on·dan·se·tron 
(ŏn-dănsĭ-trŏn′)
(ŏn-dănsĭ-trŏn′)n.
A selective serotonin receptor antagonist, C18H19N3O, used in its hydrochloride form to prevent nausea and vomiting, especially when occurring postoperatively or as a result of chemotherapy or radiotherapy.
[ondan-, of unknown origin + -setron (from (se(ro)t(onin) r(eceptor antag)on(ist)).]