I have very much the same problem. I take between 90 to 120 mg of Mestinon daily, but it is frustrating since the amount it takes to make most of my symptoms go away also gives me twitching & shaking & nervousness.

I have talked to my doctor about this and he doesn't have any ideal solution, other than to suggest spreading my dosage out more during the day (4x 30 mg instead of 2x60mg), so I am trying it now.

For me, if I take 120 mg every day the twitching and shaking turn into muscle cramps and pain which is too much Mestinon. I have to be careful not to take too much Mestinon, but I am so thankful for it.