Can drug addict get rid of drug totally?

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I have heard a bad news, one of my cousins become a drug addict. In my thought, he is a very good boy, polite and warm-hearted, but how can he turn to have drug. Now his parents try to help him get rid of the drug. But so far as I know, it is very hard to remove drug from an addict. Can he get rid of drug in his life? How can I help him?