PHARMACOLOGY - Gastrointestinal Pharmacology Flashcards
What are the two main areas in the brain which control vomiting?
Chemoreceptor trigger zone and vomiting centre
What is the receptor located within the ‘vomiting centre’ of the central nervous system essential for inducing emesis?
Neurokinin-1 receptor (NK-1)
What are the two most common emetic drugs used in veterinary medicine?
Xylazine
Apomorphine
What are the four main anti-emetic drug types used in veterinary medicine?
Phenothiazines
Metoclopramide
Neurokinin-1 (NK-1) Antagonists
5HT3 Antagonists
What can Phenothiazine drugs be used for other than as antiemetics?
Phenothiazines can also be used as sedatives
How do Phenothiazines act as broad spectrum antiemetics?
Phenothiazines act as D2 (dopamine receptor) antagonists in the chemoreceptor trigger zone. This prevents stimulation of these dopamine receptors and thus prevents nausea and vomiting
How do Phenothiazines act as sedatives?
Phenothiazines are weak cholinergic (muscarinic 1 (M1) receptor) antagonists
How should Phenothiazines be administered?
Oral administration
What are some of the potential side affects of Phenothiazines?
Hypotension
Bradycardia
Sedation
What can Metoclopramide drugs be used for other than as antiemetics?
Metoclopramides can also be prokinetics (speed up gastric motility)
How do Metoclopramides act as antiemetics?
Metoclopramides act as D2 (dopamine receptor) antagonists in the chemoreceptor trigger zone. This prevents stimulation of these dopamine receptors and thus prevents nausea and vomiting
How should Metoclopramides be administered?
Oral, subcutaneous, intra-muscular or slow intravenous administration
What are some of the potential side effects of Metoclopramides?
Movement disorders
Fatigue
How do Neurokinin-1 (NK-1) Antagonists act as broad spectrum antiemetics?
Neurokinin (NK-1) Antagonists are NK-1 receptor antagonists in the chemoreceptor trigger zone and thus inhibit nausea and vomiting
How should Neurokinin (NK-1) Antagonists be administered?
Oral or subcutaneous administration
What are some of the potential side effects of Neurokinin (NK-1) Antagonists?
Hypersalivisation
Diarrhoea
Why are 5HT3 Antagonists only used when Metoclopramide is ineffective?
Because 5HT3 Antagonists are so expensive
How do 5HT3 Antagonists act as antiemetics?
5HT3 Antagonists are antagonists of 5HT3 receptors which are essential for vomiting, thus inhibiting this action
What are some of the potential side effects of 5HT3 Antagonists?
These drugs are well tolerated and have very few side effects
What are the five main drug types used to prevent and/or treat gastric ulceration?
Antacids
H2 receptor antagonists
Proton pump inhibitors
Prostaglandin (PGE2) analogues
Sucralfate
What are some drugs that can actually cause gastric ulceration?
Non-steroidal anti-inflammatory drugs (NSAIDS)
Steroids
How do antacids regulate gastric secretion?
Antacids chemically neutralise gastric HCl and inhibit pepsin secretion
What is a downside to using antacids to treat gastric ulcers?
Antacids can cause rebound acid secretion where the neutralisation of the pH caused by the Antacids actually stimulates more acid production in the stomach which can lead to impaired absorption of other drugs
What can H2 receptor antagonists be used to treat other than gastric ulceration?
Gastritis
Oesophagitis
How do H2 receptor antagonists regulate gastric secretion?
H2 receptor antagonists are competitive antagonists for the H2 receptors in parietal cells, inhibiting the production of gastric HCl
What is the most commonly used Proton-pump inhibitor drug?
Omeprazole
What can Proton-pump inhibitors be used to treat and prevent other than gastric ulcers?
Gastritis
Oesophagitis
Which drug classes can be used to treat gastric ulcers caused by non-steroidal anti-inflammatory drugs (NSAIDS)?
Proton-pump inhibitors
Prostaglandin (PGE2) analogues
How do Proton-pump inhibitors regulate gastric secretion?
Proton-pump inhibitors inhibit the action of H+/K+ ATPase pumps present on the membrane of parietal cells
Why do Proton-pump inhibitors accumulate in parietal cells?
Proton-pump inhibitors are weak bases. This weak base enables Proton-pump inhibitors to accumulate in the acidic space of the secretory region of parietal cells
How do Prostaglandin (PGE2) analogues regulate gastric secretion?
Prostaglandin (PGE2) analogues are more stable versions of prostaglandin and act as prostaglandin receptor agonists, inhibiting gastric secretion
What are some of the potential side effects of Prostaglandin (PGE2) analogues?
Diarrhoea
(T/F) Prostaglandin (PGE2) analogues can be used in breeding and pregnant animals
FALSE. Prostaglandin (PGE2) analogues can cause abortion so should not be used in breeding or pregnant animals
What can Sucralfates be used to treat other than gastric ulcers?
Duodenal ulcers
How do Sucralfates regulate gastric secretion?
Sucralfates trigger a polymerisation reaction creating a viscous gel at a low pH, which binds to exposed proteins i.e. ulcerated tissue to allow the tissue to heal
What are some of the potential side affects of Sucralfates?
With long term use, Sucralfates can cause constipation
What are the four commonly used anti-diarrhoeal agents used in veterinary medicine?
- Anticholinergics
- Opioids
- Absorbents
- Aminosalicylates
Which drug is good to use to treat the gut spasms associated with colic?
Anticholinergics
How do opioids work to treat acute diarrhoea?
Opioids inhibit acetylcholine release in the myenteric plexus
How do absorbents work to treat acute diarrhoea?
Absorbents form a protective coating on the inflamed gut mucosa
Which disease is Aminosalicylates most commonly used to treat?
Chronic irritable bowel syndrome (IBD)/chronic colitis
How do Aminosalicylates work to manage Chronic irritable bowel syndrome (IBD)/chronic colitis?
Aminosalicylates are cleaved into sulfapyridine and 5-aminosalicylic acid by bacteria in the colon. 5-aminosalicylic acids have anti-inflammatory effects which can be used to manage these chronic diseases
What can be used to stimulate gut action?
Laxatives and cathartics
