I've been having the opposite problem the last two times. The first week, I feel kind of off and a little achy. The second week, it's urgency, multiple trips to the toilet, explosive diarrhea, incomplete emptying, and this time around, blood. The third week, everything calms down, and then it starts to wear off around the sixth week, but my only real symptom then is joint pain.
I say real symptom because I only had formed stools the first couple of weeks with Remicade.
I'm on it mostly for the joint pain, but it doesn't seem to be controlling the UC very well.
On the upside, I used to have this stubborn dermatitis on one of my fingers. It went away the day after my first infusion. It comes back around the seventh week, and goes away immediately after the infusion. Strange.