Erin,
This kind of reaction happened to me with Mestinon, and no amount of food helped me. Mestinon has a Lactose filler in it, and if you are lactose intolerant, it can really cause you some trouble. It all depends how sensitive your body is too it. I was constantly in the bathroom. It was awful.
My doctors prescribe Welcol tablets, and they help a lot.
There is also an alternative called MYTELASE. I just heard about it last week. It's been around since the 50's, but for some reason doesn't get much press. I'm going to ask my doctor about it in a couple weeks.
Love Lizzie