Our favourite routine with violent and abusive patients in the military - yes we had our fair share of drunks and morons - was as follows: Medic: Doctor, can I put the drip up/give the patient the injection. I've never done it before. Doctor: Of course you can. Just try not to rupture the vein/make sure you don't push through to the bone. It was amazing how the patient would just behave themselves after that exchange.