Mechanism of Action of Apomorphine as Emetic
Apomorphine used as an emetic acts by:
- Muscarinic agonism, vomiting center
- D2 agonism, CTZ — Correct Answer
- 5HT3 agonism, vagal
- Gastric mucosa irritation
Explanation:
Correct Answer: D2 agonism on the chemoreceptor trigger zone
Apomorphine is a D2 (dopamine) agonist that acts on the Chemoreceptor Trigger Zone (CTZ) located in the floor of the fourth ventricle to cause vomiting.
Key Points on Apomorphine
- Contraindicated in cats — may cause extreme excitement.
- Can be administered subcutaneously or as a lamella (eye tablet) in the conjunctival sac.
- Since apomorphine also depresses the emetic centre at higher doses, repeated dosing is not recommended when initial dosing is ineffective.
Neurotransmitters in Emesis
- CTZ: 5HT3, D2 receptors.
- Vagal afferents: 5HT3.
- Vomiting center: Muscarinic, H1 receptors.
📚 About this Topic — Veterinary Pharmacology and Toxicology
This multiple choice question is from Veterinary Pharmacology and Toxicology, Veterinary Science. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Veterinary Pharmacology and Toxicology to strengthen your preparation.
