Anti-Emetics Flashcards
Describe the pathophysiology of chemotherapy-induced nausea and vomiting (CINV)
Cisplatin is toxic to enterochromaffin cells (ECs) – release of free radicals
Free radicals – excessive 5-HT release
5-HT – activates 5-HT3A receptors
CTZ activates nerve fibres to the vomiting centre which causese nausea
Where are 5-HT3A receptors found
Nerve fibres to nucleus tractus solaris (NTS)
Nerves fibres to vomiting centre (VC)
Nerve fibres to chemoreceptor trigger zone (CTZ)
What is the treatment for chemotherapy-induced nausea and vomiting (CINV)
Ondansteron
Glucocorticoids
Arepepritant
What is ondansteron
5-HT3A receptor antagonist
Why are glucocorticoids used in chemotherapy-induced nausea and vomiting (CINV) treatment
Reduce free radical production
What is Arepepritant
neurokinin-1 receptor antagonist
Describe the pathophysiology of motion sickness
Neural mismatch activates histamine receptor on the vestibular nuclei
Vestibular nuclei activate muscarinic receptors on CTZ
CTZ activates VC which causes nausea
Vestibular system and hypothalamus may also activate the VC though cholinergic system
What is the treatment of motion sickness and how do they work
Promethazine - H1 receptor antagonist
Hyoscine (scopolomine) – non-selective muscarinic receptor antagonist
What is the pathophysiology of vomiting due to gastroparesis
Gastroparesis – delayed emptying of the stomach
- Reduced stomach contraction
- 5-HT – activates 5-HT3A receptors on the chemoreceptor trigger zone (CTZ)
- CTZ activates nerves fibres to vomiting centre (VC)
What is the treatment of nausea and vomiting
Metoclopramide
Why is metoclopramide used to treat nausea and vomiting
Dopamine D2 receptor antagonist Prokinetic – stimulates gastric emptying Inhibits D2 receptors in VC 5-HT3A receptor antagonist Inhibits activation of CTZ
What are the mechanistic triggers of nausea and committing
Cytotoxic drugs
Motion sickness
GI problems
Pregnancy
Summarise the physiological control of nausea and vomiting
Chemoreceptor trigger zone - multiple inputs
Vomiting centres - Muscarinic receptors
What are the classes of anti-emetic drugs
5-HT3A receptor antagonists
Histamine H1 receptor antagonists
Muscarinic receptor antagonists
Dopamine D2 receptor antagonists
Which receptors are found in the chemoreceptor trigger zone
5-HT3A receptor
muscarinic receptor
dopaminergic receptors
H1 receptors
