Yeah this is getting way off topic but it can cause tons of fucked up shit to happen, such as brain stem dysfunction, severe vasoconstriction etc.. Sure people do it, but the only reports of people dying from propylhexadrine that I've found, have been people who have used it I.V. No drug is safe to inject, especially street drugs, or poorly filtered pharmaceuticals. But some are definately more dangerous than others, and propylhexadrine is one of them.
Anyway, like I said, I've only found one or two posts online about injecting 6-apb, both were not necesairily reliable, but ine said that it was a pain in the ass to do (I'm guessing poor water solublility)l and the other warned that it might have similar dangers of injecting that propylhexadrine does. Bottoms line is: you never know what's going to happen with RC's, no matter which way you consume them. But injecting them is not safe and no one can tell you what to expect (thus far at least).