Modeling the impact of spatial inequities in access to medications for treatment of opioid use disorder among persons who inject drugs

Background: Access to treatment and medication for opioid use disorder (MOUD), such as methadone, is essential for improving health outcomes by reducing infection and overdose risks associated with injection drug use. MOUD resource distribution, however, is often a complex interplay of social and structural factors that result in nuanced patterns reflecting underlying social and spatial inequities. Persons who inject drugs (PWID) that receive MOUD treatment experience a reduction in the number of daily drug injections and a reduction in the number of syringe sharing episodes with other individuals. We assessed the impact on reduction in syringe sharing behaviors among PWID who are adherent to methadone treatment via simulation studies. Methods: Actual (real-world) and counterfactual scenarios of varying levels of social and spatial inequity to providers of methadone were evaluated using HepCEP, a validated agent-based model of syringe sharing behaviors among people who inject drugs (PWID) in metropolitan Chicago, Illinois, U.S.A. Synthetic spatial distributions reflecting disparate geographic patterns of methadone provider location and population characteristics are evaluated to show how population-level health outcomes vary accordingly. Results: For all methadone access assumptions and provider location distributions, redistributing methadone providers results in some areas with poor access to MOUDs. All scenarios exhibited some areas with poor access, highlighting the scarcity of providers in the region as a major challenge. Need-based distributions are more like the actual provider distribution, indicating that the actual spatial distribution of methadone providers already reflects the local need for MOUD resources. Conclusions: The impact of the spatial distribution of methadone providers on syringe sharing frequency is dependent on access. When there are significant structural barriers to accessing methadone providers, distributing providers near areas that have the greatest need (as defined by density of PWID) is optimal. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work is supported by the National Institute on Drug Abuse grant U2CDA050098 (The Methodology and Advanced Analytics Resource Center), the National Institute of General Medical Sciences grant R01GM121600, by the U.S. Department of Energy under contract number DE-AC02-06CH11357, and was completed with resources provided by the Laboratory Computing Resource Center at Argonne National Laboratory (Bebop cluster). The research presented in this paper is that of the authors and does not necessarily reflect the position or policy of the National Institute on Drug Abuse or any other organization. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors