When I took IV IgG, I took benadryl and Aleve. The non-steroidals ibuprofen (Advil, etc) or naproxen sodium (Aleve, etc) help with the headaches a lot more than tylenol alone, if you can take them. It may help to take oral benadryl and non-steroidal around the clock for a few days starting the evening before and continuing until at least a day or so after the IV IgG infusions are done. Steroids are a different kind of anti-inflammatory medication. Can you tell us what your reaction was with prednisone? It might help us to be able to give some suggestions. Any reaction with steroids can be linked to the dose that was given. Dexamethasone is about 20 times stronger than prednisone with respect to effect per milligram (mg). It also has a better ability to get into the fluid around the brain and so probably works a little better with the headaches and nausea side effects of IV IgG. A lot of the kids that get IV IgG for autoimmune diseases get decadron premedication to help prevent reactions and it tends to work pretty well–most of the time the dose in about 0.5 to 1 mg in these little ones which would correspond to 3 to 5 mg in adults. I have seen adults given 10 to even 20 mg with IV IgG. Both of these are a lot and likely one would get moody and have trouble sleeping with this much. I took a pretty small dose of decadron (dexamethasone) before for another reason and felt jittery and irritable (not my usual state). If it prevents the severe headaches and vomiting, it will be probably be worth it.
I meant also to say that for some, changing the type of IV IgG can alter the severity of the reaction as some people react a lot more to one brand than to another.
WithHope for a cure of these diseases