pharmacological basis for treatment of GI disorders

Question 1

what is gastrin

Answer 1

peptide hormone that is secreted by gastric mucosa and duodenum

Question 2

what does gastrin secrete

Answer 2

gastric secretion
blood flow
gastric motility

Question 3

what is gastrin release controlled by

Answer 3

NTs and mediators like milk/ca2+ solutions

Question 4

action of Ach in the GIT

Answer 4

NT - Stimulates mACh receptors on parietal cells and on histamine containing cells

Question 5

action of histamine in GIT

Answer 5

local hormone - acts on H2 receptors on parietal and mast cells - - its release can be increased by gastrin and Ach

Question 6

what do PGE2 and PGI2 do

Answer 6

inhibit acid secretion

Question 7

effect of Dopamine on the gut

Answer 7

direct relaxant effect - activates D2 receptors in LOS and fundus and antrum of stomach

Question 8

what does dopamine inhibit the release of

Answer 8

Ach

Question 9

what is metoclopramide used for

Answer 9

GI reflux

Question 10

what does mteoclopramide do

Answer 10

stimulate gastric motility

accelerate gastric emptying

Question 11

how does metoclopramide promote gut motility

Answer 11

• inhibits pre/post-synpatic D2 receptors
• stimulates presynaptic excitatory 5-HT4 receptors
• antagonist for presynaptic inhibition for mAchRs, inc. ach release - lowers LOS and gastric tone, improves antroduodenal coordination, accel. gastric emptying

Question 12

what can metoclopramide also be used for

Answer 12

treatment of migraines in ER

Question 13

uses for antispasmodic agents

Answer 13

IBS, diverticulitis

Question 14

examples of antispasmodics

Answer 14

propantheline, dicyclomine,

Question 15

how do antispasmodics work

Answer 15

dec bowel spasm
relax GIT smooth muscle
- muscR antagonists - inhibit PSNS activity, reducing spasm

Question 16

goals of drug intervention in gastric ulcer

Answer 16

reduce acid secretion - H2 receptor antagonists
neutralise secreted acid - antacids
attempt at h pylori eradication

Question 17

drugs can be used to inhibit/neutralise gastric acid secretion for what conditions

Answer 17

peptic ulcer
reflux oesophagitis
zollinger-ellison syndrome - gastrin producing tumour

Question 18

general mechanism of antacid action

Answer 18

neutralise gastric acid

increase pH of gastric acid - peptic activity stops at pH = 5

Question 19

how does bismuth chelate have cytoprotective effects

Answer 19

protects gastric mucosa - forms a barrier over the crater of the ulcer and adsorbs pepsin, and increases HCO3 and PG secretion - AND toxic against h pylori

Question 20

side effects of bismuth chelate

Answer 20

blackens stool and tongue

Question 21

examples of H2 receptor antagonists

Answer 21

ranitidine, cimetidine

Question 22

what do h2 receptor antagonists do in the GIT

Answer 22

inhibit acid secretion stimulated by
histamine
ach
gastrin

Question 23

what are h2 receptor antagonists used to treat

Answer 23

peptic ulcer,

reflex oesophagitis

Question 24

problems with h2 receptor antagonists

Answer 24

promote healing of duodenal ulcers, but if you stop treatment, you relapse

Question 25

how do prostaglandins protect the stomach mucus

Answer 25

stimulate secretion of bicarb
reduce proton secretion
promote vasodilation

Question 26

why do nsaids cause gastric bleeding

Answer 26

inhibit pg synthesis

Question 27

example of proton pump inhibitors

Answer 27

omeprazole, lanzoprazole, rabeprazole

Question 28

clinical used of PPIs

Answer 28

peptic ulcer
reflux oesophagitis
zollinger-ellison syndrome

Question 29

mechanism of action of PPIs

Answer 29

weak bases inactive at neutral pH - irreversibily inhibit H/K ATP-ase pump
decreased basal and food stimulated gastric acid secretion