Persist calmly to make your point. Ask him to point out your failures from his perspective. Inquire if he comprehends the real reason drugs seem attractive. Explain that you will not tolerate continued use of illegal and self-destructive drugs. Confirm your willingness to find the proper kind of therapeutic treatment to overcome the dependency.
Idle time is the devil's playground.
Organize family activities to keep your child busy. Get him involved in community efforts to help the needy. Talk with your church about youth activities that combine spiritual and recreational interests. If necessary, insist that your child break off relationships with friends who use drugs. Go with him to concerts instead of dropping him off to see a rock band where drug use will be rampant.