It's complicated. There are performers who are known to use both an opiate and an upper before going on stage. There are people who use both for long periods, and have their use down to a science. After a respite in opiate use, many people who are addicts report a rush or burst of energy right after using again. This is sought after.
Many of us would not have that response. Some of us have opiates (prescribed) that we never used. There are likely genes involved in this, because other people are so into opiates that they steal people's prescriptions. I know doctors, nurses, lawyers, judges, police, sheriffs, professors and many others who have used opiates because of perceived benefits. The blurb below is about heroin, but contains a statement about oxycodone.
Heroin is a highly addictive opioid drug, and its use has repercussions that extend far beyond the individual user. The medical and social consequences of drug use—such as hepatitis, HIV/AIDS, fetal effects, crime, violence, and disruptions in family, workplace, and educational environments—have...
nida.nih.gov
From that page:
A little too much, though, and the person may get drowsy (the "nods"). So they often use more than one drug for the exact effect they are seeking (polypharmacy).
View attachment 404076
That's from this site:
OxyContin is a long-acting formulation of the drug oxycodone, which is an opioid used to treat pain. Taking too much can cause a high and lead to abuse.
www.therecoveryvillage.com
Which also explains that people who use the same drug for pain do not get this feeling. It's what the addict feels. It also explains how the addict processes their pills so as to get around the built-in time release (which doesn't allow much of a high).
"Feel more happy." "Less discouraged." "Things...more pleasing."
For some people, that would certainly feel like a fire in the belly, a kind of invincibility. However, I believe that it's highly likely AM was self-medicating for other symptoms (not physical pain - but perhaps psychic pain).
IMO.