I've heard of this on psych boards but have found no scientific evidence to back up the claim (that doesn't mean it isn't true, I've just been unsuccessful at finding evidence). My son takes remicade for a bowel disease. It's a biologic which is infused into him similar to chemo. It contains rat proteins. His doctor has said it's very important he not miss an infusion or the medicine could stop working all together. So anything is possible. I'm interesting in hearing from people more educated than I on this subject.