Chapter 11 Gastrointestinal Drugs

Dr. Dipa Brahmbhatt VMD MpHDr. Dipa Brahmbhatt VMD MpHdbrahmbhatt@vettechinstitute.edudbrahmbhatt@vettechinstitute.edu

Emetics

• Emetics (don’t use in unconcious/seizuring/compromised animal)

– Drugs that induce vomiting

– Used in the treatment of poisoning and drug overdose

– Vomiting should not be induced if caustic substances have been ingested (Ammonia, lye, bleach)• Always check with poison control prior to inducing vomiting

– Can be centrally acting (working on the CRTZ) or peripherally acting (working on receptors locally)

Emetics

Centrally acting• Apomorphine (Apokyn)

– Choice for Dogs– Stimulates dopamine receptors in CRTZ– Morphine derived emetic– Peripherally: SQ/IM: vomit in 5-10 minutes– Subconjunctivally: Conjunctiva sac: vomit in 10 – 20 minutes– SE: Protracted vomiting, CNS depression and restlessness

• Xylazine– Choice for cats– SE: bradycardia, decreased respiratory rate

Inducing Emesis

Apomorphine

Xylazine

Emetics

Peripherally acting• Ipecac syrup

– 2 alkaloids: emetine & cephaelineIrritate gastric mucosa and stimulateCRTZ– Stomach and SI evacuated: 10-30 mins– SE: Higher doses cause CV problems

• Home remedies– Hydrogen peroxide– Salt and water/ mustard and water/ salt followed by water– Less reliable than other emetics

Emetics

• Activated charcoal is given if emesis is contraindicated

• It absorbs many chemicals and drugs in the upper GI tract

• Liquid/ Powder form (reconstituted with water)

• SE: Constipation, diarrhea and blackening of feces

• Superchan, Vet Powder, Vet Liquid, Toxiban (activated charcoal and kaolin)

Ulcers

• Ulcer: erosions of mucosa– Causes: metabolic disease, drug therapy & stress

– C.S.: Anorexia, melena, abdominal pain, and hematemesis

– Protected by • Mucus which protects mucosa from gastric secretions

• Sphincter muscles: cardiac and pyloric prevent reflux of acid to esophagus and duodenum

↑ release of HCL from parietal cells - stomach

Activated byHistamineGastrinAcetylcholine

AntacidSystemic: sodium bicarbonate, calcium carbonateNonsystemic: magnesium hydroxide, aluminum/magnesium hydroxide, aluminum hydroxide

Cimetidine (Tagament®)Ranitidine (Zantac®)Famotidine (Pepcid®)

Sucralfate

Misoprostol

OmeprazoleLansoprazole

Antiulcer Drugs

• Antiulcer drugs– Help prevent the formation of ulcers

– Categories include• Antacids

• Histamine-2 receptor antagonists

• Mucosal protective drugs

• Prostaglandin analogs

• Proton pump inhibitors

Antiulcer Drugs

• Antacids• Promote ulcer healing by neutralizing

HCl and reducing pepsin activity• Rapid onset and short duration of action• Interact with other drugs–By adsorption or binding the other drugs–By increasing stomach pH (decrease of absorption

of certain drugs)–By increasing urinary pH (inhibit elimination of

weak bases)

Antiulcer Drugs

• Antacids• May be systemic or nonsystemic• Examples:

– Systemic (in blood): sodium bicarbonate, calcium carbonate

– Nonsystemic (in GI): » Magnesium hydroxide: milk of magnesia, given to

cows to treat rumen acidosis (increases rumen pH)» Aluminum/magnesium hydroxide, aluminum

hydroxide: Mylanta used in foals and dogs in adjunct treatment for ulcer

» Aluminium hydroxide: Amphojel lowers phospahte levels

Antiulcer Drugs

• Histamine-2 receptor antagonists• Prevent acid reflux by competitively blocking the H2 receptors of

the parietal cells in the stomach, thus reducing gastric acid secretion

• SE: rare, diarrhea and inhibition of liver enzymes• Examples:

– Cimetidine (Tagament®)– Ranitidine (Zantac®)– Famotidine (Pepcid®)

Most potent Fewer SE than zantacLess bioavailable

More potent than tagamet Longer duration of actionThan tagamet

Antiulcer Drugs

Mucosal protective drugs Combine with protein to form an adherent

substance that covers the ulcer and protects it from stomach acid and pepsin

An example is sucralfate SE: Constipation Don’t give with H2 receptor antagonist

Mucosal protective drugs Combine with protein to form an adherent

substance that covers the ulcer and protects it from stomach acid and pepsin

An example is sucralfate SE: Constipation Don’t give with H2 receptor antagonist

Antiulcer Drugs

• Prostaglandin analogs• Suppress gastric secretions and increase mucus production in the

GI tract• An example is misoprostol, which is usually given to animals

taking NSAIDs• Pregnant women need to be careful while handling• SE: GI: diarrhea, vomiting, abdominal pain

• Proton pump inhibitors• Bind irreversibly to the H+-K+-ATPase enzyme on the surface of

parietal cells of the stomach; this inhibits hydrogen ion transport into the stomach so that it cannot secrete HCl

• Examples:– Omeprazole (gastroguard)– Lansoprazole

Antiulcer Drugs

• Omeprazole

– Horses and foals > 4 wks of age

– Heal gastric ulcer and prevent

re-occurrence

• Causes: feeding problems (less hay)

• Intensive training

• Development/growth

• Lansoprazole (Prevacid)

– Used to tx. Gastroesophageal reflux and ulcers

– Extra lable

BLOAT•Foamy/pasture/legume•Rumen is distended•Asphyxiate the animals

Antifoaming Agents

– Reduce or prevent the formation of foam

– Used in ruminants, whose rumens are subject to acute frothy bloat

– Make this foam less stable, breaking it up to promote gas release through belching

– Administered as solutions by stomach tube directly into the forestomach

– Examples include poloxalene and polymerized methyl silicone

Motility Enhancing

• Prokinetic agents– Increase the motility of parts of the GI tract to enhance

movement of material through it

– Types of prokinetic agents are:• parasympathomimetics• dopaminergic antagonists• serotonergic agents

Prokinetic Agents

• Parasympathomimetic agents include

– Acetylcholinesterase inhibitors, which compete with ACh for acetylcholinesterase, resulting in increased intestinal tone and salivation• An example is neostigmine• Tx of rumen atony and to diagnose

myasthenia gravis in dogs• SE: Vomiting diarrhea and increased

salivation

– Cholinergics, which make a precursor to acetylcholine• An example is dexpanthenol

Prokinetic Agents

• Dopaminergic agents stimulate gastroesophageal sphincter, stomach, and intestinal motility by sensitizing tissues to the action of the neurotransmitter ACh

• Examples include metoclopramide and domeridone• Don’t use reglan with antichlinergic drugs

• Serotonergic agents stimulate motility of the gastroesophageal sphincter, stomach, small intestine, and colon

• An example is cisapride

Enzyme Supplements

– Pancreatic enzymes must be supplemented in the diet when the pancreas is not functioning properly (as in pancreatic exocrine insufficiency)

– Pancrealipase contains primarily lipase, but also contains amylase and protease

– Can be irritating to the skin on contact and to nasal passages upon inhalation

Appetite-Stimulating Drugs

• Serotonin antagonist antihistamines– Promote appetite by inhibition at the serotoninergic receptors

which control satiety

– Side effects include sedation and dry mouth

• Benzodiazepines– Effective appetite stimulants in cats but not dogs

– Side effects include sedation and ataxia

• Tetracyclic antidepressants– Stimulate appetite by antagonizing alpha2-receptors

– Side effects include sedation, vocalization

Appetite Stimulating Drugs

• Glucocorticoids– Stimulate steroid-induced euphoria which stimulates

appetite

– Side effects include polydipsia, polyuria, dull haircoat, weight gain, and behavioral changes

• Anabolic steroids– Stimulate hematopoiesis, appetite, and weight gain

– Side effects include hepatotoxicity, masculinization, and early closure of growth plate in young animals

Appetite Stimulating Drugs

• Progestins– Used to stimulate appetite and promote weight gain in

anorectic cats and dogs

– Side effects include behavioral changes, endometritis, and mammary enlargement

Appetite Suppression

• Dirlotapide (Slentrol®)– Drug for management of obesity in dogs

– Side effects include vomiting, diarrhea, lethargy, and anorexia

Dental prophylaxis