I have TERRIBLE D. The only thing that really worked well for me was Lotronex and Remeron (another 5ht3 blocker). I HATED the Zofran. It made me feel worse than ever. It made my IBS worse when taking it. I felt better without drugs at all compared to taking the Zofran. So, I donated all of my Zofran to a Cancer Center. If you decide to try Zofran and it fails - I would suggest donating it to cancer patients who do not have health insurance. Zofran is VERY expensive.I would highly suggest Remeron or Loprodomide (prescription Immodium) verses Zofran. That is just my personal experience. It does make many people crampy all day though.Good Luck