It's an herb (actually, it's ground up bark from the plant). You can get it from GNC or health food stores or any place like that. It's pretty easy to find. Price-wise, better quality is obviously going to cost more, but I got a bottle of 100 pills for $10 or $15. I don't know what quality it is, but it's good enough that it works, and that's all I really care about.
The only side effects we've had with it were the occasional headache, and occasionally feeling like we've had too much caffeine (yohimbe's a stimulant, too). But you do want to stay away from it if you've got heart or blood pressure problems, especially if you've got low or irregular blood pressure, since the yohimbe actually lowers it. So if you've got hypotension and then you go take something that lowers your blood pressure even more, you're kind of screwed.
