Opioid use disorder (OUD) is a public health concern worldwide (Degenhardt et al., 2014, Degenhardt et al., 2019, UNODC, 2022) and is defined as a complex and multidimensional phenomenon in terms of etiology, physical and psychiatric comorbidities, and socio-structural factors (Dydyk et al., 2022, Hser et al., 2017, Jones and McCance-Katz, 2019, Polenick et al., 2019, Rosen et al., 2011, Winkelman et al., 2018). Providing a wide range of effective treatment options is essential to address the multiple harms experienced by people with OUD, which often require long-term treatment (McLellan et al., 2005). The use of medications for OUD is a well-established treatment, with methadone and buprenorphine traditionally offered as first-line therapies (Bell and Strang, 2020, Srivastava et al., 2017, Strang et al., 2020).

Due to personal, treatment, and non-treatment-related factors, not all patients are retained in or benefit from traditional opioid maintenance treatment (OMT) (Nordt et al., 2019, O'Connor et al., 2020). In some countries, an additional treatment option includes heroin-assisted treatment (HAT), where diacetylmorphine (pharmaceutical heroin) is used as the main pharmaco-therapeutic agent. HAT is a highly structured and regulated treatment and entails supervised heroin intake twice daily (Farrell & Hall, 2015). Clinical trials have indicated that compared to oral methadone alone, HAT is cost-effective, reduces crime and drug use, and is superior to regular types of treatment in retaining patients whose needs were not met by traditional OMT (Smart and Reuter, 2022, Strang et al., 2015, Timko et al., 2016).

Supervised HAT was first tested in Switzerland in 1994 as part of a cohort study, and since then, the availability and discourse on HAT have evolved (Boyd and Norton, 2019, Kilmer et al., 2018, Meyer et al., 2022). HAT is currently integrated into the standard treatment systems in Switzerland (Federal Office of Public Health, 2022), the Netherlands (van der Gouwe et al., 2022), Germany (Federal Ministry of Health, 2012), Denmark (Danish Health Authority, 2022) and Canada (Tran & MacDougall, 2022). Pilot HAT projects are ongoing in Luxembourg (Youth and Drug Assistance Foundation, 2022), Norway (University of Oslo, 2021), and Scotland (Glasgow City Council, 2019). Further, HAT trials have been conducted in Canada (Oviedo-Joekes et al., 2008, SALOME, 2016), Spain (March et al., 2006), Belgium (Demaret et al., 2013), and England (Poulter et al., 2022, Strang et al., 2010).

A low demand for HAT has been reported in some settings, likely due to its intensive and restrictive protocol (Bell et al., 2018, Demaret et al., 2014, Strang et al., 2015). A recent study from Switzerland found an initial high demand for HAT after its introduction; however, over time, the proportion of HAT patients (compared to other OMT patients) remained stable (Nordt et al., 2019). This might suggest that this type of treatment addresses the needs of a specific subgroup within the OUD population and does not experience an excessive demand driven by an interest in “free heroin”.

In the context where multiple OUD treatment options are increasingly available, and where treatment and medication type could influence retention and recovery (O'Connor et al., 2020), it becomes relevant to explore the characteristics of patients that start HAT. Having a better understanding of HAT patient characteristics and previous treatment experiences is important for planning and tailoring correct treatment and care. In particular, delineating the profile of individuals initiating HAT and comparing it to other OMT groups could clarify if the target population (often defined as “hard to treat” or refractory to treatment) is successfully reached.

The present study aimed to:

a) describe the characteristics of individuals initiating OUD treatment (with heroin, methadone, or buprenorphine) in Denmark between 2010 and 2018.

b) compare the characteristics and enrollment trends of individuals initiating HAT to the other OMT patient groups in Denmark during the same period.