Depot buprenorphine as an opioid agonist therapy in New South Wales correctional centres: a costing model

BACKGROUND: In 2019 daily liquid methadone and sublingual buprenorphine-naloxone were primary opioid agonist treatments for correctional centres in New South Wales, Australia. However, both had significant potential for diversion to other patients, and their daily administration was resource intensive. An alternative treatment in the form of subcutaneous depot buprenorphine became a viable option following a safety trial in 2020 – the UNLOC-T study. Depot preparation demonstrated advantages over current treatments as more difficult to divert and requiring fewer administrations. This paper reports the results of economic modelling of staffing costs in medication administration comparing depot buprenorphine, methadone, and sublingual buprenorphine provision in UNLOC-T trial facilities. METHODS: The costing study adopted a micro-costing approach involving the synthesis of cost data from the UNLOC-T clinical trial as well as data collected from Justice Health and Forensic Mental Health Network records. Labour and materials data were collected during site observations and interviews. Costs were calculated from two payer perspectives: a) the New South Wales (state) government which funds custodial and health services; and b) the Australian Commonwealth government, which pays for medications. The analysis compared the monthly-per-patient cost for each of the three medications in trial-site facilities during July 2019. This was followed by simulation of depot buprenorphine implementation across the study population. Costs associated with medical assessment and reviews were excluded. RESULTS: The monthly-per-patient New South Wales government service costs of depot buprenorphine, methadone and sublingual buprenorphine were: $151, $379 and $1,529 respectively while Commonwealth government medication costs were $434, $80 and $525. The implementation simulation found that service costs of depot buprenorphine declined as patients transitioned from weekly to monthly administration. Costs of treatment using the other medications increased as patient numbers decreased alongside fixed costs. At 12 months, monthly-per-patient service costs for depot buprenorphine, methadone and sublingual buprenorphine—which would be completely phased out by month 13—were $92, $530 and $2,162 respectively. CONCLUSIONS: Depot buprenorphine was consistently the least costly of the treatment options. Future modelling could allow for dynamic patient populations and downstream impacts for participants and the state health system. TRIAL REGISTRATION: ACTRN12618000942257. Registered 4 June 2018. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12913-022-08687-8.