A bit more on addiction:
If an addict was “clean” for 2 years (the deserted isle scenario) and went back to civilization it would, in my mind, be a toss up whether they’d go straight back to a dealer or not. As pointed out, addiction is more than just the physical. You can throw anyone in a rubber room and detox them physically, but that’s not a cure. Mentally, they’re still an addict.
Methadone does not have “worse” withdrawal… it has a longer withdrawal than heroin for the simple reason it leaves the body at a slower rate. Going cold-turkey off either isn’t pleasent, but with heroin the process is over with significantly quicker.
In theory, the idea with methadone is to get the addict “stabilized” - niether high nor in withdrawal - with a single daily dose that does not involved the rituals of shooting up (the ritual itself can become reinforcing - also, methadone maintenance was started in the US back when needles were the method of choice, unlike the snorting and what not that can occur these days). Then you do the mental work of unraveling the reasons for addictions and mentally preparing the person for giving up the drug of choice for good. Then you take them off it slowly, to minimize the unpleasentness. And when I say slowly I mean it might take a year or two to taper the dose down to nothing. That dose has to come down that slowly or yes, a person could wind up in withdrawal and you want to avoid that, because it can re-trigger the urge to use. Done properly, with a cooperative/motivated patient and a good support system it can work.
In reality there are a LOT of bad methadone clinics that are essentially warehouses for addicts. They dose 'em (maybe a little too heavily) and don’t provide counseling and are willing to string these folks along for years or a lifetime – it’s essentially legalized drug dealing. Some clinics are outright cruel the way they treat people, and make things worse. Yeah, a lot of the bad stories are true, unfortunately.
Where I worked we actually did try to do things the way we were supposed to, but since it was an outpatient clinic there were sharp limits to what we could do. Really, the only folks we could actually help were the self-motivated ones who wanted to quit and were sincerely looking for help to do so. The addicts that were there because the alternative was jail or having their kids taken away… they did just enough and no more to avoid that dreaded alternative. And a lot of folks showed up, stayed for a month or two (or a week or two) and then left. Well, that’s reality. We helped some people. Some got worse. Most were much the same. That’s what happens in drug rehab programs, and it can get very depressing.
Fact is, methadone is going to help only a small percentage of addicts - but that’s true of ANY method you name. If you have a 15-20% long-term success rate you are doing extremely well. 4 out of 5 are just not going to succeed at any given program at any given time. A number of those will succeed if they keep trying - no one method works for everyone.
And yes, pure opiates are not as toxic as people think. They’re not wonderful, they do have side effects, and they can kill you if you OD, but most of the folks we saw had far more medical problems generated from the crap used to dilute the heroin/whatever than from the opiate itself. Among other things - kidney and liver damage were fairly common. Liver damage from hepatitis in needle users, as well as infections of the tissue around the heart, came from less-than-sterile injections (and the diabetic addicts almost never had hep or pericarditits because they could easily obtain clean, sterile syringes) Which is the whole point around needle exchange programs - it’s not to cure addiction, it’s to limit the spread of disease from unsafe needle practices. (It also has the side effect that where needle exchanges take place you will find no used needles on the ground anywhere.)
We also did a study with the pregnant addicts (and, boy, howdy, was that a hot potato!) where we were able to show that 1) the earlier in pregnancy you got an addict into treatment the better than chances of having a healthy child and 2) it really was the street drugs/high-withdrawal cycles that were doing the damage to the kids, not the opiates themselves. When we got the moms into the program in the first trimester and the moms were cooperative (always a big question with addicts) we were seeing full-term births, normal weight kids (though on the low end of normal), and no more problems than with comparable, non-addicted women. Get 'em late in the pregnancy and/or noncompliant you had all sorts of horrible things go wrong.
Working with pregnant addicts is really tough - they generate all sorts of very mixed feelings. And Bad Things can happen to the kids.