Maybe just ignoring or not responding won't make your friend go away. I've had a few "old buddies " wanting to talk me back into it- at first.
I tried the brushing off too
Finally I said -" I don't talk or associate with anyone drinking/drugging any more - period "! Hope that works .
I lost an old friend that way. Sad he didn't want to be my old sober friend , it was his choice ...