Kicking the PCP habit

Will doctors someday be able to use antibodies to treat drug addicts?

By Dawn MacKeen

Aug 24, 1999 | Greg Hayner doesn't see a lot of PCP addicts these days, but he may in the future. As a pharmacist who has worked at San Francisco's Haight-Ashbury Free Clinic since PCP's heyday in the late '70s and early '80s, he remembers its effects all too clearly -- the superhuman strength, the disassociated thinking, the demonic visions. "People get very paranoid and combative," he says. "They think what they're experiencing is reality and they react like their very lives are dependent on it, so they are liable to hurt themselves or those around them."

Every drug goes in cycles: One generation uses and abuses a drug, learns about its harmful effects and then moves on; 20 years later, the next generation discovers the substance. Now, as was true two decades ago, there's not much Hayner and his colleagues can do to help treat those addicted to phencyclidine (PCP) besides counseling and advising the person to drink a lot of cranberry juice, to flush the drug out of their system.

But the next time PCP comes around, doctors might be ready for it. Researchers at the University of Arkansas for Medical Services (UAMS) have developed a promising new way to treat those addicted to PCP, or "angel dust." In animal studies, one shot of monoclonal antibodies blocked the pleasurable hallucinogenic effects of PCP for two weeks; and researchers estimate that it might work for up to two months in humans. (Monoclonal antibodies are copies of animal antibodies.) "If someone enters into a treatment plan, you might give them a dose of this antibody so that if they slipped during the program and tried to use the drug, they would not get the rewarding effects of it and they may continue with therapy," says Michael Owens, Ph.D., a professor of pharmacology and toxicology at UAMS. "We're hoping to get them through that weak moment, through that difficult period of trying to kick their habit."

Owens presented his findings on Monday at the 1999 American Chemical Society meeting in New Orleans. This technique, which has only been tested on rats thus far, is also promising as a general drug treatment prototype. The antibody, once administered, binds to the drug and neutralizes it, so the body can metabolize it or excrete it. It keeps it from ever reaching the brain or target tissues, which differentiates it from other treatments. "We think it may be a first generation medication for a new approach," Owens says. In the future, he speculates, cocaine or amphetamine addiction might be treatable in this way.

The benefit of using monoclonal antibodies this way is that they work instantaneously; as opposed to antibodies used to make vaccines, which often take weeks to go into effect. Time, Owens says, is crucial in treating drug addicts; since the monoclonal antibodies work so quickly, if the user slips and takes a dose of PCP soon after taking the shot, he will feel few or no effects of the drug. Therapy also should be used in conjunction with the shot. Owens is quick to point out that this treatment does not curb the craving for the drug, but believes that preventing the user from getting high is crucial to getting someone to quit. (He is also the lead researcher on using these antibodies to treat PCP overdose, though that is several years away from making it onto the market -- if it ever does.)

But for Cynthia Kuhn, a professor of pharmacology at Duke University Medical Center, there are two major drawbacks to treating PCP addicts this way: possible side effects, such as anaphylactic shock, which occurs when foreign proteins are introduced into the body; and a user's lack of devotion to just one drug. "For those rare people who only take PCP and you can keep them from getting high from PCP, this might be an effective treatment," says Kuhn, who is the co-author of "Buzzed: The Straight Facts About the Most Used and Abused Drugs." "But in reality, the average drug user is not that loyal; they are promiscuous. Because the antibody is so selective, it's going to prevent the person from reacting to PCP, but cocaine is still going to work fine. And your average drug addict will figure this out very quickly." So if the person keeps switching drugs, she hypothesizes, are they going to give the user five different antibody shots?

To Hayner -- who saw many patients come into the clinic, wanting to get better but so messed up they forgot that they ever came in -- this treatment sounds promising. If it ever gets out of the test lab, he says, someone at his clinic could administer a shot and the addict's high would be blocked for one or two months. "The thing about PCP that always bothered people is we didn't have much of a handle on it," he says. "And this will lend a ray of hope to the whole thing."

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