How awful. The trouble with some of the most effective pain killers is that they're highly addictive, and in the long run may be worse than some excruciating pain. I've got an elderly relative who's permanently strung out on Oxycontin for hip and back pain, and there's no chance of ever getting her off it. But she's in her 80s and way past trying to do anything productive. In Jackson's case, I wouldn't be surprised if he's been using that kind of stuff for a long time. It would go a long way in explaining his frail-looking condition, while only in his 40s and with no specific medical problems reported other than vitiligo.
My #2 sis was concerned that I'd get addicted to the drugs because I was taking what the orthopedic surgeon had prescribed, so I asked the doc about it. The said that I was taking them for the very real pain I have--and, 6 months from now when I didn't have pain, he'd get concerned.