New study finds short-term use of opioids implicated in protracted pain
Scientists have found that painkillers such as morphine, oxycodone and methadone could actually prolong and increase pain, even after a few days.
The research, conducted on rats by scientists at the University of Colorado Boulder, US, could have an impact on how people are prescribed the painkillers. Opioid abuse is said to affect up to 36 million people worldwide.
The researchers found that after only a few days of exposure to morphine in rats could result in increased chronic pain for several months. In particular, it led to the rats producing pain signals from immune cells in the spinal cord.
Led by the university’s Assistant Research Professor Peter Grace and Distinguished Professor Linda Watkins of the Department of Psychology and Neuroscience, the scientists observed that damage to the peripheral nerve in a rat results in a message from the injured nerve cells to the supportive glial cells in the spinal cord that protect neurons in the nervous system. The glial cells are sent into panic and are then ready for further impact.
“I look at it like turning up a dimmer switch on the spinal cord,” says Prof Grace.
The scientists then treated the damaged area with opioids for five days with the glial cells still extremely activated and further reactions following such as spinal cord inflammation. The researchers described it as the original pain being the first hit to the system and then the morphine treatment causing a second hit similar to slapping a person’s face which then continues for months.
“You might get away with the first slap, but not the second,” says Prof Watkins. “This one-two hit causes the glial cells to explode into action, making pain neurons go wild.”
The study, which was published in Proceedings of the National Academy of Sciences, found that the combination of the injury followed by treatment with morphine created a landslide of glial cell signalling from the interleukin-1beta, which elevates activity of the pain-responsive nerve cells in the spinal cord and brain.
The scientists also identified a way of shielding the receptors of the glial cells that recognise the opioids. This could help to reduce the chronic pain.
“The implications for people taking opioids like morphine, oxycodone and methadone are great, since we show the short-term decision to take such opioids can have devastating consequences of making pain worse and longer lasting,” says Prof Watkins.
For more in-depth features, interviews and information, subscribe to Arthritis Digest magazine, a popular title that’s published six times a year. Click here for the digital version or tel 0845 643 8470 to order your had copy. You’ll know what your doctor is talking about, what new drugs are in the pipeline and be up to date on helpful products.
