Anti Emetics Flashcards
Name a muscarinic receptor antagonist
Hyoscine hydrobromide
What are muscarinic receptor antagonists best for?
Motion sickness and bowel obstruction
Side effects of muscarinic receptor antagonists
Sedation, memory problems, glaucoma, dry mouth and constipation
Name three H1 receptor antagonists and their use
Cyclizine - GI problems
Cinnirazine - Vestibular disorders
Promethazine - Morning sickness
How do H1 receptor antagonists work?
Block histaminergic signals from the vestibular system to the CTZ in the medulla
Side effects of H1 receptor antagonists
Sedation, excitation, dry mouth, constipation, urinary retention, long QT interval (cardiac toxicity)
Who is cyclizine not suitable for?
Little children and elderly people
What is the effect of serotonin in the gut?
In response to parasympathetic excitation, serotonin is released which excites enteric neurones. This leads to:
- Smooth muscle contraction, increasing motility
- Increased gut secretions
How do 5HT3 receptor antagonists work in the gut?
They reduce GI motility and secretions, and inhibit the CTZ.
Name a 5HT3 receptor antagonist
Odansetron
Side effects of 5HT3 receptor antagonists
Constipation, headache, elevated liver enzymes, long QT syndrome, extra pyramidal effects
Name 2 D2 receptor antagonists that act on visceral affects on the gut
Metoclopramide, domperidone
How do D2 receptor antagonists (gut acting) work?
They increase Ach at muscarinic receptors at the gut. This promotes gastric emptying by increasing tone at LOS and increases gastric contractions. It reduces tone at the pylorus. Increases peristalsis. (prokinetic)
What are D2 receptor antagonists (gut) used for?
GORD, ileus
What are some side effects of metoclopramide?
Galactorrhoea via prolactin release, extra pyramidal effects
What are some side effects of domperidone?
Sudden cardiac death (long QT and VT), galactorrhoea
Name 2 D2 receptor antagonists that work on the CTZ
Haloperidol and chlorpromazine
What is haloperidol good for?
Chemotherapy and palliation
What are side effects of the CTZ D2 receptor antagonists?
Extra pyramidal effects, sedation, hypotension
Name two corticosteroids
Dexamethasone and methylprednisolone
How do corticosteroids stop nausea?
They act on the CTZ
What are corticosteroids good for?
Perioperative nausea and vomiting, chemotherapy, palliation
What are some side effects of corticosteroids?
Insomnia, increased appetite, increased blood sugar
Name a NK1 receptor antagonist
Aprepitant
How do NK1 receptor antagonists work?
They prevent substance P release at the CTZ, boosts effects of 5HT3 receptor antagonists.
What are some side effects of NK1 receptor antagonists?
Headache, diarrhoea/constipation, Stevens Johnson syndome
When are NK1 receptor antagonists used?
Chemotherapy
When should you not use D2 receptor antagonists?
Obstruction or risk of perforation
What is the treatment algorithm for GI related vomiting?
Ondansetron and/or cyclizine, then add dexamethasone
What is the treatment algorithm for hyperemesis gravidarum?
Promethazine or prochlorperazine, then add metoclopramide, then add odansetron
What is the treatment algorithm for chemotherapy N+V?
Dexamethasone, maybe with odansetron, maybe add aprepitant.
Add metoclopramide for rescue
