I'm not AT ALL surprised that this topic hasn't seen a single reply. Aside from being COMPLETELY dangerous, it's just plain stupid.
I can't, for the life of me, figure out why anyone would shoot ANYTHING, especially medication that's meant for oral ingestion. In this case, your friend is signing his own death certificate (and you were as well). I'm glad you quit. Being someone who DID stop, why don't you convince your friend to stop as well? I would ASSUME that you stopped because you realized how dangerous it was. If, ofcourse, you stopped for other unrelated reasons, I guess it would be hard to convince anyone to stop.
Regardless of anything, even though I don't know you or your friend, I sure hope he gains some knowledge and stops what he's doing (essentially killing himself). Nobody deserves to die.