A vaccine that could be used to treat methamphetamine addicts has been developed by scientists in California.
Researchers at The Scripps Research Institute (TSRI) have tested the vaccine on rats, which showed none of the typical signs of meth intoxication after being given the highly addictive drug.
If the vaccine proves effective in humans, it could be the first treatment for meth addiction and give hope for 25 million addicts worldwide.
Michael Taffe, an associate professor in TSRI's addiction science group, said: "This is an early-stage study but its results are comparable to those for other drug vaccines that have then gone to clinical trials."
Methamphetamine, or meth, is one of the most commonly abused drugs in the world.
In the UK, meth is a Class A drug. Its effects cause users to feel exhilarated, alert and awake. But it also leads to paranoia, agitation, confusion and aggression. It is addictive and can lead to a strong psychological and physical dependence.
TV's Breaking Bad, a comedy drama about a chemistry teacher who manufactures the drug to fund his cancer treament, highlights the potentially devastating effects on users.
Over the last few years, scientists have taken a new approach in developing vaccines against drugs. The vaccines evoke antibody responses, meaning they take hold of the drug molecules and prevent them from entering the brain - effectively stopping the user from getting high.
Tests on mice showed that one of the trial vaccines blocked two effects of meth: an increase in physical activity and loss of ability to regulate body temperature.
Michelle Miller, research associate, said: "These are encouraging results that we'd like to follow up with further animal tests and, we hope, with clinical tests in humans."
Chemistry professor Kim Janda added: "This vaccine has all the right features to allow it to move forward in development. It certainly works better than the other active vaccines for meth that have been reported so far."
If the vaccine were developed for addicts, it would be a cost-effective option for addiction treatment as it would be cheap to make and administer, said the scientists. However, they said they needed to find a way to keep the antibody response.
Taffe said: "Extending the duration of protection is the next big scientific challenge in this field."