In my experience the drug of choice does not matter because when I attend Al-Anon the focus is on _me_ and how I respond or relate to other people, places and things. That's what I need to do whether someone I love is using/drinking or working a program of recovery. The people closest to me are in recovery and doing well, yet I find that more than ever I still benefit from attending Al-Anon.
It's a wonderful program, I hope you give it a try.