Young people who inject drugs (PWID) who undergo opioid
agonist maintenance therapy with methadone or buprenorphine have more than a
60% reduced risk of acquiring hepatitis C virus (HCV) over time
compared to those with no substance use treatment, according to a study presented on Monday at the American Association for the Study
of Liver Diseases (AASLD) Liver Meeting in Boston. Findings were also published in the October
27 edition of JAMA Internal Medicine.
HCV is
readily transmitted through contact with blood, which can occur when people
share syringes and other equipment for injecting drugs. In most developed
countries, shared injection equipment is the major route of HCV transmission.
Maintenance
or substitution therapy using opioid agonists like methadone or
buprenorphine has been shown to be effective in treating addiction to opiates
such as heroin. Opioid agonists, which use the same
brain receptors as opiates, can prevent withdrawal symptoms but typically do
not produce a 'high' at the doses used for maintenance therapy. By
enabling people to inject drugs less often or not at all, maintenance
therapy may help reduce exposure to HCV.
Kimberly
Page from the University of New Mexico Health Sciences Center, Judith Tsui from
Boston University School of Medicine and colleagues evaluated whether opioid
agonist therapy was associated with a lower incidence of HCV infection among
young adult drug injectors, who are vulnerable to infection soon after they start
injecting.
The UFO Study is a prospective,
observational cohort study of young (under age 30) active injection drug users in
San Francisco. Participants were enrolled in three waves (January 2000,
February 2003 and May 2010) and followed through August 2013.
Follow-up interviews and blood testing for HCV were performed quarterly.
Incident (new) HCV infection was defined as a new positive HCV antibody or HCV
RNA test result following a previous documented negative test, or a positive
HCV RNA test coinciding with a negative antibody test, which indicates acute or
recent infection.
The study compared people who underwent various types
of substance use treatment within the past three months: opioid agonist
maintenance therapy, detoxification using an opioid agonist (without ongoing maintenance therapy),
non-opioid agonist forms of treatment (such as 12-step programmes or counselling)
or no treatment.
This
analysis included 552 young people (out of 1548 initially screened) who had injected drugs within the past 30 days and
who tested negative for HCV at study entry. A majority were men and 73% were
white. The median age was 23 years and they had been injecting for a median of
3.6 years. More than two-thirds had been homeless in the past three months and about
one-quarter were recently incarcerated. The most commonly used drug was heroin,
reported by 60%, and one-third said they injected daily. Most participants
(82%) reported no substance use treatment during the prior year.
A total of 171 new HCV infections occurred during an
observation period of 680 person-years, resulting in an overall incidence rate of 25.1
per 100 person-years.
The HCV infection rate was lowest among participants
on opioid agonist maintenance therapy, at 8.6 per 100 person-years. The
infection rate was moderate for people using non-opioid agonist treatment
methods (such as 12-step programmes), 17.9 per 100 person-years. Participants using no substance use
treatment had an incidence rate of 28.2 per 100 person-years, and the highest
rate was seen among people who used opioid agonist detoxification, at 41.1 per
100 person-years.
Compared to people with no substance use treatment,
participants who used opioid maintenance therapy had a statistically
significant 69% lower risk of infection. In an adjusted analysis taking into
account other factors such as demographics, duration of injection and
incarceration, the risk reduction was 61%, and still significant.
Participants using non-opioid methods had a 29% lower
risk of acquiring HCV, while those who used opioid agonist detox had a 39%
higher risk in the adjusted analysis, neither of which were statistically
significant.
In terms of limitations, the researchers noted that since the
majority of study participants were not using substance use treatment, the
comparisons across treatment types involved small numbers. There were not
enough people to compare methadone versus buprenorphine.
Nevertheless, the 61% risk reduction seen in this
study falls within the range seen in other studies of opioid agonist therapy,
such as a 53%
reduction in Vancouver, Canada and an 82%
reduction in Sydney, Australia.
"In this study of young adult injectors, we found that
maintenance opioid agonist therapy (methadone or buprenorphine)
for opioid use disorders was associated with more than a 60% reduction in HCV
incidence over time compared to no treatment," the researchers concluded.
"Our results suggest that treatment for opioid use
disorders with maintenance opioid agonist therapy can reduce
acquisition of HCV in young adult injectors, and should be offered as an
important component of comprehensive strategies for primary HCV
prevention," they added.