pharmacological basis for treatment of GI disorders Flashcards
what is gastrin
peptide hormone that is secreted by gastric mucosa and duodenum
what does gastrin secrete
gastric secretion
blood flow
gastric motility
what is gastrin release controlled by
NTs and mediators like milk/ca2+ solutions
action of Ach in the GIT
NT - Stimulates mACh receptors on parietal cells and on histamine containing cells
action of histamine in GIT
local hormone - acts on H2 receptors on parietal and mast cells - - its release can be increased by gastrin and Ach
what do PGE2 and PGI2 do
inhibit acid secretion
effect of Dopamine on the gut
direct relaxant effect - activates D2 receptors in LOS and fundus and antrum of stomach
what does dopamine inhibit the release of
Ach
what is metoclopramide used for
GI reflux
what does mteoclopramide do
stimulate gastric motility
accelerate gastric emptying
how does metoclopramide promote gut motility
- 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
what can metoclopramide also be used for
treatment of migraines in ER
uses for antispasmodic agents
IBS, diverticulitis
examples of antispasmodics
propantheline, dicyclomine,
how do antispasmodics work
dec bowel spasm
relax GIT smooth muscle
- muscR antagonists - inhibit PSNS activity, reducing spasm
goals of drug intervention in gastric ulcer
reduce acid secretion - H2 receptor antagonists
neutralise secreted acid - antacids
attempt at h pylori eradication
drugs can be used to inhibit/neutralise gastric acid secretion for what conditions
peptic ulcer
reflux oesophagitis
zollinger-ellison syndrome - gastrin producing tumour
general mechanism of antacid action
neutralise gastric acid
increase pH of gastric acid - peptic activity stops at pH = 5
how does bismuth chelate have cytoprotective effects
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
side effects of bismuth chelate
blackens stool and tongue
examples of H2 receptor antagonists
ranitidine, cimetidine
what do h2 receptor antagonists do in the GIT
inhibit acid secretion stimulated by
histamine
ach
gastrin
what are h2 receptor antagonists used to treat
peptic ulcer,
reflex oesophagitis
problems with h2 receptor antagonists
promote healing of duodenal ulcers, but if you stop treatment, you relapse
how do prostaglandins protect the stomach mucus
stimulate secretion of bicarb
reduce proton secretion
promote vasodilation
why do nsaids cause gastric bleeding
inhibit pg synthesis
example of proton pump inhibitors
omeprazole, lanzoprazole, rabeprazole
clinical used of PPIs
peptic ulcer
reflux oesophagitis
zollinger-ellison syndrome
mechanism of action of PPIs
weak bases inactive at neutral pH - irreversibily inhibit H/K ATP-ase pump
decreased basal and food stimulated gastric acid secretion
