Because chemotherapyterm is such a harsh treatment on the body, the body reacts to these poisonous chemicals and tries to rid the body of them. One way the body responds is through a vomiting action preceded by a nausea feeling. Because the continuation of treatment is critical in chemotherapy and since nausea and vomiting is a common side effect, antiemetics are used to prevent or lessen the nausea and vomiting mechanisms. Antiemetics are compounds that prevent emesis, otherwise known as vomiting. Antiemetics function through various molecular pathways and are classified into categories by their target. A key aspect to understanding the function of antiemetics is the structure of the nervous system signaling pathway as it relates to nausea and vomiting.