Addiction is addiction; it matters little what the drug of choice (doc) is. A substance is a substance and if he tries to tell you he's ok because he's not using one over another, don't believe him. He's quacking and just wanting you to believe it's better.
He will tell you what he thinks you want to hear. He's obviously living in the State of Denial and unless you want to become as crazy as he is, I would move quickly to another state!
Addicts are masters of disguise, manipulation, lies and theft. The drugs, regardless of what they are using, make it so. As long as he is actively "using" anything, he's an active addict! He'll use whatever he can get his hands on.
Hugs,
Marteen