I would think that the cortifoam absorbs into the colon since its a foam but would ask a DR who knows. As for the urgency hours after putting it in, I have the same problems and that is why the Dr said I could use it more than once a day. It says right on the box 1-2times a day or after a BM. I really don't know how quick it starts to work but I do know from using it that it works faster than the other rectal meds for gettting the bleeding and urgency under control.
Are you taking enough probiotics during your flare, I always take alot when I'm flaring I definately see a difference when I increase them.