Mainlining a drug into your bloodstream, drawing back the syringe to refill it with blood, and then injecting it back into your arm. The theory being, the blood injected back into your bloodstream, will carry with it, any residual narcotic leftover in the syringe.
Yeah, but it's not common.
Especially when they're booting it.
And yes, it's possible to take the pills and turn them into a form that can be injected. It's very disturbing.
I just looked up booting and I regret it.
From urbandictionary:
Nah that's wrong. You only draw the plug back to make sure you're in a vein, blood coming into the syringe confirms it's in there.