The weakness at the onset is a pretty normal thing. It's a bit alarming (to me)that you were started on such a high dose. Typically patients are asked to start smaller and build up, to help avoid any big reactions. When I started I started at 10 mg daily for a week, then 20. We stopped the increase at the point of stabilization, then quickly went to every other day to help avoid side effects.

It seems to have worked, as I had fairly minimal issues with any of the side effects, except the psyche symptoms (depression, irritability, insomnia) that happen at anything over 20 mg for me. I have been up as high as 60mg and that was pretty awful (yet necessary due to my symptoms). Thankfully that was 12 years ago and I haven't been up that high since (but I've added other meds!).

You will probably feel lots better by the middle of the week, especially with the IVIG. Be doubly sure to drink lots of fluids, as the combo of steroids and IVIG will take a toll on your body. Be gentle with yourself, and talk to your infusion nurse or doctor if you have any other questions or problems.