Had 1st infusion 3 weeks ago and felt better by next day; less stiffness and pain. But on the 5th day I woke up with a terrific headache and diarrhea which lasted four days. Then stopped and felt really much better. Going for my 2nd infusion next week and wonder if this is one of the side effects? I've read several reviews and didn't find this at all. If this is the only negative effect, I can live with it. I'm beginning to feel normal again and can function doing my daily chores. Simponi Aria is a miracle for me.