Morphine can more than double the duration of pain and increase its severity, says a new study. "Our results suggest that treatment with opioids such as morphine may in fact be a contributor to people's chronic pain," says study author Dr Peter Grace from the University of Colorado Boulder and the University of Adelaide.
The study, published in the journal proceedings of the National Academy of Sciences, found that rats with chronic nerve pain treated with morphine for five days experienced prolonged pain sensitivity.
Researchers also said that they discovered how to switch off the pain-amplifying mechanism which would enable morphine's painkilling benefits to be delivered without the drawbacks.
This lasted for up to two-to-three months, more than double that experienced in the control group. "What we found is that the opioid painkiller activates spinal immune cells, causing a further inflammatory response," said Dr Grace.
Dr Grace says the results are of concern because of the huge number of opioid prescriptions being written for patients each year. "The pain is effectively transitioned to a chronic state, making the pain itself both more severe and longer lasting," He added.