Perspectives on drugs: hepatitis C treatment for injecting drug users

A hidden epidemic of hepatitis C

Hepatitis C is the most common infectious disease in injecting drug users, among whom it is usually transmitted through the sharing of injecting equipment such as needles and syringes. Most of those who become infected go on to develop chronic HCV infection, which can lead to severe health problems in individuals and place a major burden on health care systems. Yet hepatitis C is both preventable and curable, and interventions in this field, particularly the development of new medicines to treat hepatitis C, are making rapid progress.

Hepatitis C virus (HCV) infection is highly prevalent in injecting drug users across Europe, with national infection rates for this group ranging from 18% to 80%. However, infected individuals often show no noticeable symptoms, and many are unaware that they are carrying the virus, leading to it being referred to as a ‘hidden’ epidemic. Injecting opioid users in Europe constitute an ageing population, which includes many who have been living with hepatitis C for 15 to 25 years. The natural history of chronic hepatitis C virus infection (cirrhosis risk escalates after 15 to 20 years) and the ageing cohort effect in this population mean that a large burden of advanced liver disease can be expected over the next decade.

Reducing infections among injecting drug users

Among injecting drug users, the sharing of needles and syringes is the key risk factor for acquiring HCV infection, although there is considerable evidence of a potentially high risk of infection associated with sharing drug-preparation equipment such as cookers, filters, swabs and water (Pouget et al., 2012). However, there is good evidence to show that retention in opioid substitution treatment reduces injection frequency (Gowing et al., 2008), and that it is most effective in reducing HCV transmission when used alongside interventions that support safer injection practices (Hagan et al., 2011). Two studies that examined the independent and combined effects of needle and syringe programmes and opioid substitution treatment on HCV incidence concluded that the combined effect of these two interventions resulted in the greatest reductions in HCV transmission (Turner et al., 2011; Van Den Berg et al., 2007).

Modelling studies have been used to explore the potential effectiveness of different hepatitis C interventions, and these indicate that it may be difficult for opioid substitution treatment and high-coverage (1) needle and syringe programmes to greatly impact on hepatitis C prevalence. Modelling the scale-up of both interventions for the United Kingdom (with 40% baseline chronic hepatitis C prevalence among the target population) shows that they are unlikely to lead to substantial reductions in the prevalence of chronic hepatitis C after 10 years, unless both interventions cover 80% or more of the injecting population (Vickerman et al., 2012).

Hepatitis C treatment as prevention

Recent advances in hepatitis C treatment approaches, including the use of direct-acting antiviral agents and interferon-free treatment regimes show much promise (see panel 4), including the potential for treating hepatitis C among injecting drug users. In this area, modelling studies suggest that hepatitis C treatment could play an important role in preventing spread of the virus. A study by Martin et al. (2011) indicated that a 13% reduction in hepatitis C prevalence might be achieved over 10 years as a result of treating 10 infections per year per 1 000 injecting drug users in injecting drug use populations with 40% prevalence.

Barriers to accessing hepatitis C treatment

In spite of recent improved treatment outcomes for hepatitis C patients, available data show treatment uptake continues to be very low among injecting drug users. The literature highlights a number of possible reasons for this. Service providers cite concerns around adherence, risk of exacerbation of psychiatric disorders and the potential for reinfection after treatment as reasons for not assessing or treating hepatitis C in injecting drug users (Edlin et al., 2001; Soriano et al., 2002). On the part of patients, the lack of access of people who inject drugs to testing still constitutes a key-barrier to entering a care pathway. In addition, poor knowledge about hepatitis C and treatment availability, the absence of noticeable symptoms (Grebely et al., 2011) and the perceived side-effects of treatment (Swan et al., 2010) are named as barriers for accessing hepatitis C care. Finally, until recently, current drug injecting was an exclusion criterion for receiving government-funded hepatitis C antiviral treatment in a number of European countries. This obstacle, however, is now being removed, with most clinical guidelines revised to allow for the treatment of hepatitis C in injecting drug users.

Strategies to improve treatment and care

A number of the lessons learned in responding to the HIV epidemic can be transferred to managing the spread of hepatitis C among injecting drug users, including recognition of the importance of putting in place a set of comprehensive, coordinated and multidisciplinary responses. These need to include the provision of HCV testing, assessment, patient education on the long-term consequences of HCV-related liver disease. The enhancement of treatment uptake is important for injectors and effective treatment options need to be available and easily accessible for this population group. The co-location of hepatitis C treatment and opioid substitution treatment is likely to facilitate user access, and might also be linked with mental health care. Improving treatment adherence among injecting drug users is another area where improvements can be made and the use of case management, support services and provider education and training is likely to enhance care.

Conclusion

This analysis draws attention to the high levels of HCV infection among injecting drug users, both as an urgent public health priority, and as a field that has recently seen major advances in medical interventions. If hepatitis C treatments for injecting drug users are to be effective, they will need to be embedded in and delivered as part of a comprehensive package of interventions. An important area for future investigation will be to review the uptake of hepatitis C treatment among drug injectors, and identify and challenge any barriers that prevent them from receiving an adequate and equitable service.