How do I get my son off drugs? He is addicted to oxycontin and he uses Ritalin which a dr has prescribed?

If his addiction is severe, you may need to check him into a residential treatment facility. As much as you want to be able to help your own son, some addictions require professional help. Talk to a professional and discuss the possibility of an intervention. There are so many treatment options out there, you just need to find the right one for your son.