This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gastrointestinal tract, Subject name: Pharmacology
An antiemetic drug that also decreases acid secretion due to its action on H1 receptors is 
Select and explain. 
A. promethazine, B. domperidone, C. metaclopromide, D. ondansetron
A: promethazine
Answer: A: promethazine 
Explanation: promethazine is a first generation H1 antihidtaminic drug.it is inficated fir treatment of allergic reactions.because of its anticholinergic action and abikity to cross blood brain barrier it can be used as an antiemetic and an anti parkinsonian drug . acid secretion is reduced mainly by H2 blocking drugs like ranitidine but even H1 anti histamainics can also reduce secretion at high doses .