Yes this can happen, antispasmatics don't cure the problem they can just help it. They can also stop working sometimes for some people, bentyl completely stop working for me when I use to take it. I read somewhere a long time ago why this happens but can't seem to find it now, your doctor may know why that is.I don't think that happens as much though with Levsin.This is also another reason to learn relaxation techniques that can calm the spasms down, breathing, meditation, etc.. because they effect the nervous system and relax the gut which is a muscle also, even if you don't feel your IBS is stress related the real culprit in part is emotions. Although there are many triggers to IBS.