Let him fall, and let him pick up his own pieces. You cannot control his behavior and any help you give him while he is still drinking is enabling, IMO.
As for the anti-depressants...I take anti-anxiety meds for an anxiety disorder, and each type works differently for different people. He might be taking a certain kind that doesn't agree with his brain chemistry, which could certainly cause paranoia. But again, that is for him to sort out. He will continue to do what he is doing to himself until HE gets the courage and gumption to change.
Until then take care of yourself.
Hugs