Look at Keith Richards. I don't think anyone, including him, can understand why he's still walking around. That guy consumed enough drugs in his lifetime to sink a container vessel. I saw an interview with him, and he contributes it to having his blood changed out several times, over a period of years at a clinic in Switzerland.
It is a very expensive process that is not covered by any insurance, because it is, "experimental". It takes weeks to do because they can't just drain your blood, and refill it, like doing an oil change on your car. It is a gradual process that takes several days, and a LOT of blood. But he feels it saved his liver and kidneys from failure, over so many years of heavy drug use. He said he knew many people he hung around with at that time, who used drugs as much as he did. And they're all gone. Mostly from liver or renal failure.