There is a reason that patients like methadone and hate naltrexone. That is, methadone activates opiate receptors and causes a "high" (at least until tolerance develops) while naltrexone blocks them and may, in some cases, prevent even natural highs caused by normal activation of these receptors.
Now, nothing in the brain is simple and it is quite possible that blocking opiate receptors in the short term may have a positive effect on mood in the long term (and the short term "pleasant" drugs may be unpleasant long term, conversely. Also, some of the problems associated with addiction may result from overgrowth of these receptors and so blocking these "extras" may reduce craving.
But it's a hard sell to tell addicts, you've been enjoying this drug-- now we're going to give you one that makes it impossible to enjoy it and may interfere with other pleasures. And we're going to implant it so if you have side effects, tough noogies. That's a stupid way to sell a drug and the only "buyers" are going to be the desperate and the enforcer/moralists who love the idea of a drug that will deny these evil hedonists their fun.
And, the truth may well be that some people become heroin addicts in the first place because they are deficient in their natural opioid systems-- so methadone works for them and naltrexone makes them worse because their problem was a lack, not too much.
Anyway: the bottom line from the research seems to be that there's a tiny minority that can be helped by naltrexone (many studies find it simply has no effect on heroin addiction relapse but some addicts report remarkable anticraving effects) and they should have access to it (with warnings about overdose issues and access to naloxone in case they do OD) and a larger group can benefit from methadone and they should have access to it (and not the crazily restricted access we currently give) and people need choices to recover.
Interestingly, naltrexone seems much more useful for alcoholics-- it may actually help them moderate drinking because it's much more effective at reducing craving for "more" once you've had one than it is at preventing you having one.
Our crazy view of "this drug is evil" and "this drug is wonderful" precludes sane drug policy.
