Iboga is not the only tool used in the ceremonies. There are other psychological nuances that go on during these 3-5 day cleanses. The Bwiti ritual goes on for days without sleep, or food. Some even dance for super long periods up to 18 hours, drinking only iboga water. This gives the individual the sense of the idea that "everything I need is within me".
Mind you, these are in highly controlled environments, run by EXPERIENCED practitioners. So while it is one tool in the toolbox, Iboga, alone and in itself, is not a miracle cure, as dragonrider said.
But..... if he does the research, and finds somewhere that is safe, with someone who has experience. Then I would say go for it. Just remember that not all is as it seems in the world of shamanism. Not every "shaman" has your best interest in mind, and it is important that shamans are thoroughly vetted.
I hope that you are able to find a way to help him before it is too late. As a recovering heroin addict, myself, I know how difficult it can be for both the addict and the addict's loved ones. Tell your friend not to give up on him, he is still in there somewhere. I can also say that Iboga is not the only helpful psychoactive that can help quell the terrors of addiction. I personally had brief success with LSD. Even willed a full purge which made the withdrawal symptoms almost nothing. This particular event helped me to acheive a little short of a year clean. I currently use kratom or akuamma when I need to take care of any pain, which unfortunately, is a lot due to several injuries from skateboard and motorcycle accidents. I also microdose psilocybe mushrooms once a week, and use 5-meo-dmt on a bi-monthly schedule. The self-awareness created by the 5-meo-dmt and the anxiety and depression treating effects of micro-dosing all in all leaves me with a clarity and a headspace where I no longer feel the need to escape reality every moment of every day. October 31st will be 2 years with no opiates; the longest I have abstained since I began using them.
Best wishes to all involved. This is not an easy road, but it is a conquerable one. There needs to be absolute cohesion between the parties. Support him, but do not enable him. Let him know that you will be there for him, but will not be walked on. And most importantly, the decision needs to be his. He needs to want to do it for himself. To need that clean time in his bones. This requires a lot of self restraint, and work. The homework needs to be done daily. Recognizing past traumas, dealing with them. Finding the root as to why he needed to escape in the first place. He needs to heal the pain. Forgive himself for any wrongdoings first. Only then will the shamanic medicines be of any help to him.
May we continue to be blessed