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
[{'content': 'A patient undergoing chemotherapy with cisplatin has severe nausea. Which of the following would be the drug to use in this patient \nSelect and explain. \nA. Scopolamine, B. Ondansetron, C. Naloxone, D. Cyclizine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 5-HT3 ANTAGONISTS Ondansetron Mech of action:- It blocks the depolarizing action of 5-HT exeed through 5-HT3 receptors on vagal afferents in the g.i.t. as well as in NTS and CTZ. uses:- Cytotoxic drugs/radiation produce nausea and vomiting by causing cellular damage - release of mediators including 5-HT from intestinal mucosa - activation of vagal afferents in the gut -emetogenic impulses to the NTS and CTZ. Ondansetron blocks emetogenic impulses both at their peripheral origin and their central relay. thus, used to control cancer chemotherapy/radiotherapy induced vomiting, and later found to be highly effective in PONV and disease/drug associated vomiting as well. Ref:- kd tripathi; pg num:-668', 'role': 'assistant'}]