to assess its appropriateness.

Other medicines being taken

Details of any other medication being taken (both over the counter and prescribed) are also needed, as the diarrhea may be drug induced (Table Some drugs that may cause diarrhea). over the counter medicines should be considered; commonly used medicines such as magnesium-containing antacids and iron preparations are examples of medicines that may induce diarrhoea. Laxative abuse should be considered as a possible cause.

Some drugs that may cause diarrhea.

Antacids: Magnesium salts
Antihypertensives: methyldopa; beta-blockers (rare)
Digoxin (toxic levels)
Diuretics (furosemide)
Iron preparations
Non-steroidal anti-inflammatory drugs
Selective serotonin reuptake inhibitors

When to refer

Diarrhea of greater than

1 day’s duration in children younger than 1 year

2 days’ duration in children under 3 years and elderly patients

3 days’ duration in older children and adults

Association with severe vomiting and fever

Recent travel abroad

Suspected drug-induced reaction to prescribed medicine

History of change in bowel habit

Presence of blood or mucus in the stools


Treatment timescale

One day in children; otherwise 2 days.


Oral rehydration therapy

The risk of dehydration from diarrhea is greatest in babies, and rehydration therapy is considered to be the standard treatment for acute diarrhoea in babies and young children. Oral rehydration sachets may be used with antidiarrhoeals in older children and adults.

Rehydration may still be initiated even if referral to the doctor is advised. Sachets of powder for reconstitution are available; these contain sodium as chloride and bicarbonate, glucose and potassium. The absorption of sodium is facilitated in the presence of glucose. A variety of flavours are available.

It is essential that appropriate advice be given by the pharmacist about how the powder should be reconstituted. Patients should be reminded that only water should be used to make the solution (never fruit or fizzy drinks) and that boiled and cooled water should be used for children younger than 1 year. Boiling water should not be used, as it would cause the liberation of carbon dioxide. The solution can be kept for 24 h if stored in a refrigerator. Fizzy, sugary drinks should never be used to make rehydration fluids, as they will produce a hyperosmolar solution that may exacerbate the problem. The sodium content of such drinks, as well as the glucose content, may be high.

Home-made salt and sugar solutions should not be recommended, since the accuracy of electrolyte content cannot be guaranteed, and this accuracy is essential, especially in infants, young children and elderly patients. Special measuring spoons are available; their correct use would produce a more acceptable solution, but their use should be reserved for the treatment of adults, where electrolyte concentration is less crucial.


Parents sometimes ask how much rehydration fluid should be given to children. The following simple rules can be used for guidance; the amount of solution offered to the patient is based on the number of watery stools that are passed. Table provides the volumes required per watery stool.

Amount of rehydration solution to be offered to patients

Age Quantity of solution (per watery stool)
Under 1 year 50 mL (quarter of a glass)
1-5 years 100 mL (half a glass)
6-12 years 200 mL (one glass)
Adult 400 mL (two glasses)

Other therapy


Loperamide is an effective antidiarrhoeal treatment for use in older children and adults. When recommending loperamide the pharmacist should remind patients to drink plenty of extra fluids. Oral rehydration sachets may be recommended. Loperamide may not be recommended for use in children under 12 years.

Diphenoxylate/atropine (Co-phenotrope)

Co-phenotrope can be used as an adjunct to rehydration to treat diarrhea in those aged 16 years and over.


Kaolin has been used as a traditional remedy for diarrhoea for many years. Its use was justified on the theoretical grounds that it would absorb water in the Gastrointestinal tract and would absorb toxins and bacteria onto its surface, thus removing them from the gut. The latter has not been shown to be true and the usefulness of the former is questionable. The use of kaolin-based preparations has largely been superseded by oral rehydration therapy, although patients continue to ask for various products containing kaolin.


Morphine, in various forms, has been included in antidiarrhoeal remedies for many years. The theoretical basis for its inclusion is that morphine, together with other narcotic drugs such as codeine, is known to slow the action of the Gastrointestinal tract; indeed, constipation is a well-recognised side-effect of such drugs. However, at the doses included in most over the counter preparations, it is unlikely that such an effect would be produced. Kaolin and morphine mixture remains a popular choice for some patients, despite the lack of evidence of its effectiveness.

Practical points

  1. Patients with diarrhoea should be advised to drink plenty of clear, non-milky fluids, such as water and diluted squash.
  2. NHS Clinical Knowledge Service (CKS) says that the patient can be advised to continue their usual diet but that fatty foods and foods with a high sugar content might be best avoided as they may not be well tolerated.
  3. Breast- or bottle feeding should be continued in infants. The severity and duration of diarrhea are not affected by whether milk feeds are continued. A well-nourished child should be the aim, particularly where the infant is poorly nourished to begin with and where the withholding of milk feeds may be more detrimental than in a well-nourished infant, where temporary withdrawal is unimportant. Some doctors continue nevertheless to advise the discontinuation of milk, especially bottle, during the acute phase of infection.

Diarrhea in practice

Case 1

Mrs Robinson asks what you can recommend for diarrhea. Her son David, aged 11 years, has diarrhoea and she is worried that her other two children, Natalie, aged 4 years, and Tom, aged just over 1 year, may also get it. David’s diarrhoea started yesterday; he went to the toilet about five times and was sick once, but has not been sick since. He has griping pains, but is generally well and quite lively. Yesterday he had pie and chips from the local takeaway during his lunch break at school. No one else in the family ate the same food. Mrs Robinson has not given him any medicine, but has some kaolin and morphine mixture at home and wants to know if David could take some, and also if the other children could take it if necessary.

The pharmacist’s view

It sounds as if David has a bout of acute diarrhea, possibly caused by the food he ate yesterday during lunchtime. He has vomited once, but now the diarrhoea is the problem. The child is otherwise well. He is 11 years old, so the best plan would be to start oral rehydration with some proprietary sachets, with advice to his mother about how they should be reconstituted. Kaolin and morphine mixture should not be given to children under 12, and in any case it is not considered first-line treatment for diarrhoea. If either or both the other children get diarrhea, they can also be given some rehydration solution. David should see the doctor the day after tomorrow if his condition has not improved.

The doctor’s view

David’s diarrhoea could well be due to food poisoning. Oral rehydration is the correct treatment. He should also be told not to eat anything for the next 24 h or so until the diarrhea has settled. If he wants to drink other fluids in addition to the electrolyte mixture, he should be told to avoid milk.

His symptoms should settle down over the next few hours. If they persist or he complains of worsening abdominal pain, particularly in the lower right side of the abdomen, his mother should contact the doctor. An atypical acute appendicitis may present with symptoms of a bowel infection.

Case 2

Mrs Choudry is collecting her regular repeat prescription for antihypertensive treatment. You ask how she and the family are, and she tells you that several members of the family have been suffering with diarrhea on and off. You know that the family recently returned from a trip to India where they had been visiting relatives to attend a family wedding. In answer to your questions, Mrs Choudry tells you that the problem with the diarrhoea started after they returned.

The pharmacist’s view

Referral to the general practitioner is needed here as the diarrhea may be related to the recent travel.

The doctor’s view

Referral is a sensible course of action. Clearly, more information is required, e.g. date of onset of symptoms and date of return to the UK. It does not sound as if any of the family are acutely ill but it would be necessary to ensure that no one is dehydrated. If the diarrhea is persisting, it would be helpful to send stool samples to the local public health laboratory for analysis. It is possible that they may be suffering from giardiasis, which can be treated with metronidazole. Sometimes stool samples come back showing no signs of infection, in which case the diarrhoea is considered as being due to postinfection irritability of the bowel. This usually resolves spontaneously with no specific treatment.

Case 3

Mrs Jean Berry wants to stock up on some medicines before her family sets off on their first holiday abroad; they will be going to Spain next week. Mrs Berry tells you that she has heard of people whose holidays have been ruined by holiday diarrhoea and she wants you to recommend a good treatment. On questioning, you find out that Mr and Mrs Berry and their two boys aged 10 and 14 years will be going on the holiday.

The pharmacist’s view

Holiday diarrhea can often easily be dealt with. Mrs Berry could be advised to buy some loperamide capsules, which would be suitable treatment for her, Mr Berry and their 14-year-old son. In addition, she should purchase some oral rehydration sachets for the younger son. The sachets could also be used by other family members.

The pharmacist could also give some valuable advice about the avoidance of potential problems by the Berry family on their first foreign holiday. Fresh fruit should be peeled before eating and hot food should not be eaten other than in restaurants. Roadside snack stalls are best avoided. The question of the quality of drinking water often crops up. Good advice to travellers would be to check with the tour company representative as to the advisability of drinking local water. If in doubt, bottled mineral water can be drunk; such water (the still variety) could also be used to reconstitute rehydration sachets. Ice in drinks may be best avoided, depending on the water supply.

Holiday diarrhoea is usually self-limiting, but if it is still present after several days, medical advice should be sought. If the diarrhea persists or is recurrent after returning home, the doctor should be seen. Finally, patients would be well advised to be wary of buying over the counter medicines abroad. In some countries, a large range of drugs including oral steroids and antibiotics can be purchased over the counter. Each year, patients return to Britain with serious adverse effects following the use of oral chloramphenicol, for example, which has been prescribed or purchased.

The doctor’s view

The pharmacist has covered all the important points. The most likely cause of diarrhoea would be contaminated food or water. The best treatment of acute diarrhea is to stop eating and to drink bottled mineral water (with or without electrolyte reconstitution powders). It would be sensible to take an antidiarrhoeal such as loperamide.

Case 4

Mr Radcliffe is an elderly man who lives alone. Today, his home help asks what you can recommend for diarrhoea, from which Mr Radcliffe has been suffering for 3 days. He has been passing watery stools quite frequently and feels rather tired and weak. He has sent the home help because he dare not leave the house and go out of reach of the toilet. You check your PMRs (patient medication records), which confirm your memory that he takes several different medicines: digoxin, furosemide and paracetamol. Last week you dispensed a prescription for a course of amoxicillin. The home help tells you that he has been eating his usual diet and there does not seem to be a link between food and his symptoms.

The pharmacist’s view

Mr Radcliffe’s diarrhoea may be due to the amoxicillin, which he started to take a few days ago. It would be best to call the patient’s doctor to discuss the appropriate course of action because Mr Radcliffe’s other drug therapy means that fluid loss and dehydration may cause electrolyte imbalance and put him at further risk. The doctor may decide to stop the amoxicillin.

The doctor’s view

It is likely that the amoxicillin has caused the diarrhea. The most important consideration in management is to ensure adequate fluid and electrolyte replacement. This is particularly so as the elderly (and babies) are not as resilient to the effects of dehydration. In Mr Radcliffe’s case things are further complicated by his other medication: furosemide and digoxin. He is not on any potassium supplement or a potassium-sparing diuretic. Although there may be good reason for this, diuretics such as furosemide can lower the plasma potassium level and make digoxin dangerously toxic. Unfortunately, potassium can also be lost in diarrhoea, further aggravating this problem. It is therefore reasonable to ask for the doctor to visit and assess.

There is also a possibility that the diarrhea could be due to a bacterium (Clostridium difficile) in the colon. It is thought that antibiotics (Mr Radcliffe was given amoxicillin) upset the normal bowel flora allowing C. difficile to flourish. This condition can be caused by most antibiotics, but has been reported most often with clindamycin, ampicillin, amoxicillin and the cephalosporins. The condition is more likely to occur in those over the age of 65 years. It is now most commonly seen in hospitals where it is thought that the infection is spread by health workers.

The diarrhoea of a C. difficile infection can range from mild self-limiting symptoms to severe protracted or recurrent episodes and can sometimes be fatal. There is often a low-grade fever, and abdominal pain/cramps may occur. The symptoms usually begin within 1 week of starting antibiotic treatment but may start up to 6 weeks after a course of antibiotics. It is sometimes necessary to treat severe cases with metronidazole or vancomycin.

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