An international team of scientists has succeeded in blocking morphine and heroin addiction, while at the same time increasing pain relief.
They say they've discovered the key mechanism in the body's immune system that amplifies addiction to opioid drugs, and that laboratory studies have shown that the drug (+)-naloxone will selectively block the immune-addiction response.
The results could lead to new, non-addictive pain-relief drugs, as well as helping heroin users to kick the habit, they say.
"Our studies have shown conclusively that we can block addiction via the immune system of the brain, without targeting the brain's wiring," says Dr Mark Hutchinson of 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 team has focused its research efforts on the immune receptor known as Toll-Like receptor 4 (TLR4).
"Opioid drugs such as morphine and heroin bind to TLR4 in a similar way to the normal immune response to bacteria. The problem is that TLR4 then acts as an amplifier for addiction," says Hutchinson.
"The drug (+)-naloxone automatically shuts down the addiction. It shuts down the need to take opioids, it cuts out behaviours associated with addiction, and the neurochemistry in the brain changes – dopamine, which is the chemical important for providing that sense of 'reward' from the drug, is no longer produced."
The researchers say clinical trials may be possible within the next 18 months.