Anti-emetics Flashcards
What are some things that can cause nausea and vomiting and why?
Chemotherapy-irritable effect on stimach and enterochromaffin cells-release more of 5HT
Motion sickness-labyrnth mismatch of sight vs what its feeling-> activate histamine receptor on vestibular nuclei
Gatroporesis-delayed stomach empying
infection (GI)
pregnancy
cytotoxic drugs
Other higher function
What is the role of enterochromaffin cells in nausea?
In the stomach, when irritation and excess ROS from the EC-> cause release of excessive 5-HT
Activates 5-HT3a receptor on nerves fibres to the chemoreceptor trigger zone (in brain but out of BBB)
CTZ has fibers going to the Vomitting centre (muscarinin receptors)
VC-> when activated cause nausea
What is ondansteron?
5HT3a receptor antagonist–stops enterochromaffin fro singalling to the nerves
First line treatment for nausea (especially chemo ones)
usually given in triple therapy-with glucocorticoids and Aprepitant
is Ondansetron often given alone for chemotherapy nausea? Why?
No usually triple therapy
Ondansetron
Glucocorticosteroids (reduce ROS production
Aprepitant-neurokinin1 receptor angtagnost-inhbits subtance B
usually nausea is biphasic-immediate nausea, and then will come again
Ondansetron very good for earlier, the rest treat the later one better
What is the physiology of motion sickness induced nausea?
Motion sickness-labyrnth mismatch of sight vs what its feeling-> activate histamine receptor (H1) on vestibular nuclei
Vestibular nulcei activate muscarinic receptors on CTZ again
CTZ activates muscarinic on VC->nausea
(not one specific Muscarinic is believed to cause nausea)
what is a treatment for motion sickness nausea?
In very severe cases/long journeys
Promethazine-H1 receptor antagnists (in the vestibular nuclei)
Hyoscine (scopolomine)-non selective muscarinic receptor antagnost that works in CNS
How does gastroparesis can cause nausea? What is the role of the dopamine D2 receptor>
gastroparesis-delayed emptying of stomach
Also cause release of 5HT–activate the CTZ center -> muscarininc receptor of VC
D2 is located on the CTZ and when very active (like from LevoDopa)-cause vomiting D2 activation (When highly active) can cause nausea and vomiting
What a is metoclopramide?
Dual funtion of D2 receptor antagonise AND 5HT3a receptor antagonist
very effective especially in gastroparesis, but can be useful in other
Side effects of antiemetics
5HT antagonists-headache constipation
Musc antagonist-musc side effecys
Dopamine-extrapyrimidal effects, galactohrroea
Histamine-Drowsiness
