Anaesthetics

Question 1

What are the three key types of anti-emetics?

Answer 1

5HT3 receptor antagonists (serotonin)
D2 receptor antagonists (dopamine)
H2 receptor antagonists (histamine)

Question 2

Give an example of an 5HT3 receptor antagonist

Answer 2

Ondansatron

Question 3

When should you avoid using ondansatron?

Answer 3

If patient has a prolonged QT interval or taking drugs that can cause it

Question 4

Give 2 examples of D2 receptor antagonists

Answer 4

Metoclopramide
Domperidone

Question 5

What type of anti-ametic are the following drugs of? (Each individually)
- cyclizine
- domperidone
- ondanstatron
- metoclopramide
- promethazine
- cinnazine

Answer 5

• cyclizine - H2 (histamine) receptor antagonist
• domperidone - D2 (dopamine) receptor antagonist
• ondanstatron - 5HT3 (serotonin) receptor antagonist
• metoclopramide - D2 receptor antagonist
• promethazine - H2 receptor antagonist
• cinnazine - H2 receptor antagonist

Question 6

Mechanism of D2 receptor antagonists?

Answer 6

Prokinetic- relaxes pylorus, increases gut peristalsis, reduces oesophageal sphincter tone

Question 7

Side effects of D2 receptor antagonists?

Answer 7

Diarrhoea

Metoclopramide- Extrapyramidal SEs e.g. Acute dystonia, more common in young women
(Domperidone doesn’t cross blood brain barrier so doesn’t have same effect)

Question 8

When are D2 receptor antagonists useful?

Answer 8

With reduced gut motility e.g. with opioids

Question 9

Contraindications of D2 receptor antagonists?

Answer 9

Bowel obstruction
Bowel perforation

Question 10

Where do H2 receptor antagonists act?

When are they useful?

Answer 10

Vestibular system
Vomiting centre

Useful in
Motion sickness
Vertigo

Question 11

Side effects of H1 receptor antagonists?

Answer 11

Drowsiness
Blurred vision
Dry tongue
(Anti-cholinergic effect)
Can have transient tachycardia after IV

Question 12

Contraindications of H2 receptor antagonists?

Answer 12

BPH- can precipitate urinary retention