Potential Medication Can Reduce Effects of Smoked Marijuana in Humans

Apr 12, 2001, 01:00 ET from National Institute on Drug Abuse

    WASHINGTON, April 12 /PRNewswire/ -- Scientists at the National Institute
 on Drug Abuse's (NIDA) Intramural Research Program in Baltimore, MD, have
 confirmed for the first time in humans that chemically blocking the body's
 cannabinoid receptors can significantly reduce the effects of smoked
 marijuana.  The study appears in the April 14th issue of the Archives of
 General Psychiatry.
     Cannabinoid receptors -- proteins on the surface of brain cells -- are
 most dense in brain regions involved in thinking and memory, attention and
 control of movement.  Their exact role in humans is not well understood, but
 animal studies have shown that cannabinoid receptor agonists -- compounds that
 activate the receptor sites -- impair learning and memory and increase
 appetite and food intake.  Previous studies in animals have shown that the
 major effects of tetrahydrocannabinol (THC), the primary psychoactive compound
 in marijuana, are due to its binding to specific cannabinoid receptors located
 on the surface of brain cells.  These effects appear to be lessened when
 cannabinoid receptors are blocked by an antagonist.
     "This research helps point the way toward possible treatment for those
 addicted to marijuana and perhaps may be useful in finding effective
 treatments for other disorders related to the cannabinoid system," says NIDA
 director Dr. Alan I. Leshner.
     In the study, Dr. Marilyn Huestis and her NIDA colleagues used a
 cannabinoid receptor antagonist -- a compound that binds to the receptor and
 blocks agonist compounds from activating it.  The antagonist, SR141716, was
 discovered by Sanofi-Synthelabo of Paris, France, and was used in this study
 with NIDA under a Cooperative Research and Development Agreement (CRADA).
     Participants in the study were given either SR141716 or a placebo and two
 hours later smoked one marijuana cigarette.  Those who received SR141716
 showed significantly reduced marijuana effects, while those who received the
 placebo showed typical marijuana intoxication.
     The results of the study are an important step in understanding the
 complex role of the cannabinoid receptor system in the human brain.
     "Our findings of a significant blockade of marijuana's effects after
 treatment with SR141716, which is highly selective for the CB1-cannabinoid
 receptor sites, demonstrates for the first time in humans that these receptors
 play a major role in mediating the effects of marijuana," Dr. Huestis says.
     In their investigation of the role of the cannabinoid system in humans,
 Dr. Huestis and her colleagues gave increasing doses of SR141716 or placebo to
 63 adult men with histories of marijuana use.  When individuals received
 SR141716 before smoking marijuana, there was a dose-dependent reduction in
 psychological and physical effects of marijuana.  At the highest dose of
 SR141716 (90 mg), volunteers reported a 43% reduction in how "high" they felt,
 a 38% reduction in how "stoned" they were, and a 43% reduction in "drug
 effect" as compared to those who received active marijuana and no antagonist.
 In addition, they had a 59% less increase in heart rate, one of the primary
 physical effects of marijuana.
 
     The National Institute on Drug Abuse is a component of the National
 Institutes of Health, U.S. Department of Health and Human Services.  NIDA
 supports more than 85 percent of the world's research on the health aspects of
 drug abuse and addiction.  The Institute carries out a large variety of
 programs to ensure the rapid dissemination of research information and its
 implementation in policy and practice.  Fact sheets on the health effects of
 drugs of abuse and other topics can be ordered free of charge in English and
 Spanish by calling NIDA Infofax at 888-NIH-NIDA (644-6432) or 888-TTY-NIDA
 (889-6432) for the deaf.  These fact sheets and further information on NIDA
 research and other activities can be found on the NIDA home page at
 http://www.drugabuse.gov .
 
 

SOURCE National Institute on Drug Abuse
    WASHINGTON, April 12 /PRNewswire/ -- Scientists at the National Institute
 on Drug Abuse's (NIDA) Intramural Research Program in Baltimore, MD, have
 confirmed for the first time in humans that chemically blocking the body's
 cannabinoid receptors can significantly reduce the effects of smoked
 marijuana.  The study appears in the April 14th issue of the Archives of
 General Psychiatry.
     Cannabinoid receptors -- proteins on the surface of brain cells -- are
 most dense in brain regions involved in thinking and memory, attention and
 control of movement.  Their exact role in humans is not well understood, but
 animal studies have shown that cannabinoid receptor agonists -- compounds that
 activate the receptor sites -- impair learning and memory and increase
 appetite and food intake.  Previous studies in animals have shown that the
 major effects of tetrahydrocannabinol (THC), the primary psychoactive compound
 in marijuana, are due to its binding to specific cannabinoid receptors located
 on the surface of brain cells.  These effects appear to be lessened when
 cannabinoid receptors are blocked by an antagonist.
     "This research helps point the way toward possible treatment for those
 addicted to marijuana and perhaps may be useful in finding effective
 treatments for other disorders related to the cannabinoid system," says NIDA
 director Dr. Alan I. Leshner.
     In the study, Dr. Marilyn Huestis and her NIDA colleagues used a
 cannabinoid receptor antagonist -- a compound that binds to the receptor and
 blocks agonist compounds from activating it.  The antagonist, SR141716, was
 discovered by Sanofi-Synthelabo of Paris, France, and was used in this study
 with NIDA under a Cooperative Research and Development Agreement (CRADA).
     Participants in the study were given either SR141716 or a placebo and two
 hours later smoked one marijuana cigarette.  Those who received SR141716
 showed significantly reduced marijuana effects, while those who received the
 placebo showed typical marijuana intoxication.
     The results of the study are an important step in understanding the
 complex role of the cannabinoid receptor system in the human brain.
     "Our findings of a significant blockade of marijuana's effects after
 treatment with SR141716, which is highly selective for the CB1-cannabinoid
 receptor sites, demonstrates for the first time in humans that these receptors
 play a major role in mediating the effects of marijuana," Dr. Huestis says.
     In their investigation of the role of the cannabinoid system in humans,
 Dr. Huestis and her colleagues gave increasing doses of SR141716 or placebo to
 63 adult men with histories of marijuana use.  When individuals received
 SR141716 before smoking marijuana, there was a dose-dependent reduction in
 psychological and physical effects of marijuana.  At the highest dose of
 SR141716 (90 mg), volunteers reported a 43% reduction in how "high" they felt,
 a 38% reduction in how "stoned" they were, and a 43% reduction in "drug
 effect" as compared to those who received active marijuana and no antagonist.
 In addition, they had a 59% less increase in heart rate, one of the primary
 physical effects of marijuana.
 
     The National Institute on Drug Abuse is a component of the National
 Institutes of Health, U.S. Department of Health and Human Services.  NIDA
 supports more than 85 percent of the world's research on the health aspects of
 drug abuse and addiction.  The Institute carries out a large variety of
 programs to ensure the rapid dissemination of research information and its
 implementation in policy and practice.  Fact sheets on the health effects of
 drugs of abuse and other topics can be ordered free of charge in English and
 Spanish by calling NIDA Infofax at 888-NIH-NIDA (644-6432) or 888-TTY-NIDA
 (889-6432) for the deaf.  These fact sheets and further information on NIDA
 research and other activities can be found on the NIDA home page at
 http://www.drugabuse.gov .
 
 SOURCE  National Institute on Drug Abuse