The Pharmaceutical Journal Vol 267 No 7174 p724-725
17 November 2001

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Royal Society of Medicine / Royal College of Psychiatrists summary

Treating addiction: advances and trends

An expected increasing prevalence of drug misuse has implications on targets set by the Government for treatment services, according to TIMOTHY MILLAR, research fellow, Drug Misuse Research Unit, University of Manchester.

One of the Government's key targets set out in its 1998 10-year drug strategy is to increase the participation of drug misusers in treatment programmes by 100 per cent by 2008. However, there is an ambiguity: does this mean increase the proportion by 100 per cent or the actual number, Mr Millar asked. "If it means the number then doubling it could be no good: the actual proportion of drug misusers in treatment might decline if there is an increase in prevalence of drug misuse." He illustrated this using population data for Bolton and Manchester. The number of drug misusers in Manchester is currently much larger than in Bolton but it is stable. In Bolton, there has been a recent sharp increase in the number of young people accessing drug misuse services. Doubling the number of drug misusers in treatment in Bolton by 2008 could result in a smaller proportion of the total drug misusing population in treatment. "We need to consider these probabilities or we will miss the opportunity to tackle the drug misuse problem," he concluded.

JON BASHFORD, project manager, Ethnicity and Health Unit, University of Central Lancashire, said: "There is a changing picture of drug use in black and minority ethnic groups." However, services had not taken these changes into account and they need to be recognised for development of services in the future.

The ethnic minority population is a young and growing one, which is more likely to be poor with high rates of unemployment and proportionally more people in the criminal justice system compared with white populations.

The 1980s heroin "epidemic" occurred in areas with these difficulties: drug use is linked to deprivation and crime, said Mr Bashford. In the 1980s, drug misuse tended to involve white populations and any drug misuse in the black and ethnic minority populations was largely hidden.

However, evidence suggests there is now an increase in use of heroin among Pakistani and Bangladeshi males, an increase in use of cocaine and crack in all black groups, an increase in alcohol abuse among the Sikh population and a general increase in injecting drug use. Access to drug misuse services by ethnic minority populations is poor: people are unaware of the services and believe they do not meet their needs. There is also a lack of knowledge about drugs among parents of drug users leading to fear so that the drug user does not get adequate support.

Neurobiology of addiction

Increasing levels of dopamine in the brain is essential to the addictive potential of any drug, said Dr ANNE LINGFORD HUGHES, senior lecturer in biological psychiatry and addiction, Bristol University.

People do not use a drug again unless it gives pleasure. The key action that all drugs of misuse share is their ability to increase dopamine in the brain: without this increase, drugs would not give pleasure, she explained. Although different drugs work by different chemical mechanisms, their effect on dopamine is the same. Normally, a burst of dopamine is released as a result of a stimuli, such as food, resulting in pleasure followed by a reuptake mechanism which ends the pleasure. Cocaine, for example, blocks the reuptake of dopamine.

A decrease in dopamine response also contributes to the symptoms of withdrawal, such as dysphoria and irritability. Changes in the brain as a result of taking drugs are dramatic and long-lasting.

"As long as four months after cocaine was last used, the normal dopamine system is not functioning normally and this drives further use," Dr Lingford Hughes said. A key indicator of vulnerability to addiction is an under-functioning dopamine system, she added.

The dopaminergic system is modulated by other neurotransmitters, such as opiates and glutamine, and these provide targets for both other drugs of misuse and also pharmacotherapy aimed at reducing misuse. Alcohol stimulates the inhibitory GABA-benzodiazepine system and chronic changes at this receptor mediate tolerance. Alcohol also inhibits the excitatory glutamate system. Chronic alcohol use can lead to over-stimulation of this system and if drinking is stopped, a calcium influx occurs in cells resulting in hyperexcitability, seizures and cell death. Acamprosate blocks this so less cell death occurs. Animal models show that if it is given before alcohol is withdrawn (ie, as part of a detoxification regimen), then cell death can be prevented, she added.

Dr Lingford Hughes commented on the importance of environment in drug misuse: when addicts are given heroin or saline in a laboratory environment, they cannot tell the difference between the two, she said.

Infections

Hepatitis C is the most important cause of liver disease in intravenous drug users, said Dr RICHARD GILSON, senior lecturer in genitourinary medicine, Royal Free Hospital and University College Hospital Medical School, London.

Of people infected with hepatitis C, between 10 and 20 per cent are able to clear the infection but the large majority become chronically infected. However, it is now thought that hepatitis C does not progress as rapidly to liver disease than early studies had suggested, he said.

The rationale of treatment is to prevent eventual progression to liver disease, to improve symptoms (which are often non-specific, eg, fatigue) and to reduce infectivity. Interferon had been the mainstay of treatment until recently but its response rate had been poor. Newer treatments include interferon plus ribavirin, pegylated interferon, and pegylated interferon plus ribavirin. Another combination, interferon plus amantadine, is in clinical trials although early results do not look hopeful, Dr Gilson said.

In terms of treating acute hepatitis C infection, Dr Gilson said that there is some suggestion that if the infection is treated in early stages, it could prevent the patient from becoming a chronic carrier. A trial to be published in The New England Journal of Medicine imminently, demonstrates that giving interferon in the initial stages of infection results in the vast majority of patients (43 out of 44) becoming RNA-negative for hepatitis C infection and remaining so for six months after treatment is stopped, he added.

Dr SIMON EDWARDS, consultant in genitourinary medicine and HIV, University College Hospital London, said that although the number of cases of HIV infection among intravenous drug users has fallen over the past 15 years, there is worrying evidence that people are now sharing needles. A recent anonymous survey has revealed that one in three drug users had shared needles in the past four weeks. Another concern about needle sharing is the absence of needle exchange programmes in prisons.

Progression of HIV to AIDS is no different in intravenous drug users than in other populations. However, drug users are less likely to start treatment than other groups. Those drug users that do comply with treatment have a similar response to non-users.

In terms of which treatment should be used, Dr Edwards said that as long as people take three drugs, which three did not matter. "The most important thing is that people take and adhere to a three-drug regimen." Therefore, the choice is based on factors such as lifestyle, frequency of dosing, drug interactions, and any factors that would stop a patient taking a drug. For drug users, interactions between antiretroviral therapy and methadone have to be considered. Efavirenz and nevirapine both reduce levels of methadone. Some, but not all, patients consequently need an increase in methadone dose. Protease inhibitors could also lower methadone levels.

A useful website giving details of drug interactions with antiretrovirals is www.hiv-druginteractions.org.

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