Well, it depends on the friend and whether they are seeking help from me. I don't have any drug-addicted friends. Normally if someone is caught up in drug addiction, then there is a negative self-image there. There are some wrong views there, wrong views towards the source of happiness and the source of suffering. If they are terribly drug-addicted, it may be that they have to go to other people that are skilled in getting them off the particular drug they are addicted to. It depends on how severely they are addicted and it depends on what type of drug they are addicted to. If it is a dangerous type of drug it may need professionals, so my actions would be to get them to the necessary professional people so that they can get off the drug in a safe way. With not so intense addictions, like we have had some students who were addicted to dope and these types of things, if they are already practicing then I can usually give the meditation on the dependent arising nature of their particular pleasure, trying to change the idea of pleasure and pain, opening to Dukkha. The smoking technique that we give starts to do that. Knowing the desire, feeling it in the body, feeling compassion and using various reflections, especially those to help them see the decay of the lungs, or to see themselves in a coffin. These types of things help to change the pleasure into the Dukkha so that they see the possible consequences of their addiction.
Sometimes when people are psychologically addicted they will try to justify it by claiming that is doesn't hurt anybody. Opening their mind to the suffering of the beings involved in getting that drug to them helps them to change their view of the particular pleasure that they have and helps them to see the Dukkha that is involved with that. It is similar to the food reflection.
We had a friend who took his alcohol addicted friend by force to get dried out. It worked, but apparently the friend doesn't talk to him any more... obviously he hasn't learned how to be grateful yet. When one student kept going back to drugs and alcohol I asked them, "Did they know the prerequisites for being reborn a human?" No. It is the Five Precepts. And the fifth precept is not to take drugs that control the mind. So immediately the idea of alcohol shifted from pleasure to pain. Sometimes we have to change the idea of the pleasure into Dukkha. Get them to open to Dukkha. This particular student has been dry for along time now because one of the things they don't want is to be reborn any lower than human. So if a person is Buddhist it can help them to change the view.