It's important to start off by noting that the opioid study everyone's buzzing about this Tuesday morning was conducted on animals and not humans. The research by Colorado University's Peter Grace and Linda Watkins looked at injured rats that were given morphine and came to a startling conclusion: that even a short treatment with the opioid appeared to prolong the duration of pain for months.
The work, published in the Proceedings of the National Academy of Sciences (PNAS), involved looking at pain from only one specific issue — damage to the central or peripheral nervous systems. In people, this can lead to feelings of burning and shock and a wide variety of other kinds of discomfort. This kind of pain was stimulated in rats by pinching the sciatic nerve in their legs. One group was given nothing while the other got morphine for five days. To measure their level of pain, the researchers stimulated their paws by pinching to see how they reacted.
Those in the first group with no morphine, appeared to bounce back in four to five weeks. But the ones who were treated with morphine appeared to be in pain for 10 to 11 weeks.
Scientists have known for more than three decades that nerve injuries intensify the release of pain signals. Grace and Watkins believe that opioids might do the same — putting the cells into a kind of "overdrive." Grace explained that the body may be "recognizing opioids as something that’s foreign and needs to be eliminated and so it’s triggering this immune response causing the release of these pain molecules that are then increasing the perception of pain in the brain.”
Previous work has shown morphine tends to work well at first but that its effectiveness appears to decrease over time. The new work raises questions about whether this decrease in effectiveness may have been misinterpreted and that at some point morphine switches from alleviating pain to inducing it.
Grace, an assistant research professor in the university's department of psychology and neuroscience, said that there are ways to get around this issue with other drugs that can counteract the response.
"So you can still take your opioids but if you block this immune response that’s occurring at the same time, then you can still get that pain relief but you can prevent these long-term consequences from occurring," Grace said.
The question of what exactly opioids do to our bodies is critically important as the United States is grappling with a record number of overdose deaths from the painkillers. The government has been urging doctors to use more caution when prescribing the highly addictive painkillers, and the Food and Drug Administration earlier this year began to require new "black box" warnings on packages that warn of the risk of addiction, abuse, overdose and death.
FDA Commissioner Robert Califf called the issue one of the most "urgent and devastating public health crises facing our nation."
As everyone knows, experimental results in rats don't always translate to the same results in humans, but the study in the PNAS raises yet another red flag about opioids that should give people pause when weighing whether to take them.