Edited excerpt from the discussion:

DR LEONARD: Allergic reactions to rituximab are rare. The spectrum of what is an allergic reaction versus what is an infusion reaction overlaps. It’s hard to say one way or another. Most patients will tolerate rituximab without a problem, but in this situation, the questions are: How hard do you want to work at it and how important is it?

One approach would be to admit the patient to the hospital and give the rituximab over 24 hours, which we have done on occasion. However, that is inconvenient for both the patient and physician.

I would do what John Byrd has done in CLL. Perhaps pre-medicate with a steroid and then give 40 or 50 milligrams of rituximab over three or four hours. Then give another 50 or 100 milligrams the next day, perhaps dividing the dose over three days to see how the patient responds. If the patient is tolerant, then you know that it is not an allergic reaction, and you will probably be able to give subsequent doses more quickly.

DR LOVE: What’s the mechanism or pathophysiology of an infusion reaction versus an allergic reaction?

DR LEONARD: Most infusion reactions are related to complement and the fact that you are binding B cells, which activate complement. When more circulating tumor cells are present, greater complement activation by B cells occurs, which leads to more cytokine activation.

I’m not certain that steroids help much in preventing infusion reactions; however, in a patient like this, when you don’t know exactly what you’re dealing with, you need all of the help you can get. Give this patient plenty of diphenhydramine and some steroids.

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