Hi,
I'm new to the group .... I'm also fairly new to myasthenia gravis, stiff-person syndrome and POTS dysautonomia.
Anyway, that drug is definitely heavy duty and I personally wouldn't start there at all. It's extremely concerning to hear that you're having that much trouble breathing!
What city/state are you located in? My doctor is in Dover, NH and he saved my life just in time. The MG has a good hold on my lungs and you need to be extremely careful if in fact it is MG attacking yours!

I started with a low dose and quickly titred it up - MESTINON. My doctor immediately set me up for IVIG infusions in my home. This is the standard treatment.

You should know pretty quickly when you take the Mestinon - I know I felt improvement in my breathing and my muscle weakness right away.

Go to the ER about your breathing. Ask the hospitalist to please give you a trial of Mestinon while you're there at the hospital so they can supervise you. Ask them to call in a neurologist to do a consult.

Don't wait on your lungs - please. Educate yourself as much as possible.

God bless,
Kelley Z