therapy reduces the risk of HIV infection by half for individuals who inject drugs, according to the results of a systematic review and meta-analysis
published in the British Medical Journal.
“There is evidence
from published and unpublished observational studies that opiate substitution
treatment is associated with an average 54% reduction in the risk of new HIV
infections among people who inject drugs,” write the investigators. “To our
knowledge this is the first study that synthesises the available evidence and
generates a quantitative estimate of the impact of opiate substitution
treatment on incidence of HIV.”
Injecting drug users
are among the groups most affected by HIV. Up to 40% of injecting drugs users
in some settings are infected with the virus, and emerging epidemics in parts
of Russia, eastern Europe and Asia are largely driven by injecting drug use.
buprenorphine are prescribed to people who are dependant on opiates, and both
drugs are on the World Health Organization list of essential medicines. In
addition to reducing craving for illicit substances, therapy with these drugs
has been shown to have other benefits. These include reductions in drug-related
mortality, reduced offending and improved adherence to antiretroviral therapy.
There is also some
evidence that injecting drug users who are prescribed opiate substitution
therapy have a reduced risk of infection with HIV.
An international team
of investigators wanted to establish a clearer understanding of the impact of
opiate substitution treatment in relation to HIV incidence among injecting drug
conducted a systematic review and meta-analysis of the results of randomised
studies, prospective cohort studies, or case-control studies that directly
examined the effect of opiate substitution therapy on HIV incidence in
injecting drug users.
Studies published up
to March 2011 were included in the investigators’ analyses.
A total of 15 studies
were identified. All looked at the impact of methadone maintenance therapy. The
size of the studies ranged from 80 to 2546 individuals; the
duration of follow-up was between one and 20 years; and the research was
published between 1992 and 2009.
The authors were able
to pool the results of nine studies to assess the impact of opiate substitution
treatment in relation to HIV transmission. The results of these studies
provided 819 incident HIV infections over 23,607 person-years of follow-up.
substitution treatment reduced the risk of infection with HIV by 54% (RR =
0.46; 95% CI, 0.32-0.67, p < 0.001).
The authors then
restricted their analysis to the six studies that adjusted for confounders. A
total of 450 incident infections were reported in these studies over 10,064
person-years of follow-up. Methadone substitution therapy reduced the risk of
infection with HIV by 40% (RR = 0.60; 95% CI, 0.42-0.85, p = 0.004).
A significant benefit
of opiate substitution therapy on HIV transmission risk continued to be evident
when the authors restricted their analysis to the five studies with the lowest
risk of bias (RR = 0.61; 95% CI, 0.41-0.91, p = 0.016).
There was no evidence
that the benefits of opiate replacement therapy differed by region or were
affected by the provision of incentives to people. However, there was a weak
association between longer duration of substitution therapy and greater benefit
in terms of reduced HIV incidence.
Four studies looked at
the impact of methadone detoxification treatment. There were 687 incident HIV
infections over 20,616 person-years of follow-up in these studies. The pooled
results showed detoxification therapy was associated with an increased risk of
infection with HIV when compared to either no treatment or methadone
replacement therapy (RR = 1.54; 95% CI, 1.05-2.26, p = 0.026).
“Our findings further
support and highlight the importance of opiate substitution treatment in the
prevention of HIV among people who inject [opiate] drugs,” comment the
investigators. “These data further support studies showing a range of benefits
of opiate substitution treatment, and support calls for the global increase of
harm reduction interventions to reduce the transmission of HIV between people
who inject drugs and between people who inject drugs and the wider community.”