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Pharmacology > Anti-Diarrhoeals > Flashcards

Anti-Diarrhoeals Flashcards

1
Q

What is diarrhoea?

A

Passage of unformed stools more frequently than normal for an individual
Roughly >3 times per day
Often accompanied by faecal urgency, nausea, vomiting and abdominal pain

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2
Q

What are the three types of diarrhoea?

A

Acute <14 days
Persistent 14-28 days
Chronic >28 days

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3
Q

What does diarrhoea result in?

A

Increased motility
Reduced absorption
Increased secretion of fluids/ electrolytes

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4
Q

What are the causes of diarrhoea?

A

Existing chronic disease
Infectious agents
Drugs
Psychological factors

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5
Q

What are some chronic diseases that can cause diarrhoea?

A

IBD
Gut resections
Motor abnormalities of IBS
Celiac disease
Mal absorption
Endocrine disorders
(All lead to loss of functioning mucosa)

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6
Q

What are some of the infectious agents that can cause diarrhoea?

A

Viral gastroenteritis
Bacterial pathogens
Parasites / protozoa

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7
Q

How do the rotavirus and norovirus cause diarrhoea?

A

Damaging the small bowel villi
Causes a net secretion of substances
Mild watery stools

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8
Q

Describe how adhesive enterotoxigenic bacteria cause diarrhoea

A

E.G. V cholerae, E. coli
Adhere to brush borders of intestinal absorptive cells
Secrete enterotoxins
Alter fluid electrolyte transport
Increases PG activity
Increases enteric NS activity
Severe watery stools

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9
Q

Explain how invasive bacteria cause diarrhoea

A

E.G. C. difficile, salmonella
Invade endothelium
Secrete enterotoxins
Cause inflammation
Tissue destruction
Bloody and watery stools

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10
Q

What drugs can cause diarrhoea?

A

Propanolol
Parasympathomimetics
Levodopa
Indomethacin
Digoxin
Antacids
Metformin
Laxatives

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11
Q

Is there a relationship between antibiotic use and diarrhoea?

A

Antibiotics may cause diarrhoea in 5-35% of individuals
Depends on the antibiotic, pathogen and underlying host health
Antibiotics disrupt normal microbiota leading to metabolic imbalances.

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12
Q

What impact can severe diarrhoea have?

A

It interferes with the absorption of drugs such as the contraceptive pill, anti convulsants and warfarin

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13
Q

What should be the first concern when dealing with (severe) diarrhoea?

A

Rehydration therapy
Priority over reducing stool fluid output
Oral hydration first
If electrolyte imbalances are severe move to IV fluid
Food intake should be maintained

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14
Q

What does rehydration therapy do?

A

Corrects electrolyte imbalance, fluid imbalance and acidosis
Increases water absorption and electrolytes
Alkalinising agent included to counter acidosis
Hypo osmolar solutions to avoid osmotic diarrhoea

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15
Q

What are the components of the WHO oral rehydration therapy?

A

Sodium
Potassium
Chlorine
Citrate (Alkali)
Glucose

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16
Q

What do anti-motility agents do?

A

Stop the movement of substances along the intestine
Less frequent bowel movements
Not good for infectious diarrhoea
Relieves symptoms of acute uncomplicated diarrhoea in adults

17
Q

When are anti-motility agents used?

A

Can be used in immediate cases to pause diarrhoea but won’t ‘stop’ it
Should not be used in children

18
Q

List some examples of opiate like anti diarrhoeals

A

Diphenoxylate
Codeine
Loperamide (Imodium)

19
Q

How do opiate like anti diarrhoeals work?

A

They act on mu opioid and serotonin receptors in the myenteric plexus
Decreases ACh release
Decreased peristaltic activity
Increased segmental activity / tone
Increased transit time
Increased time for fluid absorption

20
Q

What are the side effects of opiate like anti diarrhoeals?

A

Constipation
Abdominal cramps
Bloating

21
Q

What are the side effects of codeine and diphenoxylate?

A

Cross the blood brain barrier causing
Euphoria
Respiratory depression
Drowsiness
Tolerance and dependence
Restrict to severe cases only

22
Q

What is cophenotrope?

A

A combination of diphenoxylate and atropine
Typical anti muscarinic side effects
Dry mouth, blurred vision

23
Q

What can happen due to chronic use of opiate like agents?

A

Paralytic ileus and toxic mega colon
Paralyses peristaltic movement, bacteria can proliferate, colon can become distended

24
Q

What are some other anti diarrhoeal agents?

A

Stool modifiers
Antibiotics
Vaccines

25
Q

What are stool modifiers?

A

Absorbent clays
Recommended for chronic cases

26
Q

What do stool modifiers do?

A

Bulking action
Increase stool consistency
Potentially absorb micro organisms or toxins
Could provide a protective coating to the mucosa to prevent bacteria and toxins adhering

27
Q

What does bismuth salicylate do?

A

Pepto bismol
Promotes intestinal sodium and water reabsorption
Attenuates intestinal secretion
Binds to enterotoxins
Has direct anti bacterial effect
Prophylactic use in some countries
Discolours the tongue and teeth

28
Q

What antibiotics are used to treat diarrhoea?

A

Rifaximin - benefit in combination with anti motility agent
Ciproflaxacin - campilobacter jejuni
Tetracyclin - severe cholera

29
Q

When should vaccines be used to treat diarrhoea?

A

For typhoid and and cholera infections
Especially in developing countries where sanitation is poor

30
Q

What is the dukoral oral vaccine?

A

A mixture of inactivated vibrio cholerae bacteria and non toxic component of the toxic bacteria being treated

31
Q

What is the protective efficacy of the dukoral oral vaccine?

A

V cholera - 85%
Enterotoxigenic E. coli - 67%
Travellers diarrhoea - 43%

32
Q

Name some of the novel anti disrrhoeal approaches

A

Racecadortil
Novel anti secretory angents
Probiotics
Zinc supplements

33
Q

What does racecadotril do?

A

Destroys the bodies natural opioid peptides
Enkephalinase inhibitor - prevents metabolism of opioid peptides secreted by myenteric and submucosal plexus
Augments opioid effects on decreased fluid secretion, propulsive motility
Safe for acute diarrhoea in children

34
Q

What are novel antisecretory agents?

A

Chloride channel blockers
Prostaglandin analogs

35
Q

How do probiotics help?

A

Optimise mucosal immune responses to infections
Possible applications of acute childhood diarrhoea, antibiotic associated diarrhoea, prophylaxis of traveller diarrhoea and IBD

36
Q

How do zinc supplements help?

A

Decreased duration and severity of of diarrhoea
Decreased mortality (especially children younger than five)
Unsure of mechanism

Pharmacology (18 decks)

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