GI system Flashcards
what is the GI system and its functions?
the GI system is a long tube responsible for digestion and absorption of nutrients, movement of substances (motility), elimination of waste as feces
what are common CS related to GI?
vomiting, diarrhea, abdominal pain
anatomic GI structures
oral cavity, pharynx, esophagus, stomach, small intestine, large intestine
accessory GI organs
liver, gallbladder, salivary glands, pancreas
what are the 3 types of digestive systems?
monogastric = single simple stomach
ruminant = multichambered forestomach, fermentation breaks down ingested feed before it travels to the true stomach
hindgut fermenters = fermentation in large intestine
peristalisis
wavelike contraction of the longitudinal and circular smooth muscle fibers in the intestinal walls that move food through the gut
segmental contraction
periodic, repeating intestinal constrictions that cause churning of intestinal contents to increase digestion and absorption of nutrients through the intestinal walls
which nervous system controls GI tract activity?
autonomic nervous system (ANS)
what are the two branches of the ANS and what happens if the activity of one branch is blocked?
sympathetic and parasympathetic
blocking activity of 1 branch increases activity of the other branch
cholinergic drugs
parasympathetic drugs
anticholinergic drugs
parasympathetic drugs that inhibit parasympathetic actions
sympathomimetic drugs
stimulate sympathetic branch
other GI helpers
chemical secretions, hormones, digestive enzymes, histamine
antisialogues
saliva stopping drugs
decrease salivary flow
administer IV, IM, SQ to limit excess saliva production during anesthesia
atropine
anticholinergic antisialogue
decreases GI motility and secretions
quick onset and short acting
glycopyrrolate (Robinal)
FDA approved in dogs and cats
doesn’t cross into CNS or placenta
anticholinergic, decreases GI motility and secretions
longer onset and longer acting
antidiarrheals
diarrhea stopping
diarrhea is a symptom of a disease
decrease liquidity of stool, decrease peristalsis, decrease inflammation, improve fecal consistency
what are the causes of diarrhea?
parasitic disease, bacterial infection, viral infection, dietary indiscretion, systemic non-gastrointestinal disease, dehydration, electrolyte imbalance, decreased nutrition uptake
what are the long term effects of diarrhea?
muscle weakness, acid-base disturbance, anorexia
anticholinergic antidiarrheals
treat diarrhea and tenesmus (straining to defecate)
use with caution since they can cause a wide variety of systemic effects
atropine
anticholinergic antidiarrheal
injectable
decreases GI motility
aminopentamide
anticholinergic antidiarrheal
oral, injectable forms
treats acute GI spasms
propantheline
anticholinergic antidiarrheal
tablet form
treats GI spasms and hypersecretion, decreases rectal contractions in horses
N-Butylscopolammonium bromide
IV form
relieves horses of pain due to spasmodic colic, flatulent colic, and simple impactions
adverse effects of anticholinergic antidiarrheals
dry mm, urine retention, tachycardia, constipation
protectant antidiarrheals
coats inflamed intestinal mucosa with a protective layer
adsorbent antidiarrheals
binds to bacteria and/or digestive enzymes and/or toxins to protect intestinal mucosa from their damaging effects
Bismuth subsalicylate
protectant/adsorbent antidiarrheal
coats intestinal mucosa, anti-inflammatory, minor antibacterial effects
don’t use in cats
is a type of subsalicylate (aspirin-like drug, anti-inflammatory)
Kaolin/pectin
protectant/adsorbant antidiarrheal
generic OTC
absorbent and protectant, doesn’t decrease fluid loss, not FDA approved, some can contain bismuth subsalicylate
activated charcoal
protectant/adsorbent antidiarrheal
brand names: Liqui-Char, SuperChar, Actidose-Aqua
powder and liquid forms
absorbs chemicals and drugs in GI tract, not absorbed or metabolized in GI, toxins bind to it and are carried out of GI tract
administered through stomach tube, dosing gun, or syringe
give right after toxin ingestion
toxiban
protectant/adsorbent antidiarrheal
contains activated charcoal and kaolin
di-tri-octahedral smectite (DTO-smectite) (Bio-sponge)
protectant/adsorbent antidiarrheal
not FDA approved, natural clay mineral, used in horses and foals (for diarrhea, colic, antibiotic colic)
binds to toxins produced by bacterial overgrowth
also used in small animal for endotoxemia, enteritis, small intestinal bacteria overgrowth, acute and chronic diarrhea, parvo, food allergies
can be given with Metronidazole
Diphenoxylate
motility reducer antidiarrheal
opioid
C-V controlled with atropine added
decreases intestinal secretions, peristalsis, increases segmental contractions
Loperamide
motility reducer antidiarrheal
opioid
OTC
decreases intestinal secretions, peristalsis, increases segmental contractions, less CNS depression
probiotics
seed the GI tract with beneficial bacteria (such as Lactobacillus spp, enterococcus faecium, Bifidobacterium spp)
mechanisms of action: decreases pathogenic
probiotics mechanisms of action
decreases pathogenic bacteria survival by competing for nutrients and colonizing sites, produces antimicrobial factors, alters microenvironment, decreases local inflammation, alters immune responses
Metronidazole
antibiotic antidiarrheal
effective against anaerobic bacteria, effective against protozoa, has anti-inflammatory effects
constipation
passage of feces is slowed producing infrequent stool that is often dry and hard
obstipation
difficult to manage constipation often leading to the inability to evacuate an impacted mass of dry hard feces
colic
in horses
abdominal pain that may be caused by a number of underlying gut problems such as intestinal distention due to gas, constipation, bowel obstruction with sand or feed, or torsion of intestines
laxative
medicine that loosens the bowel contents and encourages evacuation of stool
cathartics
harsher laxatives that result in a soft to watery stool and abdominal cramping
how do osmotic laxatives work?
aka hyperosmolar
work by pulling water into the colon by osmosis
composed of salts or saline, lactulose, and glycerin
Lactulose
osmotic laxative
oral syrup
treats hepatic encephalopathy
metabolized by bacteria in the colon to form low osmotic acids that pull fluid into the colon
sodium phosphate with sodium biphosphate
osmotic laxative
used for enemas
not for cats, causes hyperphosphatemia and hypocalcemia
Magnesium sulfate
osmotic laxative
contain epsom salts
used for enemas
Magnesium hydroxide
osmotic laxative
Carmilax-powder, Magnalax, Poly Ox II Bolus
oral
Polyethylene glycol (PEG)
electrolyte solution
used for enemas
stimulant laxatives
stimulant = irritant or contact
increases peristalsis by chemically irritating sensory nerve endings in the intestinal mucosa
not approved for vet
Castor oil
stimulant laxative
ricinoleic acid, inhibits water and electrolyte absorption causing fluid accumulation in GI tract, increases peristalsis
Bisacodyl
stimulant laxative
cathartic
enteric coated tablets, suppository, don’t give within an hour of milk or antacids
Senna, Senokot
stimulant laxative
similar to other drugs in this group
bulk forming laxatives
natural fibrous substances or semisynthetic compounds
added to diet, absorbs water into intestine, increases fecal bulk, stimulates peristalsis
examples of bulk-forming laxatives
psyllium hydrophilic mucilloid (equine psyllium), calcium polycarbophil, Bran
emollient laxatives
stool softeners, lubricants, fecal wetting agents
Docusate calcium
emollient laxative
regular and soft gel capsules
Docusate sodium, docusate sodium sulfasuccinate (DSS) (Pet-Ema, Docu-soft)
emollient laxative
petroleum white petrolatum, mineral oil (CatLax, Laxatone)
prevents and treats hairballs, mineral oil for colic in horses
antiemetics
control vomiting
commonly used with other treatment to help alleviate discomfort and control electrolyte balance
phenothiazine derivative antiemetics
antiemetic group
decreases the stimulation to vomit
thought to lower seizure threshold
causes vasodilation and hypotension
don’t use in abnormal GI motility patients
Acepromazine (PromAce and generic)
phenothiazine derivative antiemetic
injectable and oral tablets
FDA approved for motion sickness
Prochlorperazine
phenothiazine derivative antiemetic
injectable, tablet, suppository
Chlorpromazine
phenothiazine derivative antiemetic
injectable, tablet
antihistamines
antiemetic group
controls vomiting due to motion sickness, vaccine reaction, inner ear problems
doesn’t work for vomiting cats
ex: Diphenhydramine, Dimenhydrinate, Meclizine
Metoclopramide
antiemetic
works centrally by blocking CRTZ (vomiting zone)
and works peripherally by speeding gastric emptying and strengthening sphincter tone
oral, SQ, IV, IM
most effective as CRI
not used in animals with GI obstructions, GI perforation, hemorrhage
serotonin receptor antagonist
antiemetic group
blocks serotonin receptors that cause vomiting
Ondansetron
serotonin receptor antagonist antiemetic
oral dissolving tablet, injectable, oral solution
Dolasetron
serotonin receptor antagonist
IV, tablet
Granisetron
serotonin receptor antagonist
oral tablet and solution, transdermal patch, SQ
Maropitant
antiemetic group
inhibits neurotransmitter involved in vomiting
Maropitant citrate (Cerenia)
Maropitant anitemetic
vet approved for dogs and cats
suppresses peripherally and centrally induced vomiting
oral, IV, SQ
emetics
induce vomiting
used for poisonings or drug overdoses
Apomorphine
centrally acting emetic
dopamine agonist
directly stimulates CRTZ
very effective in dogs, not very effective in cats
SQ, IV, topical
works in 5-10 minutes
Xylazine (Rompun, AnaSed)
centrally acting emetic
vomiting inducer in cats as a side effect
do we usually use peripherally acting emetics?
no they’re not usually used or recommended because they aren’t reliable
Hydrogen peroxide (3%)
peripherally acting emetic
gastric irritant
apply to back of pharynx to stimulate nerve that induces vomiting
give 5-10 mL orally by syringe
can cause aspiration pneumonia
don’t use for cats because it can cause hemorrhagic gastritis
salt
peripherally acting emetic
be careful of sodium overdose
used for cerebral enema
can be fatal
powdered mustard
peripherally acting emetic
not effective
inhaled and can cause lung damage
how do gastric ulcers develop?
when there is an excess of harmful substances which lead to erosions in the stomach/small intestine lining
antiulcer drugs
help treat/prevent ulcer formation
antacids
antiulcer group
promote ulcer healing by neutralizing HCl and pepsin activity
can bind to other drugs or increase stomach pH
types: systemic or local
Magnesium hydroxide (Magnalax)
antacid antiulcers
treats rumen acidosis
Aluminum hydroxide/magnesium hydroxide
antacid antiulcers
adjunctive treatment for gastric ulcers in dogs and foals
histamine-2 receptor antagonists
antiulcer group
inhibits acid production
take with or without food
extra-label
Cimetidine
histamine-2 receptor antagonist antiulcer
decreases gastric acid secretion
tablet, oral solution, injectable
given every 8 hours
Ranitidine
histamine-2 receptor antagonist antiulcer
more potent, longer duration, stimulates gastric emptying and intestinal motility
given 12 hours
Famotidine
histamine-2 receptor antagonist antiulcer
more potent, fewer AE
coated tablets, oral powder, injectable
given every 24 hours
Nizatidine
histamine-2 receptor antagonist antiulcer
increased GI motility
tablet, capsule, solution
given every 24 hours
Sucralfate
mucosal protective antiulcer
stomach mucosal protectant
covers and protects ulcers
1g tablets (give as a slurry)
don’t give with other drugs
treats esophagitis, gastric/duodenal ulcers, uremic gastritis
Misoprotal
protaglandin analog antiulcer
suppresses gastric acid production, increases mucous production, protects gastric ulcers from NSAIDs
tablet
not used in pregnant animals
proton pump inhibitors
antiulcer group
binds to proton pumps and inhibits gastric acid production
most effective 30 minutes before a meal
Omeprazole (Gastrogard, Ulcergard)
proton pump inhibitor antiulcer
only PPI that is FDA approved for dogs and cats
safe for horses and foals over 4 weeks
prevents and heals gastric ulcers
Lansoprazole
proton pump inhibitor antiulcer
oral or IV
treats gastric reflux, heals ulcers, less likely to react to other drugs
Esomeprazole
proton pump inhibitor antiulcer
oral or IV
treats gastroduodenal ulcers, prevents and treats gastric erosions from ulcer-producing drugs
antifoaming agents
surfactants = decreases or prevents formation of foam
used in ruminants with frothy bloat
breaks down foam which allows gas release through belching
Poloxalene and polymerized methyl silicone
antifoaming agent
administered as a solution through a stomach tube
prokinetic agents (motility enhancing)
increases GI motility, enhances movement of material through GIT, treats gastric paresis, treats megacolon
parasympathetic (cholinergics) prokinetic agents
increase motility and secretions, relaxes sphincters
Neostigmine
cholinergic prokinetic agents
treats rumen atony in ruminants, increases motility in horses, diagnoses myasthenia gravis in dogs
Dexpanthenol (d-panthenol injectable)
cholinergic prokinetic agent
treats intestinal distention or atony, paralytic ileus, colic
dopaminergic antagonists
prokinetic agent group
increases tissue sensitivity to acetylcholine
stimulates gastroesophageal sphincter tone, stomach motility, intestinal motility
Metoclopramide
dopaminergic antagonist prokinetic agent
antiemetic
Domperidone (Equidone gel)
dopaminergic antagonist prokinetic agent
less neurologic effects, doesn’t cross blood brain barrier
FDA approved for treatment of fescue toxicosis in periparturient mares
Cisapride
prokinetic agent group
serotonergic agent
stimulates motility of the stomach, small intestine, and colon
treats constipation, gastroesophageal reflux, ileus
pancrelipase (Viokase-V powder, Pancrezyme)
enzyme supplements
tablet or powder mixed with food
lipase digests fats
amylase digests starches
protease digests proteins
treats exocrine pancreatic insufficiency (EPI)
exocrine pancreatic insufficiency (EPI)
pancreas doesn’t produce sufficient enzymes
symptoms: fatty/greasy diarrhea, weight loss, vomiting
Orexigenic drugs
appetite stimulants
Capromorelin (Entyce)
orexigenic
FDA approved for dogs, extra-label for cats
stimulates receptors in the hypothalamus to induce hunger
oral solution which is shaken
Elura (Capromorelin)
orexigenic
version of Capromorelin that is FDA approved for cats
Mirtazapine (Mirataz)
orexigenic
antidepressant that causes appetite stimulation and antiemetic properties
human approved tablets used extra-label for dogs and cats
Mirtazapine ointment is FDA approved for cat transdermal
caution with severe liver or kidney disease patients
Cyproheptadine
orexigenic
human approved phenothiazine
inhibits “feeling full” receptors
Benzodiazepines
orexigenic
cats
induces GABA, inhibits satiety center in hypothalamus
Diazepam
Benzodiazepine orexigenic
used most often
IV, IM, oral
avoid in liver disease cats
Oxazepam
Benzodiazepine orexigenic
oral
not metabolized in the liver
Glucocorticoids
orexigenics
Prednisolone: causes euphoria that increases appetite, not for long term use
Propofol: hypnotic drug, stimulates appetite in dogs at low doses
