ondansetron

Ondansetron (INN) (IPA: ) is a serotonin 5-HT₃ receptor antagonist used mainly to treat nausea and vomiting following chemotherapy. Its effects are thought to be on both peripheral and central nerves. One part is to reduce the activity of the vagus nerve, which is a nerve that activates the vomiting center in the medulla oblongata, the other is a blockage of serotonin receptors in the chemoreceptor trigger zone. It does not have much effect on vomiting that is due to motion sickness. This drug does not have any effect on dopamine receptors or muscarinic receptors.
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Ondansetron /on·dan·se·tron/ an antiemetic used as the hydrochloride salt, in conjunction with cancer chemotherapy, radiotherapy, or after surgery. [more]Ondansetron - Community and Resources

A drug that prevents or reduces nausea and vomiting. It belongs to the family of drugs called antiemetics.