Calling them painkillers is almost a misnomer. They don’t actually relieve the pain so much as they affect the way the brain perceives pain, and their extended use can result in the distortion of the brain’s pain/pleasure responses.
“It’s not just about the drug itself, but it actually alters the way they relate to themselves,” Levenson said. “The way they relate to their community and the way they relate to their higher power.”
Combine that reality with the fact that most opiate addicts develop tolerance — requiring a higher dosage to get the same effect — and it is particularly dangerous. An opiate addict is not only responding to a physical craving for the drug, but acting with a skewed brain chemistry.
Source: The Seattle Times – April 7, 2012