Amphetamines affect men more than women

· It was reported on the 8th of April 2006 [1] that scientists in the US had found that the effects amphetamine upon the brain varied by gender. 
· The article was based on a study conducted by the John Hopkins School of Medicine in Maryland and based on sample of 48 individuals, ranging in age from 18 to 29 years.  28 of the group were male and 15 female. 
· The study will be published in The Journal of Biological Psychiatry on July 1st 2006.
· The article reports that men’s brains showed evidence of up to three times the amount of chemical dopamine as women’s when exposed to amphetamines.  Dopamine is an important neurotransmitter (chemical in the brain) responsible, amongst other things, for feelings of, and anticipation of pleasurable experience)
· The authors claim that this is a discovery that could lead to tailored treatments for drug abuse and neurological diseases.

Title, Authors and Source

Wand G, Munro C, McCaul M, Wong D, Oswald L, Zhou Y, Brasic J, Kuwabara H, Kumar A, Alexander M and Ye W (2006). (Title not yet confirmed) Journal of Biological Psychiatry (To be published 01/07/06).

What were the study objectives?

The main objective of the study was to investigate dopamine release in an area of the brain called the striatal region.  Previous studies in this area had shown that amphetamine-stimulated dopamine release in the striatum differed in male and female mice, however no studies had confirmed gender differences in dopamine release in human subjects.

What was the nature of the evidence?

                                                                   
All potential research participants undertook an assessment of overall health and fitness prior to the study.  The medical checks also covered drug and alcohol use and psychological screening to ensure candidates suitability. 43 individuals were deemed appropriate for the study; this included 28 men and 15 women.
Researchers measured levels of amphetamine-stimulated dopamine by injecting participants with Raclopide C11, which is an anitpsychotic drug that not only binds to dopamine receptor sites but also relinquishes these sites if available dopamine is present.  Raclopride carries a radioactive tag, C11, which can be read using a positron emission tomography (PET) scan. 

Participants were firstly scanned with a dose of Raclopride C11 to measure the number of dopamine receptors for both males and females without amphetamines in the bloodstream, and then participants were administered amphetamines with the same amount of Raclopride C11 and a second scan was conducted.  Results from both scans were then compared for all participants with a particular focus upon differences in dopamine levels between males and females.

Participants were also interviewed to report their experiences, including positive effects (good effect, desire for the drug, high, rush and liking) and negative effects (dizziness, anxiety, fidgetiness, dry mouth and distrust).

What interventions were examined in the research?

No interventions were examined.

What were the findings?

The first PET scan revealed an equal number of dopamine receptors for both males and females in the study group.
In the second scan where amphetamines had been administered alongside Raclopride C11, results showed a higher level of dopamine release for men than for women.
Subjective responses for males were significantly higher in all but one category, dizziness.  In the self reported dizziness category, women rated higher.

What were the conclusions?

Amphetamines have a greater effect on men’s brains than women’s.  The neurotransmitter dopamine was reported to have been three times higher in the brains of men who had been administered amphetamines compared with women. 

How reliable are the conclusions?

· The small sample size (48 individuals) and unequal gender balance within the sample (28 men and 15 women) would suggest the need for further research on this topic to substantiate the gender based claims made by the authors.
· It is difficult to comment fully on the reliability of the study as the full report; including detailed methodology has not yet been published.

References

1. Guardian Unlimited (online) Amphetamines affect women more than men, http://www.guardian.co.uk/drugs/0,,178206,00.html accessed 20/04/06.

Hopkins- led clinical study shoes brain’s reaction to ‘uppers’ determines by gender. http://www.hopkinsmedicine.org/Press_releases/2006/04_10_06.html accessed 15/04/06.