He'll snap out of it in time. You may want to be his driver in the mean time.
your friend will die
Alcohol is a depressant. Tell him to get hi on life.
It's his coping mechanism, and he'll snap out it eventually. I would suggest keeping an eye on him when he's been drinking heavily and be his designated driver until he snaps back to reality.
It's not unusual for people to drink heavily after a bad breakup. Just make sure that you're a good friend and supportive and try to help them find other things to do than drink heavily to forget.
I'm sorry for your friend. It isn't healthy for him to keep drinking heavily so he needs to find a distraction to break it before it becomes a dependency. He needs to see that there is life after a breakup.