Antiemetic is a drug that is effective against vomiting and nausea. Antiemetic Drugs may also be used to treat nausea and vomiting caused by other medications, frequent motion sickness, infections, or stomach flu. This may include drugs for anesthesia used during surgeries or chemotherapy for cancer. Antiemetics can be categorized based upon their mechanism of action. their receptor activity or their chemical structure. Antihistamines have mild antiemetic activity and are commonly used for motion sickness and the transient nausea. that might accompany a viral illness or gastrointestinal infection or disorder.