OT:Drugs and addicts?

My mom just called me about my 21 yr old brother David. She's worried and upset about some bad things that I don't know crap about. David got out of jail this past summer. He served 90 days for getting a pot dui and then having a dirty drug test come back while in something called drug court. He was hooked on meth and other crap I have no idea about. David is my youngest brother (I have 3 younger brothers) I love them all. I was always the bossy older sister thinking I could protect the little idiots but they're grown up little idiots now and old Ange is just a bossy b word that can't keep her mouth shut. David swore when he got out that he'd get a job, stay clean. For awhile it seemed he did. He got new friends, got a job. He's been a temp at a factory in town where my other brother works.  Mom finally admitted the other day she caught him with marijuana. He told her it was hay. She's not that stupid. She called him on it and he said ok mom, its just a joint. Then she caught him with some white powder. I don't know crap about drugs. Don't know what they look like and don't care too. I used to "date" a married trucker who sold the stuff for a year but he kept it away from me cause I didn't want to be a part of that. I may not have been a angel but drugs are one thing I've not touched and I have no idea how to help mom or David. She asked me to talk to him. What do I say? I don't know what its like to have an addiction. She was asking me what she should do. Should she turn him in? I don't know. I'm afraid for her. She said he's acting funny. Anxious, excitable, eating constantly and as soon as he gorges he runs out side to puke. What in the world can I tell her to reassure her? What can I do but pray for him? If he doesn't want to give it up, how can we make him? I don't want to lose my baby brother to this crap. My brothers are all grown and I can't boss them around anymore. I can't protect them anymore. I'm feeling pretty helpless tonight. He's got a fairly decent job and he's blowing all his cash on dope. He told mom earlier today since he and my other 2 brothers live with her he'd help pay her electric bill. She said she asked him about it tonight before the boys left for work and he was like "Are u crazy?" I'm not spending my money on bills. Mom's at her wits end and her nerves aren't great. She's a nervous person. He's really hurting her. It killed her to see him in jail although I thought the little idiot deserved it. That married trucker I was with, last I heard, he was back in jail (for the 3rd time) for selling that crap. That was 5 yrs ago. He got a 12 yr sentence. My point is, once ppl start on this crap, will they ever let it go? Or do they just keep doing it? Any helpful pointers or words of encouragement would be great. Mom's email is [email protected] her name is Sharon. If u can encourage her at all I'd appreciate it from the bottom of my heart. She needs some encouragement tonight and will need it in the next few days. I'm not even sure what we can do. Hugs and Goodnight everyone Ange