First of all welcome to PC.

I think that you need to take care of yourself first and foremost. The stronger you become and deal with your own depression, the better you will be able to help your friend.

As for your friend I would have a serious conversation about what is going on with him and what options are out to help him get better--when he is sober. I would also give him the spiel about how mental illness is nothing to be ashamed of.

I hope I helped, and feel free to PM me if you want to talk