I have heard that he was in chronic pain from an accident. When he did a show here he would have to be driven to the stage on a golf cart, then get onstage and perform and then get driven back. He did have a drug problem in the past which makes one wonder why his Doc would write scripts for massive amounts of pain meds?
That’s the way opioids work; you need more and more to get the same pain relief. However, the list includes benzodiazepines [temazepam (Restoril), alprazolam (Xanax] possibly for anxiety, sleep, muscle relaxation, etc and an anti-depressant, citalopram (Celexa). Looks like an addict, possibly with underlying chronic pain as the initiating factor.