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Naltrexone May Be Beneficial in Treating Amphetamine Dependence: Presented at SFN

By Glynn Wilson

NEW ORLEANS, LA -- November 20, 2003 -- Naltrexone may potentially decrease the reinforcing effects of amphetamine, and therefore may be used as a treatment for the growing problem of amphetamine dependence. Preliminary evidence from 2 studies reporting results on the subject was presented here November 9^th at the Society for Neuroscience 33^rd Annual Meeting.

According to the United Nations, there are an estimated 29 million amphetamine addicts around the globe, making it the third most addictive substance behind alcohol and cannabis.

"The potential of naltrexone as an adjunct pharmaceutical for the treatment of amphetamine abuse and dependence is promising," said lead author Nitya Jayaram Lindström, MA, graduate student, Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden.

In an open label study "Compliance and tolerability of naltrexone in amphetamine dependent persons", 20 amphetamine dependent patients were treated with naltrexone over a period of 12 weeks. No toxic effects from the drug were found, although side effects included mild nausea and gastronomical distress. The results indicated that naltrexone was well tolerated in this population and adequate compliance was achieved.

The next study was a randomized, double blind placebo-controlled study, comprising of 5 male and 7 female healthy subjects between the ages of 21 and 35. Only subjects with no diagnosis of psychiatric or substance dependence in self or family were recruited reported. They were treated with 4 combinations of naltrexone, amphetamine and placebo at 4 time periods.

A series of subjective, behavioral and physiological tests were conducted during each session. Pre-treatment with naltrexone significantly reduced the subjective effects ("high") of amphetamine in this sample of healthy volunteers, especially over time (i.e. 3 hours). Volunteers in the trial reported that naltrexone reduced the euphoric effects of amphetamine, according to Dr. Lindström.

While the mechanism by which naltrexone modulates the subjective effects of amphetamine are not clear, the authors report, "a possible explanation could be that naltrexone attenuates the direct subjective or mood-altering effects of the drug." The opiate antagonist naltrexone may reduce amphetamine reward by blocking the opiate receptors on the mesolimbic dopamine neurons, interfering with amphetamine-stimulated release of dopamine.

The results of the 2 studies points to the potential of Naltrexone as an adjunct pharmaceutical for the treatment of amphetamine abuse or dependence and according to the authors this merits further investigation.


[Study Title: Effect of Naltrexone on the Subjective Response to Amphetamine in Healthy Volunteers. Abstract 135.5]

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