It sounds like it could be the beginning stage of alcoholism. Toward the middle stage, there start to be consequences, like missing work, DUIs, saying/doing things they regret while drunk, deteriorating relationships. Is he driving home plastered?
I would just ignore him when he comes home hammered. Sleep in a different room and use earplugs so he doesn't wake you up, and don't help him out at all. Tell him that you need your sleep and that he is not to disturb you. If he doesn't like it, go to a hotel room the next time he goes out drinking. He might take you seriously after that.
How often is he getting drunk like this?