Pharmacology GI drugs

2 types of intestinal movements

Peristalsis and Segmentation

Peristalsis

Propels contents along digestive tract by waves of contractions.

Segmentation

Periodic repeating pattern that mixes and churns the contents of intestines

Why does vomiting occur

When emetic center in the medulla is activated after signals are sent from the CRTZ

what is the CRTZ

Chemoreceptor trigger zone

What animals should emetics not be given in

Rabbits, some rodents, horses

What % of stomach contents are removed when vomiting

80%

How do most emetics work

By stimulating the CRTZ

Apomorphine (emetic)

Morphine derivative (stimulated CRTZ), given topically, parenterally, or in the conjunctival sac. Not controlled or used in cats

Opthalmic emetic solution for dogs?

Ropinirole (Clevor)

Xylazine (emetic)

It is an alpha 2 Adrenergic agonist used for sedation and analgesia but causes vomiting when given in cats IM.

Emetics

Apomorphine, Ropinirole(clevor), Xylazine, Syrup of Ipecac, hydrogen peroxide

Syrup of Ipecac

Used in dogs and cats but not recommended for animals with heart conditions.

Hydrogen peroxide (emetic)

Dogs only. No more than 2 doses in 15 mins. Repeated doses is not recommended and high risk of inducing gastritis

What must be noted about Anti emetics

That they do not solve the underlying cause just address the vomiting.

Can antihistamines be used as anti emetics?

Yes they sedate and block vomiting level at CRTZ. Used for travel motion sickness

6 classes of antiemetic

Phenothiazines tranquilizers, Anticholinergics, Prokinetics, Antihistamines, Serotonin Agonist, and Neurokinin Antagonist (NK-1).

Phenothiazine tranquilizers (anti-Emetic)

Chlorpromazine (main), Acepromazine, prochlorperazine.

Antihistamines (antiemetics)

Dimenhydrinate (Dramamine), Diphenhydramine (Benadryl).

Anticholinergics (antiemetic)

Centrine (Aminopentamde), Scopolamine (antispasmodic, not recommended as much)

Prokinetics (Antiemetic)

Metoclopramide (Reglan), used with Parvo. Seizure contraindications.

Serotonin Antagonist

Ondansetron (Zofran), Granisetron (Kytril)

NK-1 Receptor Agonist

Maropitant (Cerenia)

Antacids what are they

Treat gastric ulcers.

H2 receptor blocker Antiulcer meds

Cimetidine, Ranitidine, Famotidine

Cimiditine

Used for stomach ulcers, espphagitis, gastric reflux, hypersecretory conditions

Ranitidine

Zantac. 5x more potent than Tagamet

Famotidie

Pepcid/ AC, works well being found in OTC version.

Proton Pump inhibitors (antulcer)

Omeprazole (Prilosec) and Esomeprazole (Nexium)

Local antacids

Maalox, magnalax, mylanta, Di-Gel, milk of magnesia, amphojel.

Gastromucosal protectants

Sucrafalfate and Misoprostol

Sucralfate

Carafate, only one used commonly in vet med. should be given 30 mins before giving antacids because needs acid environment for effectiveness

Misoprostol

Cytotec. Prostaglandin E to increase mucus secretion. Not useful in horses!

Misoprostol side effects

Diarrhea, vomiting, flatulence, and abdominal pain

Antidiarrheal meds

Opiates, secretion reducers, protectants and absorbents

Opiates as anti diarrheals

Decrease intestinal secretions, enhance absorption and increase segmental contractions. Lomotil and Imodium

What types of drugs were considered ineffective for treating diarrhea

Anticholinergics and Antispasmodics.

Secretion reducers (antidiarrheal)

Bismuth subsalicylate, Sulfasalazine (Azlfidine) sulfa antibiotic. These are not used in cats due to conversion of NSAIDs.

Side effect of secretion reducers

Dark stools resembling melena

Protectants/ Adsorbents

Serotonin agonist (Ondansetron (Zofran), activated charcoal

Activated Charcoal

Toxiban. Adsorbs effect from drugs and poisons accidentally ingested that have not been vomited or used in addition

Laxative

Substances that loosen bowel contents and encourage evacuation

Categories of laxatives

Lubricants/stool softeners, bulk producing, saline/hyperosmotic, irritants, misc.

Lubricants

Made of oils and softens stool. Mineral oil, petrolatum, (laxatone), cod liver oil.

Bulk producing agents

Most used in horses that have sand impactions. Metamucil, equine psyllium, bran mash.

Stool softners

Main ingredient is diocytl sodium sulfosuccinate (DSS). They reduce surface tension and allow water to penetrate GI contents

Saline/hyperosmotic agent

Lactulose. More of a cathartic. Magnesium hydroxide (milk of magnesium when suspended)

Irritants

Irritating gut wall, increasing stimulation of muscles and peristalsis. Not used much in vet med. Castor oil

GI stimulants

Stimulate GI motility. Metoclopramide (Reglan) is main choice, also an antiemetic. Cisapride (Propulsid)

Motilin like drugs

Erythromycin/ stimulates motility and can act like a prokinetic. Treats bacterial and mycoplasma infections

Misc GI drugs

metronidazole (Flagyl): treats Giardia and anaerobic infections. Tylosin: extra label to treat bacterial overgrowth. Is toxic in horses

Antibloat meds

Reduce “froth” in the rumen. Dioctyl sodium succinate (DSS), Poloxalene

Weight loss drugs

Dirlotapide (Selentrol), Voikase pancrezyme.

Appetite stimulants

Diazepam, alprazolam, cyproheptadine, Mirtazapine

Some reasons emesis should not be induced

If high risk of aspirating. If there is convulsing or pre-seizure (preictal) symptoms. If animal has ingested volatile petroleum liquids gas)

4 types of diarrhea

Secretory, educative, motility, osmotic, malabsorption.

Tenesmus

When inflammation or irritation stimulates reflex to defecate rather than fecal material and the animal ends up straining.

Side effect of Sulfasalazine that needs to be watched for

Vomiting, KCS.

What cells are responsible for acid secretion in the stomach

Chief cells

Non systemic antacids

Magnesium hydroxid, Tums, Rolaids.

What is a Ruminatoric

Prokinetic drug that stimulates an atonic flaccid rumen.

Ionophores

Antimicrobial drug used in livestock to control coccidia.

Side effect of metronidazole

CNS signs like weakness, head tilt, staggering, disorientation, proprioceptive deficits, and seizures.

Oral electrolytes are used for what?

Secretory diarrhea

Sulfasalazine is used to treat what GI condition

Inflammatory colitis

Pancreatic enzyme supplicments are for that

Exocrine pancreatic insufficiency

Lactulose is used in cats with what

Hepatic encephalopathy

Appetite stimulant only used for dogs?

Dirlotapide