HI, Gabe! I've never had Ivig, so have no advice whatsoever, except perhaps to tell them to slow it down this time. But you do have all my sympathy. That degree of tiredness doesn't really sound like overdosing, especially if you had none of the other symptoms of overdose, such as excessive saliva, twitchy muscles, stomach cramps and diarrhea. I always get the twitchies especially around the eyes when I OD on Mestinon, which usually only happens if I take it without food and take it a little early. I always keep Atropine for those few times I do OD. It really helps with the stomach cramps and other symptoms. I've NEVER had extra fatigue from overdosing. I would think you would have to be REALLY overdosed to get the extra fatigue.
Hugs,