Scientists have developed a new vaccine that blocks the pain-numbing effects of the opioid drugs and decreases the risk of fatal overdose, a growing cause of death in the US.
The vaccine takes advantage of the immune system's ability to recognise, seek out and neutralise invaders.
"We saw both blunting of the drug's effects and, remarkably, prevention of drug lethality," said Kim D Janda, professor at The Scripps Research Institute (TSRI) in the US.
"The protection against overdose death was unforeseen but clearly of enormous potential clinical benefit," Dr Janda said.
Opioids were designed to reach receptors in the brain, causing pain reduction and feelings of euphoria.
For their vaccine, the researchers combined a signature opioid structure with a molecule to trigger an immune response. When injected, the vaccine teaches the immune system to bind to the drug molecule and remove it from circulation.
The vaccine-derived antibodies were tailored by scientists to seek out the prescription drug and block the opioid from reaching the brain, potentially depriving a person of the "reward" of consuming the drug, Dr Janda said.
The scientists believe a vaccine approach could have an advantage over current opioid addiction therapies because it would not alter brain chemistry like many of today's anti-addiction therapies do.
"The vaccine approach stops the drug before it even gets to the brain. It's like a preemptive strike," said Cody J Wenthur, a research associate in the Janda laboratory.
The researchers found that their vaccine design blocked pain perception of oxycodone (oxy) and hydrocodone (hydro) use in mice.
Indeed, those given the vaccine did not display the usual symptoms of a drug high, such as ignoring pain and discomfort. In further tests, the rodents also appeared less susceptible to fatal overdose.
Although it was found that some vaccinated mice did succumb to the opioid drug's toxic effects, the researchers noted that it took much longer for the drug to impart its toxicity.
If this effect holds true in humans, the vaccine could extend the window of time for clinical assistance if overdose occurs.
The scientists also discovered that the vaccine remained effective in mice for the entire 60-day study period, and they believe it has the potential to last even longer.
"Our goal was to create a vaccine that mirrored the drug's natural structure. Clearly this tactic provided a broadly useful opioid deterrent," said Atsushi Kimishima, a research associate in the Janda laboratory.
The study was published in the journal ACS Chemical Biology.
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