<s>[INST] context: Cisplatin is an antineoplastic commonly used in the treatment of metastatic ovarian and testicular cancers, as well as advanced bladder cancer. This medication is associated with profound nausea and vomiting; in fact, it is considered to be one of the most emetogenic agents on the pharmaceutical market. The selective 5-hydroxytryptamine-3 (5-HT3) receptor antagonists are potent anti nausea and anti emetogenic agents indicated for prevention of nausea and vomiting associated with cancer chemotherapy. Examples of 5-HT3 receptor antagonists include ondansetron, granisetron, and dolasetron. Dimenhydrinate is an antihistamine with anticholinergic activity; it is indicated for the treatment of nausea and vomiting associated with motion sickness. Dronabinol is the principal psychoactive substance present in Cannabis sativa (marijuana). The mechanism of its antiemetic action is largely unknown; it is indicated for the treatment of severe nausea and vomiting when conventional therapies are ineffective. Metoclopramide is a prokinetic agent indicated for the treatment of gastroesophageal reflux disease and diabetic gastroparesis. Since this agent blocks dopaminergic receptors in the chemotrigger zone, it is also effective in the treatment of severe nausea and vomiting. [/INST] question: A 67-year-old woman is being treated for metastatic ovarian cancer with cisplatin and cyclophosphamide. To prevent nausea and vomiting, she is given an agent that selectively antagonizes 5-hydroxytryptamine-3 (5-HT3) receptors. Which of the following drugs is this patient most likely taking? | options: A: Dimenhydrinate B: Dronabinol C: Metoclopramide D: Ondansetron | answer: D </s>