Gastric ulcers, bloat, colic and constipation

Question 1

what does the gastric mucosa need protecting from?

Answer 1

pepsin, acid and refluxed instestinal proteases and bile salts

Question 2

how are gastric ulcers caused?

Answer 2

disruption of the mucosal barrier leading to back-diffusion of acid etc into the mucosa that initiates and perpetuates inflammation

Question 3

what are the 5 components of the mucosal barrier?

Answer 3

epithelia, mucus-bicarbonate layer, cytoprotection, mucosal blood supply and restitution and epithelial renewal

Question 4

describe the mucus-bicarbonate layer

Answer 4

mucus secreted by epithelium contains bicarbonate. acts as a barrier and maintains surface pH of 6

Question 5

describe the epithelium

Answer 5

very resistant to acid - extremely low perm to water and protons, tight junctions etc

Question 6

what is cytoprotection?

Answer 6

PGEs mediate production of mucus, increase secretion of bicarbonate, regulate blood flow and maintain epithelial growth

Question 7

what is significant about the mucosal blood supply?

Answer 7

high flow rate so washes any diffused acid away and direction of flow from crypts (where H+ and HCO3 produced) to surface brings supply of HCO3 to the surface

Question 8

what is significant about restitution and epithelial renewal?

Answer 8

migration of adjacent cells to heal small areas.

epithelium has a high replication rate

Question 9

what is the most common cause of gastric ulcers? (SA)

Answer 9

NSAIDs direct toxicity and non-selective inhibition of COX1 (produces PGEs)
use NSAIDs with high COX2:COX1 ratio

Question 10

what are acid blockers used for?

Answer 10

to treat oesophageal and gastric ulcers

Question 11

Give 3 types of acid blockers

Answer 11

antacids, H2 antagonists and proton pump inhibitors

Question 12

give examples of antacids and describe their properties

Answer 12

AlOH, MgCO3, CaCO3. available over the counter, effective and safe for neutralising acid. also decrease pepsin activity, bind bile salts and stimulate bicarbonate secretions.

can get rebound hyperacidity

Question 13

give an example of a licensed H2 agonist

Answer 13

Cimetidine - block H2 receptors so prevent acid secretion. can be given orally/ parenterally
Can have steroid hormone SE (drug interactions CP450)

Question 14

describe some non-licensed H2 antagonists

Answer 14

e.g. ranitidine and famotidine. do not have SE of cimetidine, more potent allowing less frequent doses.

some also prokinetic

Question 15

how do proton pump inhibitors work?

Answer 15

irreversibly bind to the proton pump so very potent acid inhibitors. after 5 doses acid secretion abolished.
gastroguard used in horses but unsuitable for C/D
omeprazole used instead. others available

Question 16

what 2 types drugs are used as mucosal protectants?

Answer 16

sucralfate and PGEs

Question 17

describe how sucralfate works

Answer 17

available as tablets/ suspension. aids healing by forming ppt and binding to damaged tissue providing a barrier. also other beneficial effects - inactivates pepsin, binds to bile acids, stimulates PGE syn, stimulates epithelia proliferation.
SE - constipation occasionally
give separately to H2 antagonists as may reduce each others efficacy

Question 18

how do PGEs work?

Answer 18

cytoprotective - increases mucus secretion, blood flow, HCO3 secretion, decreased acid secretion and maintains epithelial growth

Question 19

give an e.g. of a synthetic PGE

Answer 19

misoprostol. effective in dogs against NSAID ulceration. no effective at healing existing ulcers
causes abortion - NOT TO BE USED IN PREGNANCY

Question 20

what is bloat? (ruminants)

Answer 20

life-threatening accumulation of free gas/ foam.
gas eliminated by stomach tube/ flank trocharisation
foam needs agents to break down - turpentine, sunflower oil/ surfactants to reduce surface tension of bubbles e.g. poloxalene/ silicones

Question 21

what is colic?

Answer 21

abdominal pain caused by intestinal diseases

Question 22

what is the treatment for colic

Answer 22

surgery, fluid therapy, analgesia, lubricants, laxatives, anti-spasmodics, sedation, preventative worming etc

Question 23

what is constipation?

Answer 23

infrequent defecation with excessively dry or hard faeces and increased straining to defecate.

Question 24

list causes of constipation

Answer 24

dietary and environmental, painful defecation, neuromuscular disease, debility, obstruction

Question 25

how would you treat constipation?

Answer 25

correct underlying cause, laxative to soften faeces allowing easier passage, prokinetics to stimulate motility, enemas, bul-forming substances e.g. bran (fibrous diet)

Question 26

give examples of laxatives

Answer 26

osmotic e.g. lactulose, lubricants e.g. liquid paraffin, surfactant e.g. docusate

Question 27

give examples of prokinetics

Answer 27

cisapride, ranitidine

Question 28

stimulants?

Answer 28

castor oil, danthron

Question 29

enemas?

Answer 29

warm soapy water safest. also phosphate (fleet - can cause hyperphosphataemia in C/ small dogs)