If these vaccines fulfill their promise, they could revolutionize emergency treatment for PCP and amphetamines. And though they won't cure addiction, they could also help people who want to kick the habit, researchers say.
"Our goal would be to protect against the sudden unexpected urge to use, so that if the patient used it, he wouldn't get the effects," said Dr. Michael Owen, a pharmacologist at the University of Arkansas for Medical Sciences who hopes to begin tests this year on a PCP overdose treatment.
The illegal drugs all have molecules so tiny they sneak unnoticed through the body's immune system. To create antibodies, researchers must hook the molecule to a protein big enough to set off the immune system's alarms.
The drug-plus-protein can be injected directly, to prompt the body to make its own antibodies. Or scientists can create the antibodies by working with laboratory animals and inject them into patients.
Either way, the antibody grabs the drug in the bloodstream, before it gets to the brain.
At least, that's how it works in animals so far.
Antibodies could be used to treat an overdose or block a drug's effects for a longer period, perhaps a month or more.
Both PCP and methamphetamine last for days in the body, unlike cocaine, which is metabolized in 20 minutes or so.
PCP intoxication can be fatal, and both it and amphetamine psychosis can leave permanent mental scars, said Frank Vocci, head of medications development for the National Institute on Drug Abuse and Alcoholism.
The ability to bind the drugs to antibodies could be a major leap forward in treating them, he said.
Cocaine addiction is a much bigger and trickier problem. More than 2 million people need treatment. About 900,000 a year start treatment, but at least three-quarters go back to the drug, Vocci said.
"Maybe if we had something to help them out for the initial period, it might boost the efficacy keep them in longer," he said.
Scientists involved in the research discussed their work Monday at a meeting of American Chemical Association in New Orleans.
Already, one cocaine vaccine, developed by a biomedical company in Massachusetts, is being tried on people at a Connecticut clinic. So far, only the safety has been tested, and it had virtually no side effects, said Dr. Thomas Kosten, a psychiatry professor at Yale University and chief of psychiatry for the Veterans Administration in Connecticut.
The study was not designed to look at the effectiveness of the vaccine, but a few of the participants reported that cocaine "doesn't seem to have the bang that it used to have," Kosten said.