I got quite sick after my second rituximab infusion (fever and vomiting) but it passed within 24 hours.

They gave me Piriton and paracetamol during the infusion to help with side-effects but I have heard some doctors also give some extra steroids?

As for how long it takes to work, my B-cell-count goes to zero within days. But symptoms-wise, the first time I had it, it took a month or so to help. That initial treatment was as a steroid-sparing agent and to give some extra help while I was reducing my Cellcept dose. The second time I had it though (9 months ago) it was to try and help treat a flare and it hasn't helped my symptoms at all. I'll get another dose when my B cells return.

Hope that helps!