Antiemetic action is due to which propey of metoclopramide?
(A) 5-HT3 antagonist (B) D, antagonist (C) 5-HT4 agonist (D) M3 antagonist
(B) Ans: B. D, antagonist(Ref: Goodman Gilman 12Ie p1325; Katzung 13/e p1062, 12Ie 0092; KDT 7Ie p665).Metoclopramide:Dopamine D, receptor antagonist.Mixed 5-HT 3 eceptor antagonist & 5-HT, receptor agonist.Antiemetic action due to its antagonist activity at D2 receptors in the chemoreceptor trigger zone in the central nervous system-this action prevents nausea & vomiting triggered by most stimuli.At higher doses, 5-HT, antagonists activity may also contribute to the antiemetic effect.