What medications are you taking besides Mestinon? I always take my Mestinon with food, if I don't I sometimes get overdose symptoms. With me, these take the form of twitching muscles, especially around the eyes, and stomach cramps and diarrhea. I always keep a prescription of Donnatal on hand in case the overdose symptoms are really bad. I rarely take it, but I like to have it. Actually, at the moment what I've got is the generic, which says it is Bella ALK/PB. It is actually Belladonna, or atropine, and it is basically the antidote of Mestinon, and is used to control side effects of Mestinon.
Hugs,