Pharmacology of Fluid Motility

Question 1

causes of travellers diarrhoea

Answer 1

Enterotoxin producing E coli

also salmonela, shigella and campylobacteria

Question 2

the most common strain of bacteria causing gasstroenteritis in the UK is

Answer 2

Campylobacter jejuni

Question 3

non infectious causes of diarrhoea

Answer 3

IBS. IBD, bile salts excess and lactase deficiency
physiological factos eg anxiety
hyperthryoidism
drug induced - Mg salts, beta blockers, cytotoxic drugs

Question 4

goals in management of diarrhoea

Answer 4

maintain fluid and electrolyte balance
antimicrobial agents in sever infective causes
antimotility and spasmolytic agents - symptomatic

Question 5

rehydration in diarrhoea when fluid loss is severe

Answer 5

IV rehydration

Question 6

rehydration in diarrhoea normally

Answer 6

ORT - Restore & maintain hydration till diarrhoea ceases (spontaneously)

Question 7

which transporter does rehydration therapy exploit

Answer 7

SGLT1 - absorption of Na and glucose by SGLT1 cause accompanying absorption of water

Question 8

what type of relief do anti motility agents give

Answer 8

symptomatic

Question 9

what are anti motility agents contraindicated in

Answer 9

acute infective diarrhoea, IBS, IBD, diverticulosis

Question 10

examples of anti motility agents

Answer 10

opiates

• loperamide
• Diphenoxylate
• codeine

Question 11

what negative effect do opioid drugs have

Answer 11

constipating

Question 12

effects of opioid drugs

Answer 12

activate μ-receptors on myenteric neurones and cause hyperpolarization by increasing their potassium conductance.This inhibits acetylcholine release from the myenteric plexus and reduces bowel motility.

dec peristalsis, inc segmentation
inc fluid absorption
inc tone of large intestine

Question 13

benefits of loperamide

Answer 13

weak antimuscarinic effect
longer acting
best for local effect on gut as has little effect on the brain
therefore unlikely to cause dependence

Question 14

diphenoxylate

Answer 14

low CNS penetration
can contain atropine - discourage drug abuse due to side effects e.g. nausea, vomiting, blurred vision, headache, weakness

Question 15

and atropine is used in cardio for

Answer 15

bradycardia

Question 16

antidiarrhoeal agent examples

Answer 16

Racecadotril

Question 17

what is Racecadotril a pro drug of

Answer 17

thiorphan

Question 18

what is a pro drug

Answer 18

A prodrug is a medication or compound that, after administration, is metabolized into a pharmacologically active drug.

Question 19

how does one use Racecadotril

Answer 19

in children over 3 months of age as an adjunct to rehydration

Question 20

what are loperamide or diphenoxylate contraindicated in

Answer 20

children

Question 21

what does Racecadotril inhibit

Answer 21

enkephalinase inhibitor - inhibits the breakdown of endogenous opioids & reduces intestinal secretions.

Question 22

what can the Hirschprung disease cause

Answer 22

impairment of motility/defaecation reflex e.g. constipation

Question 23

compare laxative and purgative action

Answer 23

laxative produce a midler action resulting in passage of soft but formed stools
purgative produce a stronger action resulting in more fluid evacuation

Question 24

can the same drug act as laxatives and purgatives at different doses

Answer 24

yes - laxative at low, and purgative at high

Question 25

contraindications of laxatives and purgatives

Answer 25

physical obstruction in the bowel

Question 26

reasons of laxative dependency

Answer 26

- easily resorted to as OTC | - abused in eating disorders

Question 27

abuse of laxatives may result in what

Answer 27

hypokalaemia

Question 28

what does hypokalaemia do to you

Answer 28

make you tired or act as a stimulus for cardiac arrhythmias

Question 29

bulk laxative example

Answer 29

methycellulose

Question 30

bulk laxatives

Answer 30

inc volume of intestinal contents causing peristalsis | are indigestible polysaccharides

Question 31

osmotic laxatives mechanisms and examples

Answer 31

inc bulk in bowel by retaining water by an osmotic effect Mg sulphate or hydroxide sodium citrate lactulose

Question 32

Mg sulphate or hydroxide administration route | and lactulose

Answer 32

oral

Question 33

sodium citrate administration route

Answer 33

rectal

Question 34

stimulant purgatives examples

Answer 34

bisacodyl- orally or suppository senna sodium picosulfate

Question 35

name an anthraquinone laxative

Answer 35

senna

Question 36

faecal softeners examples

Answer 36

softeners - docusate sodium - oral lubricants - archis - oil as enema oral liquid paraffin

Question 37

which class of laxatives are abdominal cramps less common with

Answer 37

stimulant purgatives

Question 38

what is diarrhoea defined as

Answer 38

loss of fluid and solutes from the GI tract in excess of 500ml per day

Question 39

how does rotavrus cause diarrhoea

Answer 39

inhibition of Na/K/ATPase & structural damage to mucosal cells leading to reduced absorption

Question 40

stimulant laxative mechanism

Answer 40

inc motility by actin g on mucosa/nerve plexuses, which may be damaged due to prolonged drug use

Question 41

faecal softeners

Answer 41

promote defecation by softening or lubricating the stool