I hope David is paraphrased here, because you never 'shake off' your addiction.
You make a daily choice not to use.
Sometimes, you make an HOURLY choice not to use.
I hope there is a way to remove the physical pain that he still has; maybe there is a medicine that is non-narcotic, some sort of inflammation reducer of some kind, that will help him. Maybe a certain kind of exercise will help. That is the first step. If he really is in excruciating back pain, his active life will be murder for him. Even surgery might be an answer; things change so quickly in the world of medicine. There may be new options now.
But I do realize that the addiction may have started with the pain but then ended as a pure addiction to either the feelings the pills gave him or simply to not have the bad feelings that came when he stopped. At the end, it may have been that at the smallest provocation (before a dinner with friends, or just feeling a little under the weather, etc.) he just reached for that bottle of blues. That will be the tough part -- real life, straight up, as it were.
But Rush, if you are reading this, please realize that you can handle real life, aches and all. You will be able to do it, as hard as it may seem at first. Take your joys from the little things and go with it. Dance with your cat a la my 24/7 screensaver (which my little son calls "Rush throwing up a cat" because it looks like the cat is coming out of your mouth); begin a habit of long ocean swims (or are there sharks?); find comfort in a safe food or drink, like hot tea. You can do this.
And welcome back.
Yeah, kinda like my sex addiction... Nobody was more pleased than Rosie when I successfully beat the habit.