You have to do all that you can to get him out of it. Yukti (skill), Shakti (strength), priti (love); with love, skill and through some force, somehow, you must help him to get out of it. The best thing is to put them in a rehabilitation home.
We have one in Kolkata, and there are many other rehabilitation centers all over. Take him to such a center, make him do the Sudarshan Kriya.
If he learns the kriya and pranayama, it makes a big difference. Many people have left drugs and alcohol when practicing the Sudarshan Kriya.