Physiology and Pharmacology of Vomiting - Week 3 Flashcards
What is meant by retching?
rhythmic reverse peristalsis of the stomach and oesophagus without efflux of vomitus
Vomiting is co-ordinated by…
by the vomiting centre (VC) in the medulla oblongata of the brain stem
Vomiting is usually preceded by….
profuse salivation, sweating, elevated heart rate and the sensation of nausea
Where do contractions span during vomiting?
Contractions from ileum to stomach
What is the state of the sphincters during vomiting?
Open (relaxed)
Explain how toxins cause vomiting.
Toxins stimulate Enterochromaffin cells in mucosa to release mediators such as 5-HT cause depolarization of sensory afferent terminals in mucosa. Results in action potential being discharged along the vagal nerve to stimulate the vomiting centre.
Pharyngeal stimulation, gastric/duodenal distension, or irritation triggers which structure before the vomiting centre?
NTS
Toxins trigger which structure before the vomiting centre?
CTZ
Give some consequences of severe vomiting.
Dehydration, metabolic alkalosis, hypokalaemia, oesophageal damage
Give some examples of drugs which may cause Emesis.
Cancer chemotherapy, general anaesthetic, dopamine agonists, morphine & opiates, digoxin
What is the major class of anti-emetic drugs?
5-HT3 receptor antagonists
5-HT3 receptor antagonists always have what in their name?
‘Setrons’
5-HT3 receptor antagonists are primarily used to…
suppress chemotherapy- and radiation-induced emesis and post-operative nausea and vomiting
How do 5-HT3 receptor antagonists work?
Block peripheral and central 5-HT3 receptors
Give examples of 5-HT3 receptor antagonists.
ondansetron, palonosetron
