GIT

Emetics

Induce vomiting

Antemetics

prevent vomiting

Antiulcers

for the management of gastric ulceration

Antidiarrheals

Protectants

Antispasmodics

For the management of diarrhea

Laxatives

Promote defecation

Prokinetics

Increase GIT Motility to enhance the transit of material

Antifoaming agents

For the treatment of frothy bloat in ruminants

Anti-inflammatory drugs

Used in the treatment of inflammatory bowel disease

Antibiotics

Specific antibacterial/antiprotozoal effect

Digestive enzymes

Aid in fat, carbohydrate and protein digestion

probiotics

beneficial bacteria for maintenance or restoration of gut health

appetite stimulants

stimulate an animal to eat

Emesis (vomition)

forceful involuntary expulsion of stomach contents

a manifestation of a large number of conditions, many of which are not primary disorders of the GIT

prevents absorption of noxious substances

serious consequences of emesis

acid-base imbalance

electrolyte depletion

malnutrition

aspiration pneumonia

Bilateral vomition centers

 reticular formation of the medulla integrate signals from a large number of outlying sources and their excitement is ultimately what triggers vomition.

The vomiting center receives afferent signals from the ff. locations:

GIT

Extra GIT

Extra Medullary

Chemoreceptor trigger zone

Chemoreceptor trigger zone (CRTZ)

Location: area postrema in the lateral wall of the fourth ventricle

CRTZ contains the ff receptors

• Dopaminergic (D₂)

• 5-hydroxytryptamine (5-HT₃, serotonin)

• Cholinergic (M₁₎)

• Substance P (NK1)

Centrally acting emetics

MOA: stimulate the CRTZ, which in turn excites the vomiting center

examples of centrally acting emetics

Apomorphine

Xylazine

Apomorphine

An opiate

Dopamine receptor agonist

Used as an emetic in dogs (induces vomiting within 5-10 min of IM injection)

causes CNS stimulation in cats

Xylazine

• a₂-adrenergic agonist with sedative-analgesic action

• A reliable emetic in cats (induces vomiting within 3-5 min)

• Monitor the animal for sedation & hypotension

Locally acting emetics

MOA: stimulate directly the pharynx that triggers the vomiting center via CN IX or the visceral afferent nerves of the stomach & intestines by causing irritation, inflammation or distention

3% Hydrogen Peroxide

• Has a direct irritant effect on the oropharynx and gastric mucosa

• Dosage: 5 ml/5 lb (not to exceed 45 ml), repeat if unsuccessful on the 1^st attempt

• Aspiration of H₂O₂ foam causes severe aspiration pneumonia (administer cautiously!)

• Induces vomiting in dogs, cats, pigs and ferrets

Why do we use Antiemetics drug?

Prevent exhaustion, dehydration, acid-base & electrolyte disturbances & aspiration pneumonia

Use for not more than 3 days

Antiemetics are best given in this route

parenterally

Antihistamines

• Block H₁ receptors in the vestibular apparatus & CRTZ

• For vomiting in dogs and cats due to motion sickness or inner ear abnormalities

• e.g. Diphenhydramine, Dimenhydrinate, Promethazine, Meclizine (extralabel use in dogs)

Adverse side effect: may cause sedation

Phenothiazine tranquilizers

• Block the D₂ receptors in the CRTZ & inhibit the the vomiting center

• May be used to prevent motion sickness in dogs and cats

• e.g. Chlorpromazine, Prochlorperazine

• Adverse side effects: hypotension and sedation

Serotonin (5-HT3) receptor antagonists

• Inhibit 5HT₃ receptors in the CRTZ

• e.g. Ondansetron & Dolasetron, Granisteron 

• Ondansetron is recommended in dogs receiving chemotherapy

• Ondansetron is not effective for emesis caused by motion sickness

Metoclopramide

• D₂ receptor antagonist

• With short half-life

• Popularly used in small animals esp. dogs for the relief of nausea & vomiting associated with chemotherapy, parvoviral enteritis, and gastric motility disorders

• Side effects in horse , dogs and cats: constipation

• Action may be antagonized by atropine and opioids

Maropitant citrate

• NK-1 receptor antagonist that blocks receptors found in the emetic center, CRTZ and in peripheral afferent nerves

• For dogs and cats (extralabel in cats)

• Adverse side effects: diarrhea, bloody stool, endoctoxic shock, otitis

Drugs that treat or prevent ulceration

1. antacids

2. H2 receptor antagonists

3. Proton pump inhibitors

4. synthetic prostaglandins

5. gastromucosal protectants

Gastric Ulcers

occurs in small & large animals in association with

• physiologic stress

• dietary management

• increased HCl production

• Drug therapy

Symptoms: anorexia, hematemesis, pain and melena

Antacids

Indications

• Gastric hyperacidity

• Peptic ulcers, gastric ulcers, gastritis, esophagitis, 

• Hyperphosphatemia in small animals (since antacids chelate intestinal phosphorus)

• Grain engorgement in ruminants (rumen acidosis)

MOA: Reduce HCl levels in the stomach

locally acting

Bases of Al, Mg, or Ca

• Neutralize stomach acid 

• ↓ pepsin activity

*Interfere with GI absorption of concurrently administered weak acid drugs