He is addicted to drugs and wants to repent

My sister's husband uses drugs. Although he wants to stop using it, he can't because of his addiction, but elhamdoulillah he fears Allah swt.
My sister wonders what to do in this situation, she has 3 children with him, and leaving him would be worse because then there wouldn't be anyone for him so he could go and use more & or commit suicide etc..
I ask you for help with the power of the "One" in whose hand my life is.

Praise be to Allaah.  

We advise your sister to stand by her husband in his repentance and attempt to rid himself of addiction to drugs, and not to leave him to the human wolves who would destroy him. He needs her more than ever right now. 

You have to seek help from medical centers that treat addiction. There is nothing wrong with that, because this will help him to get rid of his addiction. 

She should not hesitate in that, and she should hasten to get in touch with those who specialize in dealing with such matters. But she should always remind him to be pious and fear Allaah, and remind him of death and the meeting with Allaah, whilst encouraging him to give up his addiction and giving him the hope that he will recover and his repentance will be accepted by his Lord. 

Please also see the answer to question no. 6540. 

And Allaah is the Source of strength.