Is substitution treatment effective in preventing HIV in injecting opioid users?

HEN summary of a report of the Cochrane Collaboration.

Copyright Cochrane Library, reproduced with permission.

The issue

Injecting drug users face a high risk of exposure to infection with human immunodeficiency virus (HIV) and other bloodborne viruses because of the shared use of injecting devices and because of risky sexual behaviour. In the year 2000, injecting drug use accounted for 61% of all HIV infections in the Russian Federation, 23% in the average of 10 west European countries, 22% in the United States, and 8% in Australia. The spread of HIV/acquired immunodeficiency syndrome (AIDS) among injecting drug users can foster transmission of the virus to the general population, through sexual contacts with people who are not drug users, and further along the chain to unborn children, through infected mothers. There is a widely held view that providing oral substitution treatment for injecting opioid users is an important part of containing the spread of HIV infections.

This report assesses the effectiveness of oral substitution treatment for opioid-dependent, injecting drug users. Effectiveness is assessed in terms of the rate of HIV infection, and the prevalence and frequency of behaviours associated with a high risk of HIV transmission. Such behaviours include injecting drug use, shared use of injecting devices, unprotected sexual intercourse and multiple sexual partners.


Treating opioid-dependent, injecting drug users orally with opioid agonist substitutes is associated with a statistically significant decrease in the percentage of people studied that reported injecting drug use and in their frequency of injection. It was not possible, however, to determine accurately the extent to which reduced drug injections contribute to the overall reduction in opioid use. The duration of the benefit of oral substitution treatment is unclear and the gain may not be sustained following cessation of treatment with opioid agonists, such as methadone, particularly if cessation of treatment is not voluntary. Also, because the diversity of study designs and diversity of means of assessing and reporting on injecting drug use prevent calculation of an overall quantitative estimate of the extent of the decrease, it was not possible to relate the decrease in injecting use to opioid use.

Substitution treatment is also associated with a significant decrease in sharing injecting devices. Reduced sharing may be due to fewer injections, but it is still unclear from the data available. Moreover, it seems that other types of substitutions can achieve similar reductions in the sharing of injecting devices, and reductions may be sustained even after cessation of substitution treatment.

Also, there is an association between substitution treatment and a lower incidence of multiple sexual partners and of trading sex for drugs or money. The data suggest, however, no change, or only a small one, in condom use and sex-related risk behaviour associated with substitution treatment. Since the data available was insufficient, the authors of this synthesis found it difficult to make definitive conclusions.

All the studies in the review found a significant reduction in the overall risk of acquiring HIV for participants, from baseline to follow-up, after initiating substitution treatment. This reduction was attributable largely to the significant reductions in the risk associated with using drugs.

Policy considerations

These findings add to the stronger evidence of the effectiveness of substitution treatment on drug use by other systematic reviews. However, the available data are limited, and the lack of data from randomized, controlled trials limits the strength of the evidence presented in this review. On this basis, this review indicates a need for:

  • providing support for substitution treatment for opioid dependence in countries with emerging HIV and injecting drug use problems, as well as in countries with established populations of injecting drug users; and
  • providing greater consistency in reporting injecting behaviour by reporting statistical information on the number of individuals sharing injecting devices and the frequency of sharing. (These measures are crucial for further research and development of health promotion in the field. In addition, it is desirable to have information on which drugs are being injected by those who continue to inject drugs, even while receiving substitution treatment.)

Type of evidence

The report is a systematic review of 28 original studies of all types (controlled studies, cohort studies and descriptive studies), involving 7 900 participants. The majority of the studies were not randomized controlled studies, which limits the strength of the evidence.

The views expressed in this summary are based on a publication of the Cochrane Collaboration and do not necessarily represent the decisions or stated policy of WHO/Europe.


This report was prepared by The Cochrane Collaboration.