Thursday February 11 2010
Drugs such as Valium bind to a particular site in the brain
“Anxiety drugs like Valium are addictive in the same way as heroin,” said the Daily Mail, reporting on research into the actions of the drug.
The researchers say that the family of benzodiazepine drugs such as Valium and Xanax exert their calming effect by binding to a particular site on chemical receptors in the brain. As the drug molecules bind to the chemical receptor, known as a ‘GABA’ subunit, they boost the action of a neurotransmitter, called dopamine. Dopamine affects the part of the brain associated with the sense of reward from some illegal drugs.
The study, conducted in mice, increases our knowledge about the neurological basis for addictive behaviour. However, while dependence is a known side effect of Valium, media comparisons to heroin use seem tenuous. This research was not intended to look at the complex issues involved in substance abuse and addiction. Although the researchers have identified processes common to both addictions, users of Valium should not be concerned by the implications of this study. A GP or pharmacist can offer advice to patients worried about their medication use.
Where did the story come from?
This research was carried out by Dr Kelly Tan and colleagues from the Universities of Geneva and Zurich in Switzerland. The study was supported by grants from the US National Institute on Drug Abuse, the Swiss National Science Foundation, the Swiss Initiative in Systems Biology and the European Commission Coordination Action. The study was published in the peer-reviewed journal Nature.
The Daily Mail and The Daily Telegraph have promoted their stories using photographs depicting heroin use or mental distress. The Daily Mail did not mention that this was an animal study.
What kind of research was this?
In this neuroscience research conducted on mice, the researchers wanted to explore the chemical and biological processes of the nerve cells that result in some people becoming addicted to benzodiazepine (BDZ) medication. They say that benzodiazepine anti-anxiety drugs “are widely used in clinics and for recreational purposes, but will lead to addiction in vulnerable individuals”.
Their mouse study looked at several aspects of how neurotransmitters and receptors within the brain are stimulated by benzodiazepines and how their actions combine to produce their calming effects.
One substance of interest in this research was dopamine, an important chemical neurotransmitter implicated in some other forms of addiction. Dopamine’s normal role is to chemically transmit information between different nerve cells in the brain.
What did the research involve?
The researchers explain that addictive drugs can be classified into three groups according to the cellular mechanism through which they increase dopamine in some parts of the brain. For example, heroin and cannabis act on the receptors attached to special neurons that normally secrete a neurotransmitter called GABA (gamma-aminobutyric acid type A). Other addictive substances work through different pathways.
The pathways for other drugs have been described through previous research, but the authors of this study say the neurological processes behind benzodiazepine drug addiction have not yet been established.
In this research on mice, scientists wanted to test whether BDZ medication worked in a similar way to other addictive substances. To test how the workings of the brain were affected by BDZ the researchers gave mice a single injection of BDZ. They performed several types of analysis on the mice brains, including measuring the ratios of neurotransmitters in the brain, assessing electrical currents and examining the proteins found on the surface of the brain cells.
The researchers analysed their results extensively and have reported these appropriately in the published paper and supplementary tables.
What were the basic results?
The researchers say that benzodiazepines increase firing of dopamine neurons in some parts of the brain. This was due to changes in the GABA receptors found in the spaces between neurons, which, in turn, triggers other dopamine neurons. This process appears to be behind the drug’s addictive potential.
How did the researchers interpret the results?
They say that their work helps “unravel the molecular basis” of the features that benzodiazepines share with addictive drugs. Furthermore, they say they believe their findings “will be key for designing new BDZs with lower addiction liability”.
They hope that the mechanisms uncovered may ultimately explain individual variations in susceptibility to addiction, both for BDZs and for other drugs.
This animal study has been thorough and well conducted. The findings will be of interest to the research community and to those interested in designing drugs that have lower addictive potential. The result of this research may also lead to an improved understanding of the mechanisms behind individuals’ varying susceptibility to addiction, an area that has further research potential.
However, despite the researchers finding that BDZ works using a similar pathway to certain illegal drugs, media comparisons to heroin addiction seems to be quite alarmist. This research has concentrated on identifying neurological processes in mice and not the complex factors involved in substance abuse or drug addiction. Based on this research it seems inappropriate to compare the use of oral diazepam medication to intravenous heroin use, as was depicted by The Daily Telegraph.
Dependence is already a known potential side effect of taking diazepam, which is one of the reasons why guidelines already say that doctors should only prescribe it for short-term use. Anyone concerned with their use of diazepam or valium should consult their pharmacist or GP for further advice.