Pharmacology GI

monogastric means

single stomach

what 4 compartments do ruminants have

rumen, reticulum, omasum, and abomasum

nonruminants consume a plant diet but do not have rumens

for example?

horses

functions or diseases related to the stomach uses the adjective

gastric

functions or diseases related to the small intestines would use the adejctive

enteric

functions or diseases related to the colon would use the adjective

colonic

carnivores are

opportunistic gorgers

what dosage forms are less likely to harm the dog

enteric coating and sustained release

equine GI tract

what is dangerous about an empty stomach for a horse

horses constantly secrete gastric acid so if there is no feed in their stomach it attacks the squamous cells instead and causes gastric ulcers

why should we be cautious of NSAIDs?

they can cause gastric ulcers

why can’t horses vomit

they have a very oblique angle at the connection between the esophagus and the stomach

what other animal cannot vomit due to the oblique angle from the esophagus to the stomach?

rabbit

why should we not fast rabbits?

they can get hepatic lipidosis “fatty liver disease”

they can develop hypoglycemia

the nervous system regulates GI function by the

autonomic nervous system

what is the autonomic nervous system

regulates bodily functions without concious thought

what are the two components of the autonomic nervous system

Parasympathetic nervous system

Sympathetic nervous system

what nerve is associated with the parasympathetic nervous system

vagus nerve X

cranial nerves and nerves in the caudal portion of the spinal cord

what neurotransmitter is associated with parasympathetic nervous system

acetylcholine

what does the parasympathetic nervous system do to the body

decrease HR

constrict pupils

increase digestion

improve blood flow to GI tract

increase gut smooth muscle tone

increase motitility

OVERALL: increase digestion and absorption

what is a name for the parasympathetic system

rest and restore system

what nerves are involved with the sympathetic nervous system

synapse with the chain of ganglia

nerves emerge from the spinal cord at the thoracic and lumbar segments

what is the neurotransmitter associated with the sympathetic nervous system

norepinephrine

the sympathetic nervous system does what to the body

increase heart rate

redirect blood flow from nonessential to essential

decreased perfusion of the intestinal tract

Increased blood pressure

reducing absorption of digested food

decrease gastric and enteric motility

decrease secretion of digestive juices

OVERALL: decreased digestion and absorption of substances

what is the term for the sympathetic nervous system

Fight or Flight system

Locally acting hormones and biologically active compounds

prostaglandins E and I

Histamine

H2 receptors

Oxyntic cells

Gastrin

Bacterial toxins

what are prostaglandins

compounds produced by different tissues in the body to exert change in that immediate area

what do prostaglandins E and prostaglandins I do

increase intestinal mucus and fluid production

decrease gastric hydrochloric acid production

increase intestinal motility

improves blood flow

increases bicarbonate buffers in the mucus layer that protects the stomach

drugs that can block prostaglandins are

anti-inflammatory drugs

what is histamine

released by basophils and mast cells throughout the body during inflammation or allergic reactions

what are H2 receptors

located on parietal cells (oxyntic cells)

produce hydrochloric acid in the stomach

increases gastric acidity

what do overstimulation of H2 receptors do

produce hyperacidity syndrome

results in gastric or duodenal ulcers

what are oxyntic cells

receptors for neurotransmitter acetylcholine

increase stomach acidity

what is the hormone gastrin

signals relaxation of the stomach

increases stomach acidity

what do bacterial toxins do

stimulate sodium and chloride

causes perfuse diarrhea and dehydration

things that influence vomiting reflex

stimulation of neurons from emetic center

stimulation of chemoreceptor trigger zone

inner ear/balance

distention or irritation of the pharynx, stomach, intestines, peritoneum, kidney, gallbladder, or uterus

emotional stimulus or intracranial pressure

stimulation of neurons from the emetic center

contain alpha adrenergic receptors and serotonin receptors

which animal vomits because they are sensitive to sympathetic nervous system stimulation of the alpha receptor

cats

CRTZ stimulation detects ______ in blood and cerebrospinal fluid

toxins

like renal failure, excessive ketones, bacterial toxemia

distention or irritation of GI organs causes what to the body

causes impulses to travel by vagus nerve to the emetic center

hydrogen peroxide is an example of an irritant

what nerve does inner ear/balance associated with

plays on the 8th cranial nerve, vestibulocochlear nerve

what is contradicted with emetic drugs

comatose and seizures

depressed pharyngeal reflexes

shock or dyspnea

strong acid, alkali, volatile liquids ingested

which animals are emetics not used in

rabbits, horses, and some rodents

how much of the stomach contents do we want emetics to remove

no more than 80%

usually 40-60%

what can we give to a dog that hasn’t eaten a lot before giving them hydrogen peroxide to prevent making them sicker

bread

centrally acting drugs

work on the emetic center and CRTZ

stimulates dopamine receptors

includes apomorphine and alpha 2 agonists such as xylazine

locally acting drugs

produce effect by irritating the GI tract

distend the stomach and cause parasympathetic stimulation of the emetic center

apomorphine is a ______ acting drug

centrally

apomorphine characteristics

opioid

used primarily to induce vomiting in dogs

stimulate dopamine receptors in CRTZ

poorly absorbed orally

must be compounded

not a DEA controlled substance

usually given SQ, IV, and conjuctival

what drug reverses the CNS depression and respiratory effects that are happen due to apomorphine

Naloxone

which drug stops vomiting

acepromazine

what animal is apomorphine not used in

cats

it causes morphine mania

IV drug dose for apomorphine in the dog

0\.04 mg/kg

almost immediate response

IM, SC drug dose for apomorphine

0\.08 mg/kg

5-10 min response

conjunctival dose for apomorphine

0\.25 mg/kg

10-20 min response

what is very important to know with apomorphine

wear gloves! because it can irritate your skin if it touches your skin

Xylazine is a ____ acting drug

centrally

what is ylazines reversal drug

yohimbine

what is the dose rate for xylazine

0\.05 mg/kg

dexmedetomidine trade name is

Dexdomitor

dexmedetomidine is a ______ acting drug

centrally

characteristics of dexmedetomidine

alpha 2- adrenergic agonist

not classified as emetic

best used in cats not dogs

stimulates alpha 2 receptors in the CRTZ and vomiting center

Yohimbine, atipamezole, and tolazoline is a reversal for sedative effects not emetic

hydrogen peroxide is a ______ acting drug

locally

causes irritation of gastric mucosa leading to parasympathetic stimulation of emetic center

emetic

what percent hydrogen peroxide do we use

3%

Emetic drugs

apomorphine

xylazine

dexmedetomidine

hydrogen peroxide

sodium chloride

emetic

what is the dose rate for hydrogen peroxide

cats and dogs: 1 ml per pound PO

1 tsp is equal to

5 mls

emetic

what is the max dose for hydrogen peroxide

dogs: 45 mls

cats: 10 mls

emetic

hydrogen peroxide can cause

gastric hemorrhage

emetic

we do not use hydrogen peroxide in

cats unless deemed necessary

emetic

sodium chloride may cause

gastric bleeding. failure to induce vomiting can cause hypernatremia, worsening toxic symptoms

rarely used

antiemetic

phenothiazines are antiemetics that act on the

dopamine antagonist in CRTZ and emetic center

antiemetic

phenothiazines are _____ antagonist

alpha 1

they block compensatory vasoconstriction in peripheral blood vessels

antiemetic

Phenothiazines are good for ____ because they have an antihistamine effect

motion sickness

antiemetic

what is important to know about phenothiazines

antiemetic dose usually is not high enough to prevent vomiting by parasympathetic impulses for GI, peritoneal, visceral stimulation

antiemetic doses generally don’t produce tranquillization

lower seizure threshold in animals prone to seizures

antiemetic

phenothiazines: what are motion sickness drugs

acepromazine, chlorpromazine, and prochlorperazine

antiemetic

phenothiazines: acute gastroenteritis drug

chlorpromazine

antiemetic

antihistamines decrease vestibular apparatus to the emetic center by blocking ________

H1 receptors in the CRTZ

dogs have greater H1 receptors on the CRTZ than cats so ______

antihistamines are more effective in dogs

antihistamines are not very effective in vomiting caused by

parasympathetic stimulation

why are antihistamines not effective in cats

the vestibular signals bypass the CRTZ in cats and travel directly to the emetic center

what are the examples of the antihistamines

diphenhydramine and dimenhyrdrinate

antiemetic

anticholinergics: what do they do

block the effect acetylchloline neurotransmitter

known as antiparasympathetic nervous system drugs

antiemetic

anticholinergic drugs: examples

atropine

aminopentamide (Centrine)

isopropamide

hyoscine

antiemetic

anticholinergics: it is not recommended for

irritable bowel syndrome patients and excessive stimulation of parasympathetic nervous system patients

antiemetic drugs

metoclopramide: _______ __and__ _________ acting

centrally and locally

antiemetic

metoclopramide: what are the centrally acting drug effects

dopamine and serotonin receptor antagonist in CRTZ

Metoclopramide is more effective in

dogs

Antiemetic

Metoclopramide: useful in _______ patients

chemotherapy-induced and other blood-borne vomiting stimulants

antiemetic

metoclopramide: what is important to know

it has to be given in a light sensitive line and you should wrap the syringe

if you puncture the vial and you give it over a long period of time, the light can decrease the concentration

antiemetic

serotonin receptor antagonists: examples

Ondansetron (Zofran)

Dolasetron (Anzemet)

Mirtazapine 5-HT3 and 5HT4 receptor antagonist

antiemetic

serotonin receptor antagonists: Ondansetron (Zofran)

available as injection and oral

thought to be more effective

few side effects more expensive

0\.5 to 1.0 mg/kg PO or 1.0 mg/kg IV

Antiemetic

Serotonin receptor antagonists: Dolasetron (anzemet)

0\.6 - 1.0 mg/g IV, SC, PO

antiemetic

serotonin receptor antagonists: Mirtazapine effect

used more for appetite stimulant but also has antiemetic effect

Antiemetic

Cerenia (Maropitant) effect

neurokinin (NK1) receptor antagonist antiemetic

blocks the action of substance P in the CNS

antiemetic

Cerenia (Maropitant)

what is the difference between injections and tablets

injection: prevention and treatment of acute vomiting in dogs (extra label in cats)

tablets: prevention of acute vomiting and prevention of motion sickness vomiting in dogs (extra label in cats)

antiemetic

Cerenia (Maropitant) technician note

can burn when given as an injection so anticipate this reaction

Antiemetic

Prokinetic: Cisapride definition

used for GI stasis, reflux esophagitis, megacolon (cats)

must be compounded

Antiemetic

Prokinetic: Cisapride need to know

can cause cardiotoxicity when used concurrently why macrolide antibiotics and azole antifungals

Antidiarrheal

Intestinal motility modifiers examples

Anticholinergic drugs: Aminopentamide (centrine)

Narcotics: Diphenoxylate (Lomotil), Loperamide (Imodium)