10.2.2 D2 and NK-1 antagonists Flashcards
What drugs can cause emesis?
COCAINE
Chemotherapy
Opioids
Cardiac- Digoxin
Anaesthetics
Illness- Antibiotics
NSAIDs
Enuresis- Diuretics cause this
What metabolites can cause emesis?
Uraemia
DKA
Addison’s disease
Hyperthyroidism
What toxins can cause emesis?
Bacteria
Toxins
What receptors are present in the CTZ?
D2
NK1
5HT3
What D2 antagonists are anti-emetics?
Metoclopramide
Domperidone
How does metoclopramide work?
Central dopamine antagonist
Peripheral cholinergic agonist
What cholinergic effects does metoclopramide have?
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
What are some adverse effects of metoclopramide?
Depression
Diarrhoea
Drowsiness
Hypotension
Galactorrhoea
Dystonia
Parkinsonism
When should metoclopramide not be given?
Post- GI surgery
GI obstruction
GI perforation
GI haemorrhage
How does domperidone work?
Central dopamine antagonist
Peripheral cholinergic agonist
Why is metoclopramide used over domperidone?
Increased risk of significant cardiac side effects
What can domperidone be used for?
Improving lactation in breastfeeding mothers
What are the adverse effects of domperidone?
Dry mouth
Long QT and VT
Galactorrhoea
Loss of libido
When should you not give domperidone?
Patients over 60 with arrhythmias
What anti-psychotics also act on D2 receptors in the CTZ?
Haloperidol
Drugs with the suffix -zine
How does haloperidol work?
D2 antagonists acting on the CTZ
What are the adverse effects of haloperidol?
Parkinsonism
Movement disorder
Long QT
Arrhythmia
Constipation
Dry mouth
When should haloperidol not be given?
Parkinson’s disease
CVD
Diabetes
Myasthenia gravis
How do drugs with -zine work?
D2 antagonists in the CTZ
What can drugs with -zine also block?
H1 and muscarinic receptors
Give some examples of -zine drugs
Prochloperazine
Chlorpromazine
Levomepromazine
What are the adverse effects of -zine drugs?
Drowsiness
Dry mouth
Movement disorder
Parkinsonism
Long QT
Urinary retention
How do NK1 antagonists work?
Prevents action of substance P at CTZ and in peripheral nerves
What are some other properties of NK1 antagonists?
- Boosts effects of serotonin antagonists
- Anxiolytic and antidepressant
- Good for chemotherapy- particularly for delayed emesis
Give 3 examples of NK1 antagonists
Aprepitant
Fosaprepitant
Netupitant
-pitant suffix
What are the adverse effects of NK1 antagonists?
Constipation
Headache
Asthenia
When should you not give NK1 antagonists?
Acute porphyrias
