Gastrointestinal (year 2) Flashcards
what can lead to electrolyte/fluid imbalance in the GI tract?
vomiting and obstructed pylorus
what non-specific therapy used to correct fluid/electrolyte imbalances?
parenteral fluid therapy
name 4 classes, with examples, of drugs used for pain management
NSAIDS - dipyrone, phenylbutazone
Opioids - morphine, butorphanol
Sedative - xylaxine, detomidine
Anti-spasmodic - hyoscine
what class of drugs are used in the management of acid secretion and ulcers?
antacids
what is the role of antacids?
inhibit acid secretion, neutralise existing acid, coat/protect gastric mucosa
give two groups of drugs that inhibit acid secretion with examples
histamine2 blockers - cimetidine, rantidine
proton pump inhibitors - omeprazole
how do proton pump inhibitors work?
irreversibly binds to hydrogen potassium ATPase pump
name a locally acting antacid
aluminum and magnesium salts
how do locally acting antacids work?
neutralise luminal acid, inhibit pepsin cleavage, act as adsorbents, stimulate prostaglandins to enhance mucosal barrier protection
name a gastric protectant that can be given
sucralfate
what is sucralfate and how does it work?
viscous gel at pHs less than 4, binds to ulcerated proteins to protect from acids and pepsin
what are the drugs called used to stimulate vomiting?
emetics
name the four stimuli of vomiting
chemoreceptor trigger zone via dopaminergic input
chemoreceptor trigger zone and vomiting centre via substance P binding to neurokinin1 (NK1) receptors
vagal/sympathetic afferent pathways of GI tract
vestibular apparatus via cholinergic/histaminergic afferent pathways
what animals have a well defined vomiting reflex?
carnivores and omnivores
name some animals with a poorly developed vomiting reflex
cow, horse, rat, rabbit
when may emetics be used?
induce vomiting after toxin ingestion or prior to anaesthesia
name a centrally acting emetic
apomorphine - stimulate chemoreceptor trigger zone
name a peripherally acting emetic
sodium chloride or bicarbonate of soda - stimulate vagal/sympathetic afferent receptors in pharynx/stomach
name the group of drugs used to prevent vomiting
anti-emetics
why would you want to use an anti-emetic?
vomiting leads to electrolyte and acid/base imbalances along with dehydration
why must diagnosis be confirmed before using an anti-emetic?
they may be contraindicative if used when there is a gastric/intestinal obstruction
what are the 4 drug groups used as anti-emetics?
anti-histamines, anticholinergics, antidopaminergic agents, NK1 antagonists
give examples of anti-histamines and how they work when used as an anti-emetic
diphenylhydramine, promethazine - block histaminergic and cholinergic afferent pathways from vestibular organs to the vomiting centre
give examples of anti-cholinergic and explain how they work when used as anti-emetics
propantheline - block cholinergic afferent pathways from the GI tract to the vomiting centre
name the two drugs used as antidopaminergic agents for anti-emetic use
phenothiazines and metoclopramide
how do phenothiazines work as anti-emetics?
block dopamine receptors in chemo-receptor trigger zones and when used at high doses it can block those in the vomiting centre
how does metoclopramide work as an anti-emetic?
blocks dopaminergic receptors in the chemo-receptor trigger zone, also able to stimulate GI motility
name an NK1 antagonist used as an anti-emetic
maropitant
how does maropitant work as an anti-emetic?
binds to receptors in the chemo-receptor trigger zone and vomiting centre to block the binding of substance P
what are the uses for laxatives/cathartics?
relief of non-dietary acute constipation, removal of toxic ingestants, prevent tenesmus, evacuation of bowl for surgery/radiography
what is tenesmus?
cramping rectal pain
what are the two classes of cathartics?
osmotic and irritant
what are some examples of osmotic cathartics?
lactulose, magnesium sulphate (Epsom salts), sodium sulphate, polyethylene glycol
how do osmotic cathartics work?
they are non-absorbable so draw water into the lumen of the gut causing distention which stimulates contractions
give an example of a irritant cathartic
caster oil
name some laxatives
ispaghula and sterculia
how do laxatives work?
contain hydrophobic colloids that absorb water and increase the ingest bulk to stimulate peristalsis
give an example of a lubricant used as a laxative/cathartic
paraffin oil
give an example of a surfactant used as a laxative/cathartic
docusate
how do surfactants work as laxatives/cathartics?
hydrate and soften faeces by emulsifying actions
during diarrhoea what needs to be correct and how?
dehydration by oral rehydration therapy using glucose/amino acids to enhance water uptake and electrolytes to correct any imbalances
what are three classes of drugs used as antidiarrhoeals?
protectants/adsorbents, opiates, anti-cholinergic agents
how to protectants/adsorbents work? give examples of them
adsorbs toxins and provides protective coating to inflame mucosa. also stimulate prostaglandin and bicarbonate secretions - bismuth salts, kaolin-pectin
how do opiates work as anti-diarrhoeals? give examples of them
inhibit acetylcholine release increase segmental contractions to slow transit and allow more water absorption - loperamide and codeine
how do anti-cholinergic agents act as anti-diarrhoeals?
inhibit propulsive and non-propulsive GI motility
what is anorexia?
when an animal won’t eat
what non-pharmacological ways can an animal be encouraged to eat?
warm palatable food and liquid enteral alimentation
give examples of drugs used as appetite stimulants
benzodiazepines (diazepam, oxazepam), cyroheptadine, glucocorticoids (prednisolone, dexamethasone)
how do benzodiazepines work to stimulate appetite?
increase GABA - leading to anti-serotonergic effect depressing the satiety centre in the hypothalamus
how does cyroheptadine work to stimulate appetite?
it is a serotonin and histamine antagonist suppressing the satiety centre in the hypothalamus
what are probiotics?
sample of normal intestinal flora
what are probiotics?
substrates that promote normal intestinal microbes
name 4 drugs specifically used as bowel anti-inflammatories
sulfasalazine, olsalazine, tylosin, metronidazole
how does sulfasalazine work?
cleaved by bacteria to sulphapyridine and salicylate, the salicylate has anti-inflammatory effects
how does olsalazine work?
cleaved by bacteria to salicylate, the salicylate has anti-inflammatory effects, doesn’t contain sulphapyridine so is less toxic than sulfasalazine
how does tyrosine work?
surpasses bacteria overgrowth by inhibiting protein synthesis in them
how does metronidazole work?
anti-protozoa and anti-bacterial so suppresses cell mediated immune reaction s
what are are 4 main drug groups used for the management of pancreatic and liver disease?
digestants, urso-deoxycholic acid, lactulose, hepato-biliary cytoprotective agenst
name two digestants
pancreatic enzyme supplements and bile acid/salts
what are pancreatic enzyme supplements used to treat?
exocrine pancreatic insufficiency
what do pancreatic enzyme supplements contain?
lipase, amylase, protease that are usually administered with acid inhibitors to prevent destruction of enzymes
how do bile acid work?
stimulate the flow of bile
how do bile salts work?
emulsify dietary lipids to enhance the digestion and absorption
what are urso-deoxycholic acids used to treat?
cholestatic liver disease in which bile acids build up in the body, the hydrophobic bile acids are toxic to hepato-biliary cell membranes
how do urso-deoxycholic acids work?
it is a hydrophilic bile acid that inhibits the ideal absorption of hydrophobic bile acids. acts as a cyto-protective of the biliary system
when is lactulose used?
used for patients with hepatic encephalopathy to reduce the blood anaemia levels as the acid traps ammonia and ammonium ions that are egested
what happens to lactulose when in the body?
metabolised by colonic bacteria into organic acids (lactic, formic, acetic) that aren’t well absorbed and trap ammonia and ammonium ions
name three hepato-biliary cytoprotective agents
S-adenosylmethionine, silymarin, vitamin E
how does S-adenosylmethionine work?
antioxidant used to stabilise membrane function and modulate cytokine expression
how does silymarin work?
it is a reactive oxygen species scavenger that increases hepatic protein synthesis and bile secretions. also works as an anti-inflammatory and antifibrotic
what is vitamin E used as?
antioxidant and anti-inflammatory
what is the chemical name for vitamin E?
tocopherol
what is an important consideration when giving oral medication to young calves/lambs?
oesophageal groove must be stimulated to ensure the drug bypasses the developing g rumino-reticulum
what is the pH of the rumen needed for efficient fermentation?
5.5-7
what are two requirements of the rumen microbes?
proper nutrient intake and normal gut motility
what is the extrinsic and intrinsic innervation of the ruminants GI system?
extrinsic - vagal
intrinsic - enteric nervous system
how can you stimulate the closure of the oesophageal groove to allow bypass of the rumino-reticulum and passage of drugs into the abomasum and small intestine?
warm milk, copper sulphate, sodium bicarbonate
what are cholinergics used for when restoring rumen function?
to increase the frequency of contractions
what drug can be administered parenterally to stimulate extrinsic contractions when restoring rumen function?
opiate antagonists
what can be done to introduce more healthy bacteria and protozoa into the rumen?
rumen transfer of fluids from a viable patient
give two examples of rumen antacids and what they are used for
aluminium hydroxide and calcium carbonate used to treat mild cases of rumen acidosis
what is used to treat more severe cases of rumen acidosis?
parenteral fluid therapy and/or evacuation of the rumens contents
give examples of products able to be used as rumen acidifiers
vinegar and acetic acid
when may rumen acidifiers be used?
treat excess bicarbonate influx from hyper-salivation or in acute area poisoning to convert ammonia into ammonium to reduce absorption
what are viscosity altering agents used for?
anti-bloat
give an example of anti-bloat agents and how it is used
mineral/vegetable oil to treat frothy bloat by altering the surface tension of bubbles and allowing them to break up
what is colic?
abdominal pain of the GI tract
what defines the difference between surgical and medical colic?
if the pain can be managed then it is medical
what drugs can be given to manage pain?
NSAIDs - phenylbutazone and flunixin meglumine
opiates - butorphanol
how long do the drugs used to manage pain work for and when are they used?
phenylbutazone - short acting for mild pain
flunixin meglumine - long acting for severe pain so may mask signs
butorphanol - short acting for moderate pain
name the three medical colics
spasmodic, pelvic flexure impaction and flatulent
what is spasmodic colic and how is it treated?
hypermotility of the small intestines treated by anti-spasmodics such as butylscopolamine and analgesics
how does butylscopolamine work?
inhibits M1 muscarinic acetylcholine receptors
what is pelvic flexure impaction colic and how is it treated?
impaction of the narrowing between left ventral and right dorsal colon treated with oral fluid for lubrication/softening on impaction
what is flatulent colic and how is it treated?
build up of gas causes distention treated with pain management using opioids
