UCLA: A new study by UCLA researchers has found that Naltrexone, a drug used
to treat alcoholism, may also be a promising treatment for addiction to
methamphetamine. “The results were about as good as you could hope for,” said Lara
Ray, a UCLA associate professor of psychology, director of the UCLA
Addictions Laboratory and lead author of the new study. The study, published in the journal Neuropsychopharmacology, was the
first in the U.S. to evaluate Naltrexone for treating methamphetamine
addiction.
Researchers analyzed 22 men and eight women who use
methamphetamine an average of three to four days a week.
During a four-day hospital stay, each person was each given either
Naltrexone — 25 milligrams the first two days, 50 milligrams on days
three and four — or a placebo daily. Ten days later, the subjects were
readmitted to the hospital for four more days; those who had taken
Naltrexone earlier were given placebos, and vice versa.
On the last day of each hospital visit, all participants were given
intravenous doses of methamphetamine. Three hours later, the researchers
asked how they felt and how much they wanted more of the drug.
The scientists found that Naltrexone significantly reduced the
subjects’ craving for methamphetamine, and that it made them less
aroused by methamphetamine: Subjects’ heart rates and pulse readings
both were significantly higher when they were given the placebo than
when they took Naltrexone. In addition, participants taking Naltrexone
had lower heart rates and pulses when they were presented with their
drug paraphernalia than those who were given placebos.
Ray said the results indicated that Naltrexone reduced the rewarding
effects of the drug — those taking Naltrexone did not find
methamphetamine to be as pleasurable and were much less likely to want
more of it.
Naltrexone was well tolerated and had very minimal side effects. The
researchers found that men and women both were helped by taking
Naltrexone, although the positive effect on men was slightly smaller. It
made no difference whether the participants were given Naltrexone
during their first hospital stay or their second.
Naltrexone works by blocking opioid receptors in the brain. Ray said
that in previous studies, people undergoing treatment for alcoholism
reported getting less of a “high” from drinking when they take
Naltrexone.
Ray, whose research team studies the causes of drug and alcohol
addiction and possible treatments, plans to examine whether Naltrexone
would be more effective in combination with other pharmaceuticals and at
different doses. Her research is funded by the National Institute on
Drug Abuse and UCLA’s Clinical and Translational Science Institute.
Twenty-five of the participants also underwent functional magnetic
resonance imaging, or fMRI, brain scans in UCLA’s Center for Cognitive
Neuroscience. Ray and UCLA graduate student Kelly Courtney, a co-author
of the Neuropsychoparmacology paper, are analyzing that data.
Methamphetamine use disorder is a serious psychiatric condition that
can cause psychosis and brain damage, and for which no FDA-approved
medication exists. An estimated 12 million Americans have used
methamphetamine, nearly 400,000 of whom are addicted to it, according to
recent estimates.
Although the new study is promising, it needs to be backed up by
clinical trials, said Ray, who is also a member of the UCLA Brain
Research Institute. The next step in evaluating Naltrexone’s
effectiveness for treating people addicted to methamphetamine is already
underway: the National Institute on Drug Abuse is sponsoring clinical
trials.