UCSF researchers have discovered a pain relief strategy that could provide a long-sought alternative to morphine, without the drug's addictive quality. The finding, the latest in a series of revelations regarding a class of drugs known as kappa-opioids, illuminates just how intricately wired and discriminating the human brain is.
Kappa-opioids have been clinically available for 40 years, but have long been dismissed as ineffective pain killers. Published studies have suggested that women prefer kappa-opioids to morphine during labor and delivery, but current clinical wisdom dictates that they are ineffective, and the pharmaceutical industry's assessment of their effectiveness has been lukewarm at best.
During the last five years, UCSF researchers have revealed a more complex picture of the drug. Their findings have hinted that the drug's full potential has not been tapped. The findings have also provided a window into the complex way in which opioids, including kappa-opioids, act on the pain-modulating circuitry in the body. And these discoveries, in turn, have provided insights into the way men and women experience pain.
In their new study, published in the June 9 issue of Journal of Pain, the researchers appear to have discovered a way to tap kappa-opioid's full potential -- in men and women.
"The potential implications of this finding are really incredible," says the senior author of the study, Jon Levine, MD, PhD, UCSF professor of Oral and Maxillofacial Surgery and Medicine and director of the NIH Pain Center at UCSF. Morphine is the painkiller most often used for severe pain, but it can have limitations -- over time, people can develop tolerance to the drug and/or become dependent on it, and the drug can cause severe constipation.
Low to moderate doses of kappa-opioids, by contrast, have minimal addictive effects. Tolerance is only a minimal problem, and the drugs do not cause constipation.