Beannie, When I first started on mestinon it gave me terrible gas and diarrhea. Was sent to a gastro Dr and even had an endoscopy but still had problems with the mestinon. I finally figured out it was the amount of mestinon that was the problem. Switched to half the dose, half a 60mg every four or so hours and the problem was solved. When the MG symptoms are more intense I am able to tolerate more mestinon. Worked for me. Best of luck to you.
AL