Opioid painkillers such as morphine may increase Opioid painkillers such as morphine may increase

Opioid Medications May Increase Chronic Pain

A man massages his shoulderOpioid painkillers such as morphine may increase chronic pain, according to a study that looked at the use of opioids to dull pain in rats. The research was published in the Proceedings of the National Academy of Sciences.

Prescription opioids, which are chemically related to the drug heroin, are a leading cause of drug addiction and overdose. Between 1999 and 2014, more than 165,000 people died from prescription opioid overdoses, according to the U.S. Centers for Disease Control and Prevention (CDC). Physicians often prescribe opioids to treat chronic pain, but the CDC argues this practice may contribute to the opioid abuse epidemic—particularly when less addictive options are available.

Do Opioids Make Pain Last Longer?

To assess how opioids alter pain, researchers administered morphine to rats with a pain-causing nerve injury. Initially, morphine greatly reduced apparent pain in the rats. Within five days of treatment, the rats experienced spinal cord inflammation and chronic pain.

According to the study, peripheral nerve injuries in rats send a message to spinal cord glial cells—immune cells that fight infections and attack foreign organisms. When researchers treated the rats with morphine, the glial cells overreacted, producing spinal cord inflammation. This process increases signals from a protein called interleukin-1beta (IL-1b). IL-1b then increases activation of pain-sensing neurons in the brain and spinal cord, prolonging the perception of pain beyond the initial injury.

The study also uncovered a mechanism for blocking glial cell receptors for opioids. This process might still enable pain relief, but prevent chronic pain.

A New Understanding of the Opioid Epidemic

The research only looked at rats, so scientists do not yet know if the same process occurs in humans. Because rats and humans have very similar immune and nervous systems, it is likely that a similar process could occur in people. If that is the case, this research could provide new insights into the opioid abuse epidemic.

Scientists already know opioids tend to work less effectively over time. If this decrease in efficacy is accompanied by an increase in chronic pain, people with chronic pain may steadily increase their use of opioids in an attempt to break free of pain.


  1. CDC guideline for prescribing opioids for chronic pain. (2016, March 16). Retrieved from http://www.cdc.gov/drugoverdose/prescribing/guideline.html
  2. Narcotic painkillers prolong pain, CU-Boulder study finds. (2016, May 27). Retrieved from http://www.colorado.edu/news/news/multimedia/narcotic-painkillers-prolong-pain-cu-boulder-study-finds
  3. Narcotic painkillers prolong pain in rats, says CU-Boulder study. (2016, May 30). Retrieved from http://www.eurekalert.org/pub_releases/2016-05/uoca-npp052416.php
  4. Prescription opioid overdose data. (2016, March 12). Retrieved from http://www.cdc.gov/drugoverdose/data/overdose.html

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  • Martina

    June 3rd, 2016 at 10:29 AM

    Given all of the information in the news today about addiction and how these drugs are ruining so many lives it is curious to read that the thing that these people are actually trying to prevent is still on the rise even with the use of these medications. Could it be that they are just no longer aware of what real pain feels like and so they want to be numb and any amount of hurt will cause them to say that they hurt even more? I am thinking make them more susceptible to the pains that the rest of us could probably just brush away as being pretty minor? This is such a huge problem and I want the medical community to really sit up and pay attention to the damage that is being done to society overall with the continued use of these drugs. I know that some people legitimately need them, but surely not everyone who is taking them.

  • lowery

    June 4th, 2016 at 8:20 AM

    How is this even possible? Don’t they get prescribed because they are pain killers?

  • Maisie

    June 6th, 2016 at 3:18 PM

    I have a sickening feeling that this is a problem that has gotten so out of control that it is going to be next to impossible for the medical and drug treatment communities to get this problem reigned in anytime soon. Every where you look there is a new story about how people are becoming more and more addicted and it seems that doctors have no hesitation to continue writing the prescriptions. There has got to be a real change in the way that pain treatment is managed as well as how we treat those who are already addicted before we start to get a little more control over this very serious issue that we now face as a society.

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