Hi,I took Zelnorm for a short time awhile back, and although I did not notice a difference in my cycle, I am also on birth control pills. However, the Zelnorm should not be affecting her cycle and she should probably go see a doctor about that. Zelnorm's side effects do not list that from what I remember. However, it's only been on the market for a bit, so there could always be different things that may not have come out yet? I'd look into that, just in case.