The fact that you are letting him drive your car while he is completely drugged up scares the heck out of me - because that used to be me.
Until he wrecked my car because he fell asleep at the wheel - with a crack pipe in his mouth. Got busted by the police. Ended up in jail that time. I paid several thousand dollars to get my car fixed.
What was crazy was that about a year later, I got pulled over and they asked me where he was because he had a warrant out of his arrest. I asked the police how they knew I knew him. Turns out that my license plate number associated with him in the police data base. I sold my car shortly after that. But yes. These things can and do happen.
I'm just glad he didn't kill someone when he was driving my car. I never would have forgiven myself. Please don't let him drive your car anymore. Set some boundaries. You will come to regret it if you don't.