Substitution treatment of injecting opioid users for prevention of HIV infection.

Substitution treatment of injecting opioid users for
prevention of HIV infection.
Gowing L., Farrell M., Bornemann R. et al.
Cochrane Database of Systematic Reviews: 2011, Issue 8, Art.
No.: CD004145.
Updated review conducted for the respected Cochrane collaboration finds that methadone
maintenance and allied treatments for opioid dependence consistently and significantly
reduce the risk of transmission of blood-borne viruses and curb the spread of HIV.
Summary Drug injectors are vulnerable to infection with HIV and other blood borne
viruses due to the collective use of injecting equipment as well as sexual behaviour. This
review aimed to assess the degree to which this risk is affected by the prescription of
drugs such as methadone to be taken by mouth which substitute for the opiate-type
drugs the patient is dependent. It assessed impacts on behaviours which place people at
high risk of viral transmission and on actual rates of HIV infection. With one exception, it
considered all sorts of studies, not just randomised trials, as long as the treatment and
outcomes were relevant and participants were opioid dependent drug users, most of
whom were currently or recently injecting. The exception was studies which required
patients in treatment to at the same time recall their past risk behaviour before and after
starting treatment. Non-English language studies were included. The studies were
expected largely to relate to methadone, but evidence relating to other oral preparations
(buprenorphine, LAAM, codeine and slow release morphine) was also considered.
A search discovered 38 studies involving about 12,400 participants. Just two randomly
allocated patients to substitute prescribing versus other treatments. In the remaining
studies, findings would have been complicated by influences other than substitution
treatment resulting in potential bias. All but six were solely concerned with methadone
treatment, 32 with treatment in a service specialising in addiction treatment, and 26
were set in the USA. Due to differences between the studies, no attempt was made to
combine their findings in to an overall quantitative assessment of the impacts of the
treatments. Instead the reviewers assessed whether effects were consistent across the
studies and across different types of studies.
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 Overall studies consistently find that after entering oral substitute prescribing treatment
(generally involving methadone), patients move to being at substantially lower risk of
HIV infection due to behaviours linked to their drug use, but less consistently in respect
of their sexual behaviour.
Across 17 studies it was consistently found that starting oral substitution treatment was
associated with significant falls in the proportion of patients who continued to inject and
in the frequency of injecting. These reductions typically occurred in the first one to three
months of treatment and were sustained for at least the first year. However, reductions
were not necessarily sustained after treatment ended, particularly if termination had
been involuntary.
Treatment was also consistently associated with a significant decrease in the sharing of
injecting equipment, possibly due to reduced injecting. These benefits were sometimes
sustained after treatment ended, though not in a study in which patients were forced to
leave due to subsidised treatment no longer being available. In some studies similar
reductions in sharing were achieved by other treatment modalities.
Like another Cochrane review, the featured review also found that illicit opioid use
(injected or not) significantly decreased after entering treatment and did so consistently
across all relevant studies.
Since there were few studies, it was difficult to be conclusive, but the data also
suggested that sex-related risks of viral transmission were also reduced due to fewer
people having multiple partners or exchanging sex for drugs or money, though condom
use was affected little if at all. In six of the seven studies to assess this, the overall drugrelated
risk of HIV infection assessed by composite scales was significantly reduced. The
same was true of the seven studies which assessed risk due to drug use or sexual
behaviour.
Four studies assessed relationships between the proportions of people who became HIV
positive (seroconversion) and their participation in methadone treatment. All found that
participation as such, or more extended or continuous participation, was associated with
a lower rate of seroconversion. This suggests that reductions in risk behaviour do
translate in to actual reductions in cases of HIV infection. Substitution treatment may
also protect individuals already infected with HIV against further infection with other
strains of HIV, or other blood-borne viruses.
The authors' conclusions
The reviewers concluded that oral substitution treatment for injecting opioid users
reduces drug-related behaviours with a high risk of HIV transmission, but has less effect
on sex-related risk behaviours. On this basis, provision of this treatment should be
supported in countries with emerging HIV and injecting opioid use problems as well as
those with established populations of injecting opioid users.