GI Drugs Flashcards
T/F: Emetic drug apomorphine is typically used in cats, while xylazine is used to induce vomiting in dogs.
F
It is the opposite.
T/F: Antacids work by decreasing the gastric pH and increasing the hydrochloric acid secretion in the stomach.
F
Antacids increase the gastric pH (making it more basic) which decrease the HCl in the stomach.
T/F: Dexmedetomidine is the best emetic for cats, while apomorphine is the best emetic for dogs.
T
Dexmedetomidine and xylazine are used to induce vomiting in cats. Apomorphine is used in dogs.
T/F: GI drugs like laxatives can cause constipation or be used to ensure there are contents in the lower intestinal tract prior to medical procedures.
F
Laxatives treat constipation or clear the lower intestinal tract of its contents.
T/F: Antiemetic drugs are appetite stimulants
F
Antiemetics are anti-nausea drugs that prevent nausea and vomiting. Appetite stimulants on the other hand promote eating.
What does the parasympathetic NS do to GI motility, GI secretions, blood flow to GI tract, and the digestion and absorption of food? Why?
Increases b/c it is the rest and restore system.
What does the What does the sympathetic NS do to GI motility, GI secretions, blood flow to GI tract, and the digestion and absorption of food? Why? NS do to the
Reduce because it is the fight of flight system, and those things are not necessary if you’re in flight mode and might die.
What are the 6 receptors on the emetic center?
Acetycholine NE/Epinephrine Histamine Serotonin (5-HT) Substance P (NK1-receptor)
5 mechanisms that produce vomiting
- Direct stimulation of the emetic center receptors
- Drugs of chemicals in blood or CSF that stimulate the Chemoreceptor Trigger Zone
- Distention/irritation of pharynx, GI tract, kidney, gall bladder, peritoneum, uterus
- Stimulation of the balance center of the inner ear
- Higher centers/motional centers of the brain send signals to the emetic center
4 animas where you should NEVER induce emesis
horses
rabbits
rats
guinea pigs
What are peristaltic contractions? What do they do?
- move food along GI tract in waves
- relaxes bowel in front of food bolus then constricts behind food bolus to push the bolus forward
- increased peristalsis increases speed at which ingesta moves along the GI tract, meaning food is unable to be digested well
What are segmental contractions?
- caused by circular contractions of a segment of bowel
- mixes contents of bowel to expose more food to digestive enzymes
- slows the movement of ingesta along the length of the bowel
What cells produce acid in the stomach?
Parietal cells
What are the 3 receptors found on parietal cells that, when stimulated, produce acid?
- H2 Receptor (Histamine molecule)
- Acetylcholine Receptor (acetylcholine molecule)
- Gastrin Receptor (gastrin molecule)
What does bicarbonate do?
it helps to neutralize the acid; can be found in mucus
What are the 2 centrally acting emetic drugs?
Apomorphine
Xylazine
What receptors does apomorphine stimulate?
dopamine
What receptor does xylazine stimulate?
alpha receptors
What is a locally acting emetic? Name it and how it works.
It irritates the GI tract itself, distending the stomach and sending PNS signals (acetylcholine) via the vagus nerve to the emetic center.
Hydrogen Peroxide (must be fresh with fizz, may produce gastritis)
Why is acepromazine used as an antiemetic drug?
It blocks dopamine, alpha, and histamine receptors which are all receptors that, if stimulated, could cause emesis.
What is a side effect seen with acepromazine and why? What patients should you not give Ace to because of it?
- it blocks alpha-1 receptors which are responsible for vasoconstriction
- DO NOT use in dehydrated patients who may have a lower blood volume and thus decreased arterial blood pressure already
if vasoconstriction is blocked from happening, the body won’t be able to increase its blood pressure.
Name the 2 antihistamines that can be used as antiemetics. Why?
Diphenhydramine & dimenhydrinate
Both block histamine receptors
What are 2 prokinetic drugs that can be antiemetic?
Metoclopramide
Cisapride
How does metoclopramide work?
blocks dopamine receptors centrally
Locally it…
- increases motion in the correct direction
- prevents stomach from stopping
- increases muscle tone of lower esophagus making it harder for things to reflux back up
What is the serotonin receptor blocker used as an antiemetic?
Ondansetron
What is the active drug name for Cerenia? What does it block?
maropitant
blocks NK-1 receptors
Name 2 opioid antidiarrheal drugs
Loperamide
Diphenoxylate
What do loperamide and diphenoxylate do to decrease diarrhea?
stimulate mu receptors which…
- increases segmental contractions
- mildly decreases peristalsis
- decreases secretions
What is the general principle for how laxatives, cathartics, and purgatives work?
increase fluid content of feces by making them softer
What does a bulk laxative do?
adds fiber to the diet creating an osmotic force that retains water
How does an irritant laxative work?
It irritates the bowel which increases peristalsis and agressive movement
Name an irritant laxative
bisacodyl
Do not use ____________ laxatives or enemas in cats or small dogs
phosphorus
Name a hyperosmotic drug
Lactulose
Name non-systemic antacids
Tums
Rolaids
Mylanta
What to non-systemic antacids do?
directly neutralize the acid by combining with it and turning it into a less acidic molecule
What can antacids interfere with and why?
Absorption of drugs from the stomach b/c they cause more alkaline pH in stomach, so more acidic drugs may become more ionized and not be able to absorbed as well across the membrane
chelation may also cause drug to precipitate out of solution and not be absorbed
How can you recognize systemic antacids that are receptor inhibitors?
-tidine suffix
How do systemic antacids work? (2 ways)
- Attach to and block stimulatory effect on parietal cell receptors (H2, AcH, Gastrin)
- attach to the proton pump and prevent it from pumping H+ ions into the stomach lumen regardless of how much the parietal cell is being stimulated
Cimetidine, ranitidine, famotidine, and nizatidine are all what type of drug?
Systemic antacids (receptor inhibitors)
Name 2 systemic antacids that are proton pump inhibitors
omeprazole
esomeprazole
Name one synthetic prostaglandin
Misoprostol
What does misoprostol do?
increases mucus production
decreased acid production
increases rate of cell turnover so ulcers/injuries heal faster
What is the downside to using misorpostol?
it affects almost every place in the body that uses prostaglandins, so there can be a long list of side effects
What drug is the “Gastric band-aid” and why is it called that?
Sucralfate
- when it is exposed to acid, it forms a sticky paste that binds to the ulcer site, providing a physical barrier between the ulcer and the stomach acid
- stimulates local production of PGs which helps protect and heal the ulcer
What drug should not be combined with sucralfate and why?
antacids because sucralfate needs an ACIDIC environment to work, and antacids remove that acidity
