I was diagnosed with MG 6 years ago. My neurologist happened to be a specialist with this disease. I was started out on 30 mg of Mestinon every 3 or 4 hours (its been so long, I don't remember the exact time span). The only side effect I had was stomach cramps which only lasted about a week. It worked great for about 4 months but I began having a difficult time talking. My tongue just didn't want to help form the words. The Mestinon was increased to 60mg and then up to 120mg without much of a change. My doctor then put me on Cellcept, 500mg twice a day. And I am doing just great! No side effects whatsoever. Although, as with any immune suppressant, you need to be diligent taking care of yourself. There are a number of side effects to be aware of but they are truly worth the small risk.
The *edit* is a great resource for information also.