I'm on day 2 of withdrawal from a slight habit of morphine and heroin, and I've been fully physically addicted before... I can't tell you what you should do, but when I'm coming down, I want nothing to do with almost anyone... or sometimes when I'm getting high, for that matter... it all depends on what he wants, what you want, and the specific circumstances between he and you. But I will warn you, that this **** sneaks up on you. I and probably he at one point could not have imagined even trying this stuff... by associating with an addict, there is always the unspoken risk that you will be vulnerable at some point, slip, try it and never come back... And there is always the chance that he or I could possibly relapse, but there is also the preferred possibility that he and you and me will be free from these wretched drugs. (They truly are pure wretchedness in disguise, please do not ever try them they cause so much more hurt than pleasure....)
In terms of getting him to seek treatment, I've found addicts to be very unpredictable about getting help... if you're able to get him to emotionally identify that his problems are caused by the drugs, it's much more likely that he will have the mental clarity to control his actions.