Zofran (ondansetron) is an antiemetic and selective 5-HT3 receptor antagonist prescribed for the treatment of nausea and vomiting due to cancer chemotherapy and also used to prevent and treat nausea and vomiting after surgery. Zofran is available in generic form. Common side effects of Zofran include: diarrhea, headache, fever, lightheadedness, dizziness, weakness, tiredness, drowsiness, constipation, rash, blurred vision, and; muscle spasm. Zofran adult dose is 32-mg given as a single dose or divided in three 0.15-mg/kg divided doses infused over 15 minutes.