This gives new meaning to "Discover the Man you never knew"
So many different versions of the same story.
I can only comment based on my real life experiences with drugs.
Many therapeutic drugs, do have side effects. Depending on the dose and type of drug you are talking about.
Analgesics are a class of drugs used to relieve pain. The pain relief induced by analgesics occurs either by blocking pain signals going to the brain or by interfering with the brain's interpretation of the signals, without producing anesthesia or loss of consciousness. There are basically two kinds of analgesics: non-narcotics and narcotics.
I would confidently say, that MJ did need to take some sort of pescription drugs, for arthritis, bought on by either lupus of family history. Therefore, yes he would have been in alot of pain, especially being a dancer. Its only when you start to "make up" your pain, that it becomes a problem. Some cause drowsiness, and some don't .......