Anti-Emetics Flashcards
A man presents with:
• Chemotherapy (Cisplatin) for lung cancer
• Chemotherapy induced nausea & vomiting (CINV)
Explain the pathophysiology
Cisplatin is TOXIC to enterochromaffin cells (ECs)
• releases free radicals = excessive 5-HT release
5-HT activates 5-HT3a receptors on nerve fibres to chemoreceptor trigger zone (CTZ)
• CTZ activates nerve fibres to vomiting centre = nausea
A man presents with:
• Chemotherapy (Cisplatin) for lung cancer
• Chemotherapy induced nausea & vomiting (CINV)
Explain the Treatment options
Ondansetron:
• 5-HT3a receptor antagonist
Glucocorticoids:
• reduce free radical production
Aprepitant:
• neurokinin-1 receptor antagonist
A man presents with:
• Motion sickness
Explain the pathophysiology
Labyrinth - neural mismatch
• activates histamine receptors on vestibular nuclei
Vestibular nuclei activate muscrainic receptors on CTZ
• CTZ activates VC = nausea
A man presents with:
• Motion sickness
Explain the Treatment options
Promethazine:
• H1 receptor antagonist
Hyoscine (scopolomine):
• non-selective muscrainic receptor antagonist
A woman presents with:
• Vomiting due to unknown cause
• Abdominal pain & bloating
• History of type 2 diabetes
Explain the pathophysiology
Gastroparesis
• delayed emptying of the stomach
Reduced stomach contaction
5-HT activates 5-HT3a receptors on CTZ
• CTZ activates nerve fibres to VC = nausea
A woman presents with:
• Vomiting due to unknown cause
• Abdominal pain & bloating
• History of type 2 diabetes
Explain the Treatment options
Metoclopramide:
• D2 receptor antagonist
- Prokinetic - stimulates gastric emptying
- Inhibits D2 receptors in CTZ
• 5-HT3a receptor antagonist
- inhibits activation of CTZ
What are the physiological control of nausea/vomiting?
Chemoreceptor Trigger Zone (CTZ):
• receives multiple inputs from areas including stomach & vestibular nuclei
CTZ communicates with the VC = nausea & vomiting
What are the main mechanistic triggers of nausea/vomiting?
- Cytotoxic drugs
- Motion sickness
- GI problems
- Pregnancy
- Other higher functions
What are the main classes of anti-emetic drugs?
(1) 5-HT3a receptor antagonists
(2) Histamine H1 receptor antagonists
(3) Muscarinic receptor antagonists
(4) Dopamine D2 receptor antagonists
Outline the principle clinical uses and MoA of the classes of anti-emetic drugs
(1) 5-HT3a receptor antagonists
• chemotherapy induced N&V
(2) Histamine H1 receptor antagonists
• motion sickness
(3) Muscarinic receptor antagonists
• motion sickness
(4) Dopamine D2 receptor antagonists
• gastroparesis induced N&V
What side-effects would you expect from centrally acting muscarinic receptor antagonists?
x Galactorrhoea x Drowsiness x Dry mouth x EPS x Headaches
Drowsiness
&
Dry mouth
What side-effects would you associate with histamine H1 receptor antagonism?
x Galactorrhoea x Drowsiness x Constipation x EPS x Headaches
Drowsiness
What side-effects would you associate with dopamine D2 receptor antagonism?
x Galactorrhoea x Drowsiness x Constipation x EPS x Headaches
Galactorrhoea
&
EPS
What side-effects would you associate with 5HT3A receptor antagonism?
x Galactorrhoea x Drowsiness x Conspitation x EPS x Headaches
Constipation
&
Headaches
