You say there's an injectable form of naltrexone. I'm not an expert, but I know that there's a molecule called buprenorphine, which, according to your presentation, seems to have the same effect, and it's available in Canada.
These substances would make treatment much easier, since they're injected once a month and completely change the way the person's brain works. We know that a drug addict's world revolves around their daily use, so if they have everything they need to avoid experiencing adverse effects for a month and are even protected from overdoses, that changes the situation.
Why not focus heavily on that solution?