GI Pharmacology - Resit

Question 1

H2 histamine receptor antagonist mechanism

Answer 1

• competitive antagonists of H2 receptors, which are activated by histamine
• when activated, it increased activity of the proton pump by increased cAMP via PKA
• by blocking this, there is reduced acid production
• reduce secretion evoked by gastrin and ACh

Question 2

NSAIDs mechanism

Answer 2

• COX is formed from arachidonic acid

- reduce prostaglandin formation, via COX 1 inhibition

Question 3

PPIs mechanism

Answer 3

• inhibit membrane inserted H+/K+ dependent ATPase

- pumps in the tubulovesicles are not inhibited

Question 4

NSAIDs side effects

Answer 4

• gastric ulceration

- bleeding

Question 5

what drug can be used to prevent gastric damage, due to long term NSAID use? what does it do?

Answer 5

PGE1 analogue (e.g misoprostol)

• inhibits basal and food stimulated gastric acid formation
• maintains/increases secretion of mucus and bicarbonate

Question 6

what 3 things promote peptic ulcer healing?

Answer 6

• reduced acid secretion
• increased mucosal resistance
• eradicating H.pylori

Question 7

why must PPIs make it to the canaliculus of the stomach?

Answer 7

so they can be activated here, due to the acidic pH (they are prodrugs)

Question 8

why must PPIs make it to the canaliculus of the stomach?

Answer 8

so they can be activated here, due to the acidic pH

Question 9

example of a PPI?

Answer 9

omeprazole

Question 10

what gastric acid production are H2 histamine receptor antagonist effective against?

Answer 10

basal and stimulated

Question 11

examples of H2 histamine receptor antagonist

Answer 11

ranitidine and cimetidine

Question 12

sucralfate (mucosal strengtheners) mechanism

Answer 12

• activated in an acidic environment
• releases aluminium to acquire a strong negative charge
• blinds to ulcer base, forming a complex gel with mucus
• barrier against acid and pepsin

Question 13

what does sucralfate do?

Answer 13

increases

• mucosal blood flow
• mucus
• bicarbonate
• prostaglandin

Question 14

bismuth chealate (mucosal strengthener) is used for?

Answer 14

• H.pylori, as it promotes eradication

Question 15

what are laxatives?

Answer 15

agents that are used to treat constipation

Question 16

what are purgatives?

Answer 16

agents that cause purging (cleansing) of the bowels, by promoting evacuation

Question 17

when should laxatives/purgatives NOT be used?

Answer 17

when there is a physical obstruction to the bowel

Question 18

3 uses of laxatives/purgatives?

Answer 18

1. when straining is damaging to health or defecation is painful
2. clearing the bowel before a procedure
3. to treat drug induced constipation or constipated bedridden/elderly patients

Question 19

what are bulk laxatives? examples?

Answer 19

indigestible polysaccharide polymers e.g methylcellulose, ispagula husk

Question 20

what is slow and fast acting, out of bulk and osmotic laxatives?

Answer 20

bulk is slow, osmotic is fast

Question 21

what are osmotic laxatives? examples?

Answer 21

poorly absorbed solutes

e.g magnesium sulphate/hydroxide, sodium citrate (rectally), lactulose

Question 22

what do bulk and osmotic laxatives do to the body?

Answer 22

retain H20, increase bulk, increase peristalsis

Question 23

what are stimulant purgatives? examples?

Answer 23

increase water and electrolyte secretion from colonic mucosa and increase peristalsis

e.g senna, bisocodyl,

Question 24

examples of faecal softners?

Answer 24

docusate sodium (orally) 
arachis oil (enema)

Question 25

what drug is used for acute attacks in IBD?

Answer 25

glucocorticoids (e.g prednisolone, budesonide)

Question 26

what drugs are used in UC? examples?

Answer 26

aminosalicylates e.g sulfasalazine, mesalazine, olsalazine, balsalazide

Question 27

what do aminosalicylates all have present?

Answer 27

5-ASA (aminosalicylic acid)

Question 28

what transporter does rehydration therapy exploit?

Answer 28

SGLT1

Question 29

what is the mechanism of rehydration therapy?

Answer 29

- 2 Na+ bind, so affinity for glucose increases and it binds - Na+ and glucose move from out of the cell to inside, via SGLT1 - Na+ dissociate and affinity for glucose falls, it dissociates - this causes accompanying absorption oh H20

Question 30

what type of drugs are used as anti motility/diarrhoeal drugs?

Answer 30

opiates (morphine like)

Question 31

5 actions of opiates on the ailmentary tract?

Answer 31

- inhibition of enteric neurones - decreases peristalsis, increased segmentation - increased fluid absoroption - constriction of pylorid, ileocaecal and anal sphincters - increased tone of LI

Question 32

what can be used to dissolve non calcified cholesterol gallstones?

Answer 32

Ursodeoxycholic acid

Question 33

two treatments for biliary spasm?

Answer 33

atropine and GTN

Question 34

5-HT3 receptor antagonist mechanism?

Answer 34

block peripheral and central 5-HT3 receptors

Question 35

5-HT3 receptor antagonist uses and examples?

Answer 35

- used to suppress chemo and radiation induced emesis - also used for post op - e.g onsansetron, palonosetron

Question 36

Muscarinic acetylcholine receptor antagonists use?

Answer 36

used for motion sickness

Question 37

Muscarinic acetylcholine receptor antagonists mechanism?

Answer 37

- block muscarinic acetyl choline receptors at multiple sites - causing inhibition of movements and relaxation of the GI tract

Question 38

side effects of Muscarinic acetylcholine receptor antagonists ?

Answer 38

blurred vision, urinary retention, dry mouth, drowsiness

Question 39

Histamine H1 receptor antagonists use?

Answer 39

motion sickness, acute labyrinthitis (inner ear inflam), stomach irritants that cause vomiting

Question 40

Muscarinic acetylcholine receptor antagonists examples?

Answer 40

e.g hyosine, scopolamine

Question 41

Histamine H1 receptor antagonists mechanism?

Answer 41

blockade of H1 receptors in vestibular nuclei and NTS

Question 42

mechanism of Dopamine receptor antagonists?

Answer 42

block dopamine receptors in CTS, exert a prokinetic action on the oesophagus, stomach and intestine

Question 43

examples of Dopamine receptor antagonists ?

Answer 43

domperidone and metaclopramide

Question 44

what is Dopamine receptor antagonists used for?

Answer 44

drug induced vomiting and vomiting in GI disorders

Question 45

what is an NK1 receptor antagonists used with?

Answer 45

used in combo with a 5-HT3 receptor antagonist and dexamethasone

Question 46

when is NK1 receptor antagonists used?

Answer 46

in chemo that makes you very sick

Question 47

example of an NK1 receptor antagonist?

Answer 47

aprepitant

Question 48

Cannabinoid (CB1) receptor agonists used for?

Answer 48

treatment of cytotoxic chemo that is unresponsive to other anti emetics