<prompt> A patient undergoing chemotherapy with cisplatin has severe nausea. Which of the following would be the drug to use in this patientScopolamineOndansetronNaloxoneCyclizine  <response>: 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 drugsradiation 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 chemotherapyradiotherapy induced vomiting, and later found to be highly effective in PONV and diseasedrug associated vomiting as well. Ref:- kd tripathi; pg num:-668 