Managing harm, as you suggest, is the best way to handle things going forward. It also covers a lot of things beyond drugs, things that are addictive for some people like gambling.
In terms of priorities it should be avoiding harm to others, such as not driving under the influence as you suggest, and then avoiding harm to the individual, as might be the case with a chronic alcoholic.
As a note, heroin isn't as inherently harmful as it's made out to be, but, like other things, so long as it's illegal it will really only be popular with the more hard-core drug users. It was legal before, after all.
In terms of priorities it should be avoiding harm to others, such as not driving under the influence as you suggest, and then avoiding harm to the individual, as might be the case with a chronic alcoholic.
As a note, heroin isn't as inherently harmful as it's made out to be, but, like other things, so long as it's illegal it will really only be popular with the more hard-core drug users. It was legal before, after all.