What can I do to help my son?

So long story somewhat short… He’s 20, regular user of medical marijuana that he has his card for. Last fall he used cocaine over a period of a few weeks. He admitted it and said he was done. Which he was until February when he probably used for about a week (he tells me after the fact so that I can help him). Today he admitted to buying morphine pills and taking one last night. He is giving me them to dispose of when he gets home from work.

I don’t want this to spiral and I don’t want to lose him. How can I help him?