Sorry it took me so long to respond...

Yes I have taken Prednisone for Myasthenia. it is very tricky - can improve MG by suppressing Immune system but can cause weakness. It would be good to see someone familiar with MG because they would have a little better idea how to deal with it. i was on Prednisone for 8 months and alternated doses 5mg one day and 40 mg the next...I started at a higher dose every day to get things under control, then tapered off on the low day until I was down to 5mg...the belief is that by alternating high and low dose days there are fewer long term side effects. When I went to the University for tests they took me off all of the Prednisone quickly (over the course of 1 month) - that was too fast! I was very weak, achy, exhausted, and it took a long time for my adrenal glands to kick back in.

I know they use high doses of steroids when people are having a breathing crisis and it is short-term.

You probably need to talk with your doctor about dosages - not sure if you were planning to reduce the dose baased on his order or not...I think there are specific guidelines about how much the dosage should be decreased at a time.
Good luck,
Gabe