While the movie never really specified what drug is being cooked and sold by the bad guy, it's pretty clearly meth. At one point, the main character is forced to prepare the drug and shoot it up. To do this, she uses a lighter. I'm a recovering methamphetamine addict, and I've never seen or heard of anybody using this method for meth. For heroin, sure.
Not only that, but any real addict would make sure they're in the vein by drawing the plunger back and seeing blood be drawn into the syringe (unless they're just "skin popping" it, which is sometimes done by meth users).
Not only that, but any real addict would make sure they're in the vein by drawing the plunger back and seeing blood be drawn into the syringe (unless they're just "skin popping" it, which is sometimes done by meth users).