The only way you can help a friend to stop taking drugs is to encourage them to visit a Therapy Centre. Depending on the nature and depth of your friendship, you can then support them in their efforts by providing them with emotional support and seeing that they stick to their pledges.
Remember that you are definitely not helping an addict by giving them money, which only makes it easier for them to continue taking drugs. The next time you meet your friend, you could make it clear to him that you have no intention of helping them stay addicted! If you need more information, you can call the KETHEA ITHAKI Helpline (1145, local rates apply).