2: Physiology and pharmacology of fluid balance and motility

Question 1

Diarrhoea is defined as the loss of at least ___mls of fluid per day from the GI tract.

Answer 1

500

Question 2

Which ion does water follow into GI cells?

Answer 2

Na⁺

Question 3

Water moves into GI tract cells by ___.

Answer 3

osmosis

Question 4

Which transporter couples the influx of glucose and Na⁺ into enterocytes?

Answer 4

SGLT1

Question 5

Apart from glucose, which other molecule is sodium ion influx coupled to?

Answer 5

Amino acid influx

Question 6

Which types of GI tract infection can cause diarrhoea?

Answer 6

Viral

Bacterial

Parasitic

Question 7

What is the most common bacterium causing diarrhoea in the UK?

Answer 7

Campylobacter jejuni

Question 8

Which bacterium most commonly causes Traveller’s diarrhoea?

Answer 8

EnteroTOXIC E. coli

Question 9

What non-infectious GI diseases can cause diarrhoea?

Answer 9

IBD

IBS

Lactase deficiency

Question 10

Why does hyperthyroidism cause diarrhoea?

Answer 10

Increased motility

Question 11

What infection can the use of broad spectrum antibiotics cause?

Answer 11

Clostridium difficile

leads to colitis, diarrhoea

Question 12

Increased levels of which molecules lead to increased expression of channels causing increased secretion into the gut?

Answer 12

cAMP

Question 13

Toxins produced by infectious agents stimulate the enzyme ___ ___, which increase the levels of ____, which increases gut secretion causing diarrhoea.

Answer 13

adenylyl cyclase , cAMP/?cGMP

Question 14

Diarrhoea can lead to ___ due to water loss.

Answer 14

dehydration

Question 15

Diarrhoea can lead to ___ ___ due to bicarbonate loss.

Answer 15

metabolic acidosis

Question 16

Diarrhoea can lead to ___ due to potassium loss.

Answer 16

hypokalaemia

Question 17

Which disease, causing profuse watery diarrhoea, can be fatal if severe?

Answer 17

Cholera

Question 18

What is the first line therapy for severe diarrhoea?

Answer 18

Fluid replacement (oral/IV)

Question 19

Is coupled glucose/Na absorption affected by diarrhoea?

Answer 19

No - this is why fluid replacement therapy works

Question 20

Which channel is used in rehydration therapy?

Answer 20

SGLT1

Question 21

Why is salt solution used in rehydration therapy?

Answer 21

Takes advantage of coupled glucose/Na transport through SGLT1

And then water follows Na, causing rehydration

Question 22

What do oral rehydration fluids contain?

Answer 22

Glucose

Sodium

to take advantage of SGLT1 ⇒ rehydration

Question 23

Why are antibiotics used in a limited role in managing diarrhoea?

Answer 23

Most infections are VIRAL (rotavirus, norovirus)

Most bacterial infections are self-limiting so what’s the point in using antibiotics

Question 24

Antibiotics are useful in (self-limiting / severe) diarrhoea.

Answer 24

severe

Question 25

Anti-motility agents (loperamide, opiates) are only used in (mild / severe) cases of diarrhoea.

Answer 25

mild

you want the mucosa and toxins to be flushed out of the system - anti-motility agents slow this down

Question 26

Opioids cause ___ by decreasing the rate of peristalsis and constricting sphincters.

Answer 26

constipation

Question 27

Does the body develop a tolerance to the constipating effects of opioids?

Answer 27

No

Question 28

What are some anti-motility agents used in diarrhoea?

Answer 28

Loperamide (imodium)

Diphenoxylate

Codeine

Question 29

Why is atropine added to the antimotility agent diphenoxylate?

Answer 29

Discourages abuse of diphenoxylate through side effects (nausea, headache, weakness, blurred vision)

Question 30

What is constipation?

Answer 30

Production of hard stools requiring straining to pass

and/or

sense of incomplete defecation

Question 31

What is the higher strength version of a laxative?

Answer 31

Purgative

Question 32

Many drugs act as laxatives in ___ doses and purgatives in ___ doses.

(low / high)

Answer 32

low , high

Question 33

Which drugs should not be used when there is physical obstruction in the bowel?

Answer 33

Laxatives

Purgatives

Question 34

Patients with ___ ___ may abuse laxatives to lose weight.

Answer 34

eating disorders

Question 35

Why are patients with hernia, angina, eye surgery indicated for laxatives?

Answer 35

Straining increases intra-abdominal pressure which will exacerbate the condition

Question 36

Why would laxatives be given to haemorrhoid patients?

Answer 36

Rectal bleeding risk

Question 37

The use of which class of drug causes constipation and indicates the use of laxatives?

Answer 37

Opioids