Just like 56789 said - do whatever it takes. I try to keep a good, open and honest relationship with my son and I talk to him about the dangers of drugs, but they have a lot of peer pressure these days in school and with frienRAB. You cannot talk down to them or, especially, yell at them. You have to be completely supportive and say that you understand that they have a problem and that you want to help them. Tell them you want to do it together. Build a good trust with your child over this. If you can get them to admit that they want and need to get off of the drugs, it will be so much easier than doing an intervention. Get them to participate and have them want to get off of them if you can, but if you have to a a drug intervention, do it! Call the local Narcotics Anonymous (NA) and ask for their opinions also and if there are drug programs for your child available.
Good luck and keep us informed. Your child will probably go through withdrawals when they get off and the people here are available to explain what they will go through and how to lessen them. Don't just have them stop taking them - they will have to taper off depending on how much they are taking each day.