less likely among individuals who smoke heroin rather than inject it. Heroin users treated before the spread of HIV were 13 times more likely to die prematurely than their age peers. 7 HIV and AIDS have since been added to the causes of premature death, as will hepatitis C-related liver disease in the future. Detoxification Detoxification is the first step in the treatment of opiate dependence that aims at abstinence. 4 To maintain abstinence is much harder than to complete withdrawal; those who complete withdrawal are very likely to return to heroin use without support to prevent relapse. 4 Relapse prevention may involve attendance at self-help groups, residence in a therapeutic community, or the taking of a maintenance opioid drug that prevents withdrawal symptoms and enables heroin users to rehabilitate themselves. 4 Methadone maintenance treatment (MMT) MMT is the most extensively researched form of maintenance treatment for opioid dependence. 8 MMT involves the substitution of the opioid methadone, a long-acting orally administered drug, for the shorter- acting heroin that is usually injected. 9 Methadone is taken once a day because its long duration eliminates opiate withdrawal symptoms for 24–36 h. Given in high doses, it reduces craving for heroin and blocks the euphoric effects of injected heroin, thereby freeing the patient from the daily cycle of seeking out, buying, and using heroin. The model of MMT originally proposed by Dole and Nyswander (high doses of methadone, long duration of treatment, intensive rehabilitative services) was modified during its popularisation in the 1970s in the USA 4 and Australia. 10 The goal of many programmes moved from maintenance towards abstinence from all opioid drugs, including methadone. 4 Effectiveness of MMT The effectiveness of treatments for opioid dependence would ideally be assessed through randomised controlled trials (RCTs). Only five such trials have ever taken place in the 35 years since MMT was introduced. 11 All five trials involved small numbers of patients who were rarely Nature of heroin dependence Dependent heroin users are those who continue to use heroin in the face of difficulties they know or believe to be caused by its use—such as health, legal, and interpersonal difficulties. They typically use heroin daily, develop tolerance to its effects, and experience withdrawal symptoms on abrupt cessation of use. Of the US adult population, 0·4–0·7% will develop heroin dependence at some time in their lives. 1 About one quarter of people who have ever used heroin develop dependence. 1 Dependent heroin users who seek treatment and come to attention through the legal system may have used heroin for decades. 2,3 Periods of daily heroin use are punctuated by cycles of detoxification drug treatment, and incarceration for drug-related offences. The proportion of people who achieve enduring abstinence from opioid drugs after any treatment is small, though it gradually increases with age. The low rates of abstinence after treatment are not surprising given that most dependent heroin users enter drug treatment under pressure from family and friends, or because they have been charged with a drug or property offence. 4 Over 20 years or more of addiction, the chances of treated dependent heroin users becoming and remaining abstinent are roughly equal to their chances of dying prematurely (about a third in each case). 2,3 The remaining third move through a cycle of imprisonment, drug treatment, and active heroin use into their 40s and 50s. 2,3 These people are daily heroin users for 40–60% of the time that they spend outside prison or treatment. 5,6 Dependent heroin users are at increased risk of premature death from drug overdose, violence, infectious disease spread by sharing contaminated injecting equipment, and alcohol-related causes in the substantial minority with concurrent alcohol problems. 2,3 The risk of premature death from overdose and infectious diseases is Role of maintenance treatment in opioid dependence Jeff Ward, Wayne Hall, Richard P Mattick SEMINAR THE LANCET • Vol 353 • January 16, 1999 221 Lancet 1999; 353: 221–26 Division of Psychology, Australian National University, Canberra (J Ward PhD) and National Drug and Alcohol Research Centre (NDARC), University of New South Wales, Sydney 2052, Australia (Prof W Hall PhD, R P Mattick PhD) Correspondence to: Professor Wayne Hall (e-mail: ndarc1@unsw.edu.au) Seminar Methadone maintenance treatment (MMT) involves the daily administration of the oral opioid agonist methadone as a treatment for opioid dependence—a persistent disorder with a substantial risk of premature death. MMT improves health and reduces illicit heroin use, infectious-disease transmission, and overdose death. However, its effectiveness is compromised if low maintenance doses of methadone (<60 mg) are used and patients are pressured to become prematurely abstinent from methadone. Pregnancy and psychiatric comorbidity are not contraindications for MMT. As an alternative to MMT, other oral opioid agents (eg, naltrexone, buprenorphine) may increase patient choice and avoid some of the more unpleasant aspects of MMT. The public-health challenge for the future is to develop and continue to deliver safe and effective forms of opioid maintenance treatment to as many opioid-dependent individuals as can benefit from them.