Will Lysodren make my dog sick permanently?

My dog is starting on Lysodren at the end of this week. I understand
that it is chemotherapy, very strong, dangerous, and will probably
make my dog sick at the beginning.

But since he will always have to be on Lysodren (although it will be a
lower, maintenance dose), I am wondering if the Lysodren will KEEP my
dog sick forever? Or will he build up a resistance to it? Or will he
get over the initial sickness part?

Anyone have any experience with this or link to an article? I've read
a lot of info on Lysodren, but I haven't been able to find the answer
to that question. Any info would be much appreciated!