Ondansetron is used to prevent nausea and vomiting.

Ondansetron is an antiemetic medication. It works by blocking the action of a chemical messenger (serotonin) in the brain that may cause nausea and vomiting during anti-cancer treatment (chemotherapy) or after surgery.

Constipation, Headache, Flushing (sense of warmth in the face, ears, neck and trunk), Injection site reactions (pain, swelling, redness)