Vomiting and Diarrhea Flashcards
Purpose of vomiting
- Removal or toxic/irritant material
- Prevention of gastric rupture with obstruction
Vomiting control
-Triggered by brain= emetic center in the medulla
Can be affected by:
-pharyngeal stimulation (H2O2),
-cerebral cortex (fright, pain)
- vestibular system (motion),
-chemoreceptor trigger zone (monitors blood for toxins, alpha2s, apomorphine)
Emetics
-commonly used after ingestion of toxins
*avoid vomiting back up oils or tissue damaging substances
Emetic examples
-Includes apomorphone, hydromorphone, alpha 2 agonists, syrup of Ipecac, Hydrogen peroxide, saturated salt solution
Apomorphine
Dopamine agonist in CRTZ
-90% effective as emetic for dogs but less effective for cats
-administered in eye or IV
-no analgesic or high like other opioids
**other opioids can also induce vomiting- hydromorphone (anesthesia pre med)
alpha 2 agonist as emetic
-emetic for cats
-Xylazine (~50% effective)
-Dexmedetomidine (>50% effective)
Syrup of Ipecac
-GI irritation leading to vomiting
-acts on pharynx receptors
-used in kids, not much in vet med
Hydrogen peroxide
-dogs
-not very effective but clients can do it at home
-acts on pharynx receptors
Saturated salt solution
-used in dogs to make them vomiting
-acts on pharynx receptors
Situations where you want to stop vomiting
-motion sickness
-parvovirus
-gastroenteritis
-chemotherapy
-uremia
-hair balls
Acepromazine
Antagonizes dopamine which inhibits CTZ, other causes
Can also help reduce motion sickness:
-antihistaminic for dogs
-weak anticholinergic in cats
Side effects from Phenothiazine= acepromazine
-hypotension
-sedation
-extrapyramidal signs (aggression)
-lower seizure threshold in epileptics
-prolapsed 3rd eyelid, CYP mediated drug
Extrapyramidal signs
Occurs if excessive inhibition of dopamine receptors
=involuntary movements
**Treat with IV diphenhydramine
Anticholinergics
-block cholinergic afferent pathways from the GI tract and vestibular system to emetic center
-Atropine, scopolamine, propantheline
**works in humans, not really in animals
Antihistamines
-Block both cholinergic (cats) and histaminic (dogs) nerve transmission responsible for transmission of vestibular stimuli to the emetic center
-mild sedation
-diphenhydramine (benadryl) and dimenhydrinate (gravol)
Metroclopramide
-injectable
-was popular in small animals but variable PK
-extrapyramidal effects
Results in:
-at low dose= inhibits dopamine in CNS
-increases gastric and upper duodenal emptying
-high dose: inhibits serotonin in CRTZ
Ondansetron (Zofran)
-expensive
-inhibits 5-HT3 (serotonin) receptors on vagal nerve and CRTZ
-used for chemotherapy emesis (cytotoxic and radiation release of serotonin in small intestines)
-not effective for motion sickness induced vomiting
Maropitant
-Cerenia, Emavert
-oral or injectable
-cats and dogs
-Neurokinin (NK1) receptor antagonist= clocks binding of substance P at emetic center
*can block Apomorphine, and syrup of ipecac vomiting
What is Maropitant labelled for?
Acute vomiting (2mg/kg)
Motion sickness (8mg/kg)
*acepromazine probably still best choice
Adverse effects of cerenia (maropitant)
-can cause bone marrow hypoplasia in young puppies
**be careful with parvovirus
-contraindicated in GI obstructions
Anti emetics for Parvo vomiting
**argue that may not want to stop parvo puppies from vomiting
-can use metoclopramide, ondansetron, maropitant
Maropitant effects other than emetic
-analgesic and anti inflammatory effects
*blocks binding of substance P
Treatment of diarrhea
-fluid therapy
-electrolytes
-acid/base treatment
Fluid therapy for diarrhea
-most important treatment
-used for dehydration and acidosis
-given oral, intravenous, SQ
Electrolyte use for diarrhea
-Replace Na, Cl, and K
Acid/base treatment for diarrhea
Supply animal with bicarbonate to treat acidosis
-metabolize substrates (citrate, propionate, acetate) that produce bicarb
Steps of Oral therapy
Fluids need H2O, Na, and cotransport (glucose or amino acids)!!
-Na transported into mucosa call by Na channels, Na-glucose co transport, Na-amino acid co transport, Na-H exchanger
>Na absorbed and water and Cl will follow
Anti-diarrheal drugs
Protectants and adsorbents
-Kaolin-Pectin (used to have morphine)
-Activated charcoal (absorbs toxins)
-Bismuth subalicylate (pepto-bismol)= Bismuth (coating), aspirin (anti-PGE)
Anticholinergic drugs
Decrease intestinal motility and secretions
BUT few cases of diarrhea are hypermotile. Usually diarrhea is due to slow guts
>systemic side effects and may worsen diarrhea
Hyoscine butylbromide (Buscopan)
-antispasmodic and anticholinergic for horses
-Rapid onset: 5-10mins, duration 3-4hrs
-can cause tachycardia and decreased gut sounds
-Used on label for intestinal pain in non surgical colic
-not very effective
Opioids
-antisecretory and antimotility effects by acting on mu receptors in GI tract
-decreased propulsive intestinal contractions, and increased segmentation= overall constipating effect (COMMON ADR)
-increase GI sphincters tone
-Stimulate absorption of fluid and electrolytes
Loperamine (Imodium)
-opioid with no function on central NS, stays in guts and will bind guts
-used for traveller’s diarrhea
-not really used in vet med. Can’t be used with infectious diarrhea or ABC-B1 deletion dogs
Antimicrobial therapy for diarrhea
Only used for known bacterial causes
**antimicrobials can also cause diarrhea (change in normal flora)
-breakdown of gut can lead to damage and secondary infection/septicemia= antibiotics to help this
**often using antibiotics for the septicemia and not the diarrhea
-use of antimicrobials may result in carrier animals (salmonella and campybacter)
-OTC calf scour boluses= beware! Because they don’t supply fluids, likely won’t work on the actual issue (viral vs. bacteria), will stay in gut and won’t treat septicemia
NSAIDs for diarrhea
-Meloxicam has label claim for calf diarrhea (WITH ORAL FLUIDS)
-Some evidence for use of Ketoprofen (would need higher dose) and Flunixin (only when blood present)
**There is a risk of renal adverse effects with concurrent dehydration
Meloxicam in calves
-increased appetite
-some weight gain
-Therefore helps the animal feel a bit better but no long term effects
Crofelemer
-Conditionally approved use in states for chemotherapy induced diarrhea in dogs
-botanical mixture
-inhibits Cl and Ca channels at enterocytes, and therefore decrease fluid efflux
