In my experience, Abilify worked quite quickly; there was no waiting 6 weeks to see if it helped.

I know that Zyprexa, another AP works right away as well because I take it for "rescue"; if I am on the verge of needing to go IP, pdoc wants me to take 20 mg Zyprexa and go to bed instead of going to the ER. It pretty much knocks me out but it does end the SI.