10.2.2 D2 and NK-1 antagonists

Question 1

What drugs can cause emesis?

Answer 1

COCAINE

Chemotherapy
Opioids
Cardiac- Digoxin
Anaesthetics
Illness- Antibiotics
NSAIDs
Enuresis- Diuretics cause this

Question 2

What metabolites can cause emesis?

Answer 2

Uraemia
DKA
Addison’s disease
Hyperthyroidism

Question 3

What toxins can cause emesis?

Answer 3

Bacteria
Toxins

Question 4

What receptors are present in the CTZ?

Answer 4

D2
NK1
5HT3

Question 5

What D2 antagonists are anti-emetics?

Answer 5

Metoclopramide
Domperidone

Question 6

How does metoclopramide work?

Answer 6

Central dopamine antagonist
Peripheral cholinergic agonist

Question 7

What cholinergic effects does metoclopramide have?

Answer 7

Increases ACh at muscarinic receptors in gut
Promotes gastric emptying:
- Increased tone at LOS- makes it close
- Increased tone and amplitude of gastric contractions
- Decreased tone of pylorus- makes it open
- Increased peristalsis

Question 8

What are some adverse effects of metoclopramide?

Answer 8

Depression
Diarrhoea
Drowsiness
Hypotension
Galactorrhoea
Dystonia
Parkinsonism

Question 9

When should metoclopramide not be given?

Answer 9

Post- GI surgery
GI obstruction
GI perforation
GI haemorrhage

Question 10

How does domperidone work?

Answer 10

Central dopamine antagonist
Peripheral cholinergic agonist

Question 11

Why is metoclopramide used over domperidone?

Answer 11

Increased risk of significant cardiac side effects

Question 12

What can domperidone be used for?

Answer 12

Improving lactation in breastfeeding mothers

Question 13

What are the adverse effects of domperidone?

Answer 13

Dry mouth
Long QT and VT
Galactorrhoea
Loss of libido

Question 14

When should you not give domperidone?

Answer 14

Patients over 60 with arrhythmias

Question 15

What anti-psychotics also act on D2 receptors in the CTZ?

Answer 15

Haloperidol
Drugs with the suffix -zine

Question 16

How does haloperidol work?

Answer 16

D2 antagonists acting on the CTZ

Question 17

What are the adverse effects of haloperidol?

Answer 17

Parkinsonism
Movement disorder
Long QT
Arrhythmia
Constipation
Dry mouth

Question 18

When should haloperidol not be given?

Answer 18

Parkinson’s disease
CVD
Diabetes
Myasthenia gravis

Question 19

How do drugs with -zine work?

Answer 19

D2 antagonists in the CTZ

Question 20

What can drugs with -zine also block?

Answer 20

H1 and muscarinic receptors

Question 21

Give some examples of -zine drugs

Answer 21

Prochloperazine
Chlorpromazine
Levomepromazine

Question 22

What are the adverse effects of -zine drugs?

Answer 22

Drowsiness
Dry mouth
Movement disorder
Parkinsonism
Long QT
Urinary retention

Question 23

How do NK1 antagonists work?

Answer 23

Prevents action of substance P at CTZ and in peripheral nerves

Question 24

What are some other properties of NK1 antagonists?

Answer 24

• Boosts effects of serotonin antagonists
• Anxiolytic and antidepressant
• Good for chemotherapy- particularly for delayed emesis

Question 25

Give 3 examples of NK1 antagonists

Answer 25

Aprepitant
Fosaprepitant
Netupitant

-pitant suffix

Question 26

What are the adverse effects of NK1 antagonists?

Answer 26

Constipation
Headache
Asthenia

Question 27

When should you not give NK1 antagonists?

Answer 27

Acute porphyrias