Gastrointestinal Drugs

Question 1

What are the classes of antiemetic drugs?

Answer 1

NK1 antagonists
Metoclopramide
Phenothiazines
Antihistamines
5HT3 antagonists
Anticholinergics

Question 2

How does maropitant work?

Answer 2

Selective antagonist of Substance P at the NK1 receptor and inhibits the final common pathway involved in the vomiting reflex.

Question 3

When would you not use maropitant?

Answer 3

When GI obstruction is suspected

Question 4

How does metoclopramide work?

Answer 4

It antagonises D2 and 5HT3 receptors and has peripheral pro-cholinergic effects

Question 5

When is metoclopramide indicated?

Answer 5

Various emesis-inducing disorders
Cancer chemotherapy
Gastroesophageal reflux
Decreased gastric emptying e.g. ulcers, neoplasia, hypokalaemia, post-op GVD

Question 6

How do phenothiazines work?

Answer 6

Alpha 1 and 2 antagonist
D2 antagonist
H1 and H2 antagonist
Muscarinic cholinergic

Question 7

When are phenothiazines indicated in gastro cases?

Answer 7

Central or peripheral causes of vomiting but not veterinary registered so few indications in the UK.

Question 8

Why would you use antihistamines in a gastro case?

Answer 8

Histamine receptors in the CRTZ are involved in motion sickness in the dog but NOT cat

Question 9

What is the dose rate of maropitant?

Answer 9

1mg/kg SC or 2mg/kg PO SID for dogs

Question 10

What might be a contraindication in using metoclopramide?

Answer 10

Gastric obstruction
Epileptic patients (may increase frequency)

Question 11

Give examples of 5HT3 antagonists…

Answer 11

Dolasetron, ondansetron

Question 12

What are the clinical indications for 5HT3 antagonists in the gastro patient?

Answer 12

Extremely potent antiemetics. Can be used in cisplatin-induced emesis. They have sucessfully been used to control vomiting in the puppies with parvovirus

Question 13

Give examples of anti-ulcer drugs…

Answer 13

Nonsytemic antacides
H2 receptor anatagonists
Sucralfate
Misoprostol
Omeprazole

Question 14

Give examples of H2 receptor antagonists….

Answer 14

Cimetidine
Ranitidine
Famotidine

Question 15

How does omeprazole work?

Answer 15

Proton pump inhibitor

Question 16

When would you use a H2 receptor antagonist?

Answer 16

Effective in treating gastric ulceration caused by a variety of disorders including NSAIDs and uraemia

Question 17

When is sucralfate indicated in the gastric patient?

Answer 17

Symptomatic treatment of gastric ulceration

Question 18

When would you use misoprostol in the gastric patient?

Answer 18

Management of prevention of NSAID toxicity

Question 19

When would you use a motility modifying drug?

Answer 19

Rabbits - decreased GI motility

Cats - Megacolon

Question 20

What motility enhancing drugs are available?

Answer 20

Cisapride
- Upper and lower GI
Ranitidine
-Upper and some lower GI
Metoclopramide
- Some upper GI

Question 21

How do opioids affect the gut?

Answer 21

They increase segmental contractions in the gut and thus prolong transit time

Question 22

How do anticholinergics affect the gut?

Answer 22

They decrease peristalsis

Question 23

When might you use an anticholinergic for gut issues?

Answer 23

Management of spasmodic colic in the horse

Question 24

What drug would you use to induce emesis in the cat and dog?

Answer 24

Dog: apomorphine, a D2 agonist which is present in the CRTZ in the dog

Cat: Xyalzine as A2 receptors are more important in the cat

Question 25

What is mirtazapine and when is it used? At what dose?

Answer 25

A human antidepressant that is used in cats to stimulate appetite. Dose: 1.88mg/cat