Researchers in the U.S. say they're working on a vaccine to prevent meth addicts from getting high

Researchers in the U.S. say they're working on a vaccine to prevent meth addicts from getting high — and the early test results are promising.

Scientists at the Scripps Research Institute in California successfully tested the methamphetamine vaccine on rats. When given meth, the vaccinated critters showed few signs of intoxication.

"This is an early-stage study, but its results are comparable to those for other drug vaccines that have then gone to clinical trials," said senior study author Michael A. Taff, an addiction sciences expert at the Scripps Institute.

Drug vaccines are a burgeoning new field of research. Just like regular vaccines evoke antibody responses against viruses and bacteria, drug vaccines evoke antibody responses against drug molecules.

The idea is to keep those molecules from getting into the brain. That way, addicts don't get high when they use. If they don't get high, they have no incentive to keep using.

Nicotine and cocaine vaccines are already in clinical trials. Meth vaccines have been tested on animals before, but this is the first one to show encouraging results.

That's because a meth high is a more difficult high to block. The meth molecule is so structurally simple it can go unnoticed by the immune system. And once meth is in the system, it stays there for a long time.

"The simple structure and long half-life of this drug make it a particularly difficult vaccine target," Kim Janda, a chemist with the institute, said.

Janda's team developed six vaccines and tested them all until they found the most effective one — MH6. When given meth, the rats vaccinated with MH6 kept the drug mostly in the bloodstream and not the nervous system.

But more work needs to be done to perfect the vaccine, the researchers say.

"I think that this vaccine has all the right features to allow it to move forward in development," Janda said. "It certainly works better than the other active vaccines for meth that have been reported so far."

The researchers say the next step is to tweak the vaccine so it lasts longer. Vaccinating meth addicts every few weeks wouldn't work, they say. Many would fall off the wagon between treatments.

What's more, meth addicts tend to have little money and no health insurance. They're likely to get their treatment from government health services. Weekly or monthly doses would be too expensive a program to maintain.

"Extending the duration of protection is the next big scientific challenge in this field," Taffe said.

The results of the study were published in the journal Biological Psychiatry.