The painkillers were found to spur a "cascade" of reactions that led to more pain signals being fired from nerve cells in the spinal cord and brain.
"What we found were those rats that were treated with placebo control were recovering about 4 to 5 weeks after that," said researcher Peter Grace. "But those rats that had morphine took twice as long to recover. So, it took about 10 or 11 weeks to return to normal threshold."
Distinguished Professor Linda Watkins said, "This is a very ugly side to opioids that had not been recognized before."
Grace suggests if painkillers work the same way in humans as they do in rats, it could help explain why they're so addictive. Using them could cause more pain, which, in turn, leads people to use them longer, leading to a vicious cycle.
This research could lead to better pain treatments.
Full Article - researchgate.net