From: [C upi] at [clari.net] (UPI)
Newsgroups: clari.biz.industry.health.pharma,clari.news.alcohol+drugs
Subject: Ritalin fails to wean cocaine addicts
Keywords: health, social issues, substance abuse, pharmaceutical
Organization: Copyright 1996 by United Press International
Date: Mon, 16 Sep 1996 14:30:14 PDT
                                         
                          UPI Science News      
        WASHINGTON, Sept. 16 (UPI) -- A brain imaging study has given new  
insight into why some cocaine substitutes intended to help addicts kick 
the habit may actually give a higher high, said researchers Monday. 
        These drugs are designed to bind to a brain mechanism known as the  
dopamine transporter (DAT), which regulates the mood-lifting substance 
dopamine. By binding to the DAT, the drugs in theory should neutralize 
the high from cocaine. 
        But in a new study using brain imaging techniques, investigators  
found that injections of one of these drugs, methylphenidate (MP), 
blocks only about eight tenths of the DAT, which is not enough to have a 
therapeutic effect. 
        Methylphenidate is the scientific name for the controversial drug  
Ritalin, which, in its oral form, is used to treat attention-deficit 
disorder (ADD) in children. 
        ``Clearly, without any interpretation or anything, these strategies  
are not going to work unless a very significant amount of the 
transporter is occupied,'' said Nora D. Volkow, chairman of the medical 
department and director of nuclear medicine at Brookhaven National 
Laboratory, in Upton, N.Y. 
        MP would have to be administered at dangerously high doses to work in  
treating cocaine, said Volkow. She led the team of researchers whose 
work on cocaine and Ritalin appears in the Proceedings of the National 
Academy of Sciences. High doses of drugs that bind to DAT could also 
damage the heart and cause seizures, she said. 
        ``Based on our results, I don't think we will ever be able to use  
methylphenidate to treat cocaine abusers,'' said Volkow. 
        In previous studies, addiction researchers tried but failed to wean  
cocaine abusers with DAT binding drugs, she said. Volkow believes that 
the drugs might have worked, but only at the higher, possibly toxic, 
doses. 
        ``They were giving doses, based on our results, that are not going to  
be effective,'' she said. ``In fact, what we are postulating is: by 
giving them, they are going to make cocaine more efficient.'' 
        In the study, eight men between the ages of 25 and 35 with no history  
of drug abuse, were given two injections of MP, spaced one hour apart, 
about the time it would take for the high from the first dose to 
subside. 
        The second dose produced a high similar to the first, even though 80  
percent of the drug remained in the brains. The researchers found that 
``in contrast to the predictions of the 'cocaine substitute' concept, in 
this study we were unable to block the high by prior DAT blockade.'' 
        Some of the subjects also reported feeling no high after either dose,  
despite high levels of MP in their brains. This suggests that DAT 
occupancy alone is not enough to explain the cocaine high. 
        The researchers also said: ``Inducing partial occupancy of DAT with a  
'therapeutic' medication might even enhance the high experienced after 
self-administration of cocaine.'' The use of MP to treat cocaine abusers 
actually increased cocaine craving and consumption in earlier studies. 
        Researchers estimate about 2 million Americans are addicted to  
cocaine. Many laboratories are seeking a solution, including vaccines, 
cocaine analogs and drugs that interfere with the three major brain 
mechanisms that come into play in cocaine abuse, said Dr. Herbert 
Kleber, a professor of psychiatry at New York City's Columbia University 
Medical School. 
        At first, scientists thought that they would be able to use MP in the  
same way methadone is used to treat heroine addiction, he said. But in 
Kleber's own experiments using MP to treat cocaine addiction about ten 
years ago, he found the drug ineffective. 
        Volkow's research, Kleber said, ``provides a rationale for why our  
studies didn't work.'' 
        He is, however, now testing the drug in one group of patients,  
cocaine addicts who also have attention-deficit disorder. He estimates 
about 15 percent to 20 percent of people hooked on cocaine have ADD. 
 (Written from New York by Mara Bovsun)