AHS 3307 Gastrointestinal Pharmacology Study Guide

What is peristalsis?

Wavelike contractions that propel gut contents aborally (away from the mouth)

What is the GI tract primarily controlled by?

The autonomic nervous system.

Parasympathetic GI Stimulation

Increases intestinal motility/GI secretions, relaxes sphincter.

what does Sympathetic GI Stimulation do

Decreases intestinal motility/GI secretions and contracts sphincter

GI Disease Symptoms

-Ptyalism

-Vomiting- Productive vs. Non-productive, proximity to eating

-Diarrhea- Large bowel vs. small bowel

-Decreased appetite

-Pain

-Regurgitation- Differentiate from vomiting

-Posture and stretching

Large Bowel GI Disease Symptoms

- Normal-large increase in frequency

-Decreased volume

-Tenesmus present

-Hematochezia

-Mucus present

Small Bowel GI Disease Symptoms

-Weight loss present

-Normal-mild increase in frequency

-Volume increased

-No Tenesmus

-Melina

-No Mucus

Antisialogues Drugs

-Decrease saliva

-Atropine and Glycopyrrolate (anticholinergic-blocks SLUDDE)

Anticholinergics as Antidiarrheals

•Block PNS stimulus of GI tract

•Rarely used in small animal due to systemic effects

•Atropine

•N-butylscopolammonium bromide (Buscopan)- Equine colic

Motility reducer

Anti-diarrheal Drugs

Anti-diarrheal Opioids

Reduce peristalsis

Anti-diarrheal Opioid Example

Loperamide (Immodium)- Binds mu receptors in GI tract

Antimicrobial Anti-diarrheal Drugs

Are controversial as of recently.

Metronidazole

Anti-diarrheal antibiotic with intestinal cell anti-inflammatory effect.

Sulfasalazine

Antidiarrheal antibiotic with GI anti-inflammatory effect.

Fenbendazole

Anti-diarrheal antiparasitic used when diarrhea is due to Giardia or other microbe. May affect bacterial antimicrobial resistance by changing the biome.

What antibiotic anti-diarrheal is effective against anaerobic bacteria and protozoa, specifically Giardia?

Metronidazole.

What is a Protectant GI drug?

A drug that works by coating inflamed intestinal mucosa with a protective layer.

What is an Adsorbent GI drug?

A drug that works by binding bacteria and/or digestive enzymes and/or toxins to protect intestinal mucosa from their damaging effects.

GI Protectant Drugs

Treat ulcers, inflammation, and diarrhea.

Sucralfate

An upper GI mucosal protectant drug

Activated Charcoal

An absorbent drug that absorbs ingested toxins to prevent contact with GIT.

Kaolin/Pectin

An absorbent drug that treats diarrhea and toxins.

Bismuth Subsalicylate (Pepto-Bismol)

Bismuth portion is a protectant, anti-toxin, and anti-bacterial. Subsalicylate portion is an aspirin-like drug that cannot be used in cats.

Probiotics

Repopulate GI tract with healthy or non-pathogenic bacteria.

Constipation

A condition in which 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.

Laxative

Medicine that loosens the bowel contents and encourages evacuation of the stool without excessive straining.

Cathartics

Harsher laxatives that result in soft to watery stool and abdominal cramping.

Osmotic Laxatives

Hyperosmolar content to pull water into the colon.

Lactulose

Disaccharide, metabolized by GI bacteria hyperosmolar acids.

Osmotic Laxative Example

Lactulose.

Stimulant Laxatives

Increase peristalsis by chemical irritation of intestine sensory nerve endings.

Bisacodyl (Dulcolax)

a stimulant laxative used in dogs and cats.

Castor Oil

An example of a stimulant laxative used in horses.

Bulk-Forming Laxatives

Fiber or synthetics that absorb water into intestines and increase fecal size.

Psyllium

An example of a bulk-forming laxative used in horses.

Sweet potato, canned pumpkin, veggies, bran.

Examples of bulk-forming laxatives.

Emollient Laxatives

Increase water retention in colon and/or lubricate feces by enhancing lipid absorption.

Docusate sodium (Pet-Ema, Docu-Soft)

An example of an emollient laxative.

Petroleum

an emollient laxative

Vomiting (Emesis)

The expulsion of stomach (sometimes duodenal) contents through the mouth.

Where is the vomiting center located?

In the Medulla Oblongata.

How can vomiting be initiated?

Through direct stimulation of the vomiting center, CRTZ (chemoreceptor trigger zone), or abdominal afferent nerves.

Anti-Emetic Drugs

Treat symptoms of vomiting.

Phenothiazines

Inhibit dopamine and muscarinic CRTZ receptors.

Acepromazine

An example of a phenothiazine.

Antihistamines

Block histamine receptor input into CRTZ.

Diphenhydramine

an antihistamine drug

Meclizine

An example of an antihistamine drug, used to treat vestibular disease.

Metoclopramide

Is a central CRTZ dopamine receptor antagonist drug, and Increases GI motility possibly by positively affecting acetylcholine receptors.

Serotonin Receptor Antagonists (Serotonin = 5HT3)

Stimulates 5-HT3 serotonin receptors located in CRTZ and peripherally in vagus nerve.

Ondanestron

a serotonin receptor antagonist drug

Maropitant (Cerenia)

Neurokinin-1 receptor antagonist in the vomiting center. Can also reduce MAC and visceral pain.

Do not give antiemetics unless GI obstruction has been ruled-out or is unlikely.

True.

Emetic Drugs

Drugs that induce vomiting.

Apomorphine

An emetic central-acting- CRTZ dopamine agonist drug.

3% Hydrogen Peroxide

An emetic, not recommended in cats, it stimulates gastric irritation nerves.

Xylazine/Dexmedetomidine

An emetic drug used to induce feline vomiting.

Ulcers

Erosions of mucosa, they are named according to the site of involvement.

Why do ulcers develop?

increased HCl production. Histamine, gastric, and acetylcholine influence acid production.

Antacid Drugs

Drugs that promote ulcer healing by neutralizing HCl and reducing pepsin activity.

Aluminum Hydroxide

An example of an antacid drug.

Histamine-2 (H2) Receptor Antagonists

Drug that inhibits acid production that competitively blocks the H2 receptors of the parietal cells in the stomach.

Ranitidine

An example of a Histamine-2 (H2) Receptor Antagonist.

Famotidine

a Histamine-2 (H2) Receptor Antagonists

Sucralfate

Anti-ulcer drug that is a mucosal protector in the stomach.

Misoprostal

Prostaglandin analog anti-ulcer drug, suppressing gastric acid production and increasing mucus production.

Proton Pump Inhibitors (PPI)

Bind irreversibly to the H+-K+-ATPase enzyme (proton pump) on the surface of the parietal cells of the stomach.

Omeprazole

An example of a PPI.

Prokinetic Agents

Increase the motility of parts of the GI tract to enhance movement of material through it.

Parasympathomimetic Agents

Increase intestinal motility and GI secretions and relax sphincters by stimulation of the parasympathetic nervous system.

what does Dopaminergic Antagonists do

Stimulate gastroesophageal sphincter tone, stomach motility, and intestinal motility by sensitizing tissues to the action of acetylcholine.

Cisapride

A 5-HT (Serotonin) Agonist, GIT serotonin receptors promote GI motility and other GI functions.

Pancrealipase

An enzyme supplement that not only contains primarily lipase (enzyme that digests fat) but also amylase (enzyme that digests starch) and protease (enzyme that digests proteins) to help with digestion.

Capromorelin (Entyce, Elura)

An FDA approved ghrelin receptor agonist that, when stimulated, growth hormone and cortisol release, and a sensation of hunger results. Mostly located in the brain.

Mirtazapine

Tetracyclic antidepressant that antagonizes Alpha-2, Serotonin, and Histamine Receptors

•Increased levels Norepinephrine that may stimulate appetite.

Cyproheptadine

Promotes appetite stimulation by antagonizing histamine and inhibiting serotonin receptors.

Benzodiazepines

Increases appetite by induction of GABA and by central inhibition of the satiety center in the hypothalamus.

Glucocorticoids-steroids

Stimulates steroid induced euphoria, which in turn stimulates appetite.

Propofol

Found to stimulate appetite in dogs when administered at sub-hypnotic.