There's nothing you can do. You can say something to the person, but he or she will get mad at you and it won't really make a difference. What you CAN do is decide what your own boundaries are. Know that as it turns from drinking problem into addiction, the person WILL lie to you.
One of my best friends died from alcoholism and other addictions. It was pretty horrible. Many of us who cared so much about her confronted her, helped her, listened to her, etc., etc. Eventually, each of us reached a point where we told her, "Call me when you've been sober for 6 months." When I stopped speaking to her, she was driving drunk on a daily basis and showing up to work drunk...she was a school teacher. She lost her job, her home, her car, went to rehab a few times. Her parents paid for a couple of those stints in rehab. At the end, she was homeless and died in a public park. The addiction stole her away.
I hope to God that the same doesn't happen to your friend. I hope your friend figures it out and gets medical help before it becomes a raging out of control beast that takes over everything.