An international team of scientists is claiming a “major breakthrough” in blocking addiction to narcotics, while at the same time increasing pain relief from opioid drugs.
Researchers at the University of Adelaide in Australia and the University of Colorado have discovered a key mechanism in the body’s immune system that amplifies addiction to opioid medications. Their study is being published in the Journal of Neuroscience.
“Our studies have shown conclusively that we can block addiction via the immune system of the brain, without targeting the brain’s wiring,” says lead author Dr. Mark Hutchinson, a research fellow at the University of Adelaide’s School of Medical Sciences. “Both the central nervous system and the immune system play important roles in creating addiction, but our studies have shown we only need to block the immune response in the brain to prevent cravings for opioid drugs.”
The researchers say the drug naloxone can block the immune-addiction response. Naloxone is an opioid inverse agonist that has been used for many years to treat heroin and morphine overdoses by counteracting depression of the brain and respiratory system. When naloxone is combined with the opioid buprenorphine to make suboxone, it is also used to treat opioid addiction.
The research team focused its efforts on the immune receptor known as Toll-Like receptor 4 (TLR4), which acts as an amplifier for addiction. Opioid drugs such as morphine and heroin bind to TLR4 in a way similar to the body’s immune response to bacteria.
“Naloxone automatically shuts down the addiction. It shuts down the need to take opioids, it cuts out behaviors associated with addiction, and the neurochemistry in the brain changes,” said Hutchinson. “Dopamine, which is the chemical important for providing that sense of ‘reward’ from the drug, is no longer produced.”
“This has the potential to lead to major advances in patient and palliative care,” said senior author Linda Watkins, a professor at the Center for Neuroscience at the University of Colorado Boulder, who believes naloxone could be co-formulated with morphine to give patients relief from pain without the risk of addiction.
“This work fundamentally changes what we understand about opioids, reward and addiction. We’ve suspected for some years that TLR4 may be the key to blocking opioid addiction, but now we have the proof,” said Watkins.
The researchers say clinical trials on a new formulation of naloxone based drugs are possible within the next 18 months. Their study was funded by the National Institute on Drug Abuse in the U.S.and the Australian Research Council.