I know this is not likely to be what you want to hear, but I do somewhat agree with the prior post, digmusic.
Addictions aren't easy, I know I'm a recovering meth addict. And to put it in perspective, I do know what the world's about; I'm a successful executive in a multi-billion dollar company; I have a masters degree, and I make well into a six figure salary. I'm not telling you this to brag, but to inforce the fact that addictions happen to a lot of people. People from all walks of life.
Hopefully you and your family can be there for him, but he'll have to get sober on his own. No amount of screaming, threatening, 'cutting him off' is going to do it. He's going to have to find his bottom with enough sanity to know where he is. Then he's going to have to work his way out.
That's the hardest part, where's bottom? I started using meth casually in my 30s, I was 47 when I hit bottom emotionally. Along the way I screwed up a lot of Christmasses; messed up a lot of dinner events; angered a lot of people. I contracted HIV and to make matters worst, Hep-C.
FrienRAB ask me 'how'? I don't know. When I first started using meth; it was 'fun'; (I thought) it was harmless. When everyone around me stopped casually using, I substatued 'fun' for addiction. I was hooked. I talked to a couple frienRAB and they kept saying, NO you can't be. I was! 5 years later, my health in ruins, I was able to find my sanity.
Hopefully this gives you a little more sensitivity for what your brother is dealing with. All the damage and sometimes you just don't know where you're at.
A couple simple suggestions,
Acknowledge your brother's drug use. Your talking around it, or denying it only makes matters worse. He thinks he's getting away with something, causing him to use more (high even in your presence) and getting deeper into the addiction. Acknowledging it might give him some sense to sober up in front of you. Nexted, if you can, admit your love to him, but don't enable him. Don't give him money, he'll only use it on drugs. Don't forget at Christmas it's so easy to give money. NO money! Finally, if you can, tell him you'll be there for him emotionally and mentally...but only sober. Then encourage him when he makes sobering decisions, such as staying away from drugging frienRAB or staying away from 'trigger' points. 'Trigger' points being things such as drinking to intoxication, late nights clubbing at the 'Roxy', or going to parties where he knows others will use.
I've said enough. I know it's not easy and you can only do your best. Good Luck,
doingfine