en bloc, At a really high dose, mestinon can cause a cholinergic crisis which weakens muscles, breathing ability and other symptoms. That would need to be treated in an ER. I doubt your doc would prescribe enough to cause that but I am not a doc and don't know your situation. At a slight overdose you could feel muscle twitching and other side effects mentioned above. I think mestinon is pretty benign once you see how it feels and learn how to use it. Talking with your docs to adjust dose and frequency of dose will get you there quickly. My neuro prescribes it for several neuro-muscular diseases including MG and ALS.

I'm careful to never take more than the 60mg per 4 hours my neuro prescribed. I've also been told it's OK for me to take 30mg every 2 hrs if I feel that works better. I bounce between the two schedules depending on how I feel. If I'm not doing well, I take the higher dose and wait longer for the next dose. I have felt some muscle twitching from it but that passes fast enough to not bother me much.

I can't know why your doc would be so worried except it sounds like he's recommending mestinon 'off label' for a condition it isn't routinely used for. If you were really worried, it wouldn't be unthinkable to 'camp out' in the hospital cafeteria for a few hours when you took your first dose. Just an idea.

Good luck. It doesn't help everyone who takes it. I hope it helps you.