Young drug injectors on opioid maintenance therapy have lower risk of hepatitis C infection

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.