Anti-Emetics Flashcards
State the 4 major classes of anti-emetic drugs.
5-HT3A receptor antagonists
Histamine H1 receptor antagonists
Muscarinic receptor antagonists
Dopamine (D2) receptor antagonists
What is special about the location of the CTZ and vomiting centre?
In a part of the brain that has a very porous BBB
So act as an early warning system to protect the brain from toxin damage
Describe the pathophysiology of chemotherapy induced nausea and vomiting
Drug is toxic to enterochromaffin cells in gastric antrum, stimulates excessive release of 5HT
5HT binds to 5HT 3A receptors on nerve fibres to chemoreceptor trigger zone
CTZ activates nerve fibres to the vomiting centre, inducing nausea + vomiting
What class of drug is primarily used for chemotherapy induced nausea and vomiting? Give an example
5HT 3A receptor antagonist
Ondansetron (as part of triple therapy with glucocorticoid + neurokinin 1 receptor antagonist)
Describe the pathophysiology of motion sickness
Neural mismatch in the labyrinth activates histamine receptors on vestibular nuclei
Vestibular nuclei activate muscarinic receptors on CTZ
CTZ activates VC, causing nausea
Name 2 classes of drugs indicated for treatment of motion sickness. Give examples of each.
H1 receptor antagonist e.g. Promethazine (inhibits H1 stimulation in vestibular nuclei)
Non-selective muscarinic receptor antagonists e.g. Hyoscine (inhibit muscarinic stimulation of CTZ + VC)
What is gastroparesis? What does this cause associated with nausea and vomiting?
Delayed emptying + lack of contraction of the stomach
Excessive release of 5HT, which activates 5HT 3A receptors on CTZ + stimulates activation of VC
Give an example of a drug used to treat nausea and vomiting associated to gastroparesis? Describe its mechanism of action.
Metoclopramide
D2 receptor antagonist (pro kinetic, stimulates gastric emptying + inhibits D2 receptors in VC)
5HT 3A receptor antagonist (inhibits activation of CTZ)
What class of drug can be useful in treating drug induced nausea and vomiting e.g. in Parkinsons disease?
D2 antagonists
List 6 mechanic triggers for nausea and vomiting
Chemotherapy induced Drug induced e.g. in PD Motion sickness Gastrointestinal problems Pregnancy Traumatic incident
List 2 side effects of muscarinic receptor antagonists
Drowsiness
Dry mouth
List 2 side effects of D2 receptor antagonists
Galactorrhoea
Extrapyramidal symptoms
What side effect is caused by H1 receptor antagonists?
Drowsiness (which can be desirable)
List 2 side effects of 5HT 3A receptor antagonists
Headaches
Constipation