I was on loxapine for quite a while before it became painful enough that I realized it was a problem, even though I knew to be looking for it and had a script for cogentin in my purse. I think 2 months or so and the soreness probably started around 4 weeks, maybe sooner. And when I had EPS from Geodon I'd been on it probably 3-4 months. It usually happens early in treatment but "early" isn't defined and also there are always outliers.