can you take zofran before you start vomiting
A Stacy Wiegman, PharmD , Pharmacy, answered. Zofran (ondansetron) acts fairly quickly. For people who are undergoing chemotherapy, it is usually given 30 minutes before starting the chemo so that it is working when chemo starts. To prevent nausea and vomiting after surgery, it is usually given one hour before the operation.