PAC3421 Study Guide - Final Guide: 5-Ht3 Receptor, Chemoreceptor Trigger Zone, Muscarinic Antagonist
21 Jun 2018
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Vomiting/Emesis
Which of the following drug classes are most commonly used to treat motion induced vomiting?
a. 5‐HT3 receptor antagonists
b. D2 receptor antagonists
c. H1 receptor antagonists
d. Muscarinic receptor antagonists
e. Both C and D
Which ONE of the statement is CORRECT?
a. The antiemetic action of D2 antagonists is via their blockade of D2 receptors in the vestibular
nuclei.
b. The antiemetic action of 5HT3 antagonists is due to antagonism of 5HT3 receptors in the
chemoreceptor trigger zone but not due to peripheral 5HT3 receptor blockade (feedback: Some
peripheral blockade of 5HT3 antagonists occurs and is thought to be anti-emetic)
c. In treating motion sickness, muscarinic antagonists block muscarinic acetylcholine receptors
(mAChR) in the vestibular nuclei
d. None of the above
Rationale for drug use in vomiting:
Relieve symptoms
Prevent symptoms
Prevent complications (i.e. dehydration and electrolyte disturbance)
Anti-emetic drug summary:
Drug Examples Receptor site Indications
D2 antagonist Metoclopramide
(contraindicated in bowel
obstruction), domperidone (+
prokinetic effect)
Gut, CTZ, NTS Nausea and vomiting
due to gastroparesis
(i.e. poor gastric
emptying and
constipation)
H1 antagonist Promethazine, pheniramine,
dimenhydrinate (+ hyoscine),
cyclizine
Vestibular nuclei, NTS, VC
Antipsychotic (D2,
H1, mAChR
antagonist)
Prochlorperazine,
promethazine
As above
Antispychotic 2.0 Benzodiazepine (e.g.
alprazolam, lorazepam)
Nausea and vomiting
due to anxiety,
anticipatory, smell
mAChR antagonist Hyoscine (or scopolamine) Vestibular nuclei, CTZ,
NTS, VC
5HT3 antagonist Ondansetron, granisetron,
tropisetron, palonosetron
Gut, CTZ, NTS, VC CRINV, PONV
NK1 antagonist* Aprepitant OR fosaprepitant Gut, NTS, VC Add-on for severe
CRINV;
Corticosteroids Dexamethasone Intracranial Raised intracranial
find more resources at oneclass.com
find more resources at oneclass.com
pressure from
intracranial tumour;
add-on for CRINV;
PONV
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Which of the following drug classes are most commonly used to treat motion induced vomiting: 5 ht3 receptor antagonists, d2 receptor antagonists, h1 receptor antagonists, muscarinic receptor antagonists, both c and d. Metoclopramide (contraindicated in bowel obstruction), domperidone (+ prokinetic effect) Nausea and vomiting due to gastroparesis (i. e. poor gastric emptying and constipation) Nausea and vomiting due to anxiety, anticipatory, smell machr antagonist. Raised intracranial pressure from intracranial tumour; add-on for crinv; Nancy is a 40-yo female currently undergoing radiotherapy and chemotherapy for a tumour in the brain. She is currently on a regimen consisting of procarbazine, lomustine (ccnu) and vincristine. Chief complaint (cc): patient is suffering from severe nausea and vomiting. Hpi: patient has been feeling extremely nauseous and threw up a few times today 3 hours after treatment. Patient is also complaining of severe pains and high fever. C&s found bacterial growth and patient was started on an antibiotic and was given morphine for pain relief.
