
What if the opioids patients take after surgery lead to chronic pain? That's a question researchers are asking after their study in Anesthesia and Analgesia found that rats given morphine felt pain for 3 weeks longer than rats given no opiates after surgery.
In one experiment, researchers at the University of Colorado Boulder performed laparotomies on rats. They gave half the rats morphine for 7 days postsurgery and half a saline solution. All the rats that received morphine experienced pain — based on their sensitivity to touch — for more than 3 weeks after surgery than the rats that received saline.
Other experiments in which rats were given morphine for 8 days (tapered off for 2 more days) and 10 days (dose abruptly discontinued) showed similar results — the morphine rats felt post-op pain for more than 3 weeks longer, and the longer they received morphine, the longer their pain lasted. Gradual tapering made no difference.
"This indicates that there is another dark side of opiates that many people don't suspect," says senior author Linda Watkins, PhD, a professor in the department of psychology and neuroscience at University of Colorado Boulder. "It shows that trauma, including surgery, in combination with opiates can lead to chronic pain."