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
