My 15 year old son was put on prednisone for orbital pseudo tumor...

My 15 year old son was put on prednisone for orbital pseudo tumor about 5 weeks ago.He hasn't had many side effects except vomiting and the pattern seems to be every other day he has tapered down from 40 mg. to 20 mg. I thought maybe the pseudo tumor might be causing vertigo , i don't know if vertigo is sporadic like this? The vomiting didn't begin until right before his next day reduction on his prednisone. I don't know what to think of this drug at this point ,it did make his eye which was swollen completely shut, begin opening up about 5 hours after his initial dose of 40mg.But i don't know why he is vomiting off and on and it didn't completely stop his eye from hurting. Now the doctors want to biopsy his eye muscle since he is not responding well to prednisone reduction.God be with you all who are struggling with this medicine.