Can zofran (ondansetron) help severe nausea caused by anxiety/panic attack?

Probably: Zofran (ondansetron) is an excellent medication used for nausea. If nausea is severe, it may take administration of anti nausea medication using intravenous route

Nausea/Anxiety: Zofran (ondansetron) may help, but takes time to digest & get into your system. Anxiety attacks happen quickly & therefore the treatment should be directed at controlling the anxiety. Treatments include see a mental health specialist for "talk therapy" as well as possibly taking a medication on a regular basis. If the anxiety is controlled, then the nausea & any other symptoms you may feel, will be controlled