PHARMACOLOGY - Gastrointestinal Pharmacology

Question 1

What are the two main areas in the brain which control vomiting?

Answer 1

Chemoreceptor trigger zone and vomiting centre

Question 2

What is the receptor located within the ‘vomiting centre’ of the central nervous system essential for inducing emesis?

Answer 2

Neurokinin-1 receptor (NK-1)

Question 3

What are the two most common emetic drugs used in veterinary medicine?

Answer 3

Xylazine
Apomorphine

Question 4

What are the four main anti-emetic drug types used in veterinary medicine?

Answer 4

Phenothiazines
Metoclopramide
Neurokinin-1 (NK-1) Antagonists
5HT3 Antagonists

Question 5

What can Phenothiazine drugs be used for other than as antiemetics?

Answer 5

Phenothiazines can also be used as sedatives

Question 6

How do Phenothiazines act as broad spectrum antiemetics?

Answer 6

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

Question 7

How do Phenothiazines act as sedatives?

Answer 7

Phenothiazines are weak cholinergic (muscarinic 1 (M1) receptor) antagonists

Question 8

How should Phenothiazines be administered?

Answer 8

Oral administration

Question 9

What are some of the potential side affects of Phenothiazines?

Answer 9

Hypotension
Bradycardia
Sedation

Question 10

What can Metoclopramide drugs be used for other than as antiemetics?

Answer 10

Metoclopramides can also be prokinetics (speed up gastric motility)

Question 11

How do Metoclopramides act as antiemetics?

Answer 11

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

Question 12

How should Metoclopramides be administered?

Answer 12

Oral, subcutaneous, intra-muscular or slow intravenous administration

Question 13

What are some of the potential side effects of Metoclopramides?

Answer 13

Movement disorders
Fatigue

Question 14

How do Neurokinin-1 (NK-1) Antagonists act as broad spectrum antiemetics?

Answer 14

Neurokinin (NK-1) Antagonists are NK-1 receptor antagonists in the chemoreceptor trigger zone and thus inhibit nausea and vomiting

Question 15

How should Neurokinin (NK-1) Antagonists be administered?

Answer 15

Oral or subcutaneous administration

Question 16

What are some of the potential side effects of Neurokinin (NK-1) Antagonists?

Answer 16

Hypersalivisation
Diarrhoea

Question 17

Why are 5HT3 Antagonists only used when Metoclopramide is ineffective?

Answer 17

Because 5HT3 Antagonists are so expensive

Question 18

How do 5HT3 Antagonists act as antiemetics?

Answer 18

5HT3 Antagonists are antagonists of 5HT3 receptors which are essential for vomiting, thus inhibiting this action

Question 19

What are some of the potential side effects of 5HT3 Antagonists?

Answer 19

These drugs are well tolerated and have very few side effects

Question 20

What are the five main drug types used to prevent and/or treat gastric ulceration?

Answer 20

Antacids
H2 receptor antagonists
Proton pump inhibitors
Prostaglandin (PGE2) analogues
Sucralfate

Question 21

What are some drugs that can actually cause gastric ulceration?

Answer 21

Non-steroidal anti-inflammatory drugs (NSAIDS)
Steroids

Question 22

How do antacids regulate gastric secretion?

Answer 22

Antacids chemically neutralise gastric HCl and inhibit pepsin secretion

Question 23

What is a downside to using antacids to treat gastric ulcers?

Answer 23

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

Question 24

What can H2 receptor antagonists be used to treat other than gastric ulceration?

Answer 24

Gastritis
Oesophagitis

Question 25

How do H2 receptor antagonists regulate gastric secretion?

Answer 25

H2 receptor antagonists are competitive antagonists for the H2 receptors in parietal cells, inhibiting the production of gastric HCl

Question 26

What is the most commonly used Proton-pump inhibitor drug?

Answer 26

Omeprazole

Question 27

What can Proton-pump inhibitors be used to treat and prevent other than gastric ulcers?

Answer 27

Gastritis Oesophagitis

Question 28

Which drug classes can be used to treat gastric ulcers caused by non-steroidal anti-inflammatory drugs (NSAIDS)?

Answer 28

Proton-pump inhibitors Prostaglandin (PGE2) analogues

Question 29

How do Proton-pump inhibitors regulate gastric secretion?

Answer 29

Proton-pump inhibitors inhibit the action of H+/K+ ATPase pumps present on the membrane of parietal cells

Question 30

Why do Proton-pump inhibitors accumulate in parietal cells?

Answer 30

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

Question 31

How do Prostaglandin (PGE2) analogues regulate gastric secretion?

Answer 31

Prostaglandin (PGE2) analogues are more stable versions of prostaglandin and act as prostaglandin receptor agonists, inhibiting gastric secretion

Question 32

What are some of the potential side effects of Prostaglandin (PGE2) analogues?

Answer 32

Diarrhoea

Question 33

(T/F) Prostaglandin (PGE2) analogues can be used in breeding and pregnant animals

Answer 33

FALSE. Prostaglandin (PGE2) analogues can cause abortion so should not be used in breeding or pregnant animals

Question 34

What can Sucralfates be used to treat other than gastric ulcers?

Answer 34

Duodenal ulcers

Question 35

How do Sucralfates regulate gastric secretion?

Answer 35

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

Question 36

What are some of the potential side affects of Sucralfates?

Answer 36

With long term use, Sucralfates can cause constipation

Question 37

What are the four commonly used anti-diarrhoeal agents used in veterinary medicine?

Answer 37

- Anticholinergics - Opioids - Absorbents - Aminosalicylates

Question 38

Which drug is good to use to treat the gut spasms associated with colic?

Answer 38

Anticholinergics

Question 39

How do opioids work to treat acute diarrhoea?

Answer 39

Opioids inhibit acetylcholine release in the myenteric plexus

Question 40

How do absorbents work to treat acute diarrhoea?

Answer 40

Absorbents form a protective coating on the inflamed gut mucosa

Question 41

Which disease is Aminosalicylates most commonly used to treat?

Answer 41

Chronic irritable bowel syndrome (IBD)/chronic colitis

Question 42

How do Aminosalicylates work to manage Chronic irritable bowel syndrome (IBD)/chronic colitis?

Answer 42

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

Question 43

What can be used to stimulate gut action?

Answer 43

Laxatives and cathartics