I've never heard of anyone building up a tolerance to IVIG. Perhaps you just need a higher dose. I definitely feel better with more, I just can't tolerate the side effects. The dose I'm on is what I can do without side effects. When I was in crisis in January, I got three days instead of two while I was in the hospital and it made me feel better. My vision got nice and crisp. I wish I could get three days all the time! But in all honesty when I'm doing really well I can do fine on two days every three weeks. At least I pulled that off for about 3 months this fall, so that's my story and I'm sticking to it!

I take Mestinon as well but I don't think it really does a thing for the MG. I also have POTS and it helps that a great deal though.