Methadone treatment and associated health and social outcomes after a national manufacturing closure in Mexico: a longitudinal observational cohort study in Tijuana

We aimed to explore associations between the time periods during and after the closure and prevalence of methadone treatment, drug use, mental health and social harms among methadone treatment patients. Methods: We examined these associations among 200 MOUD clinic patients in Tijuana, using log-binomial regressions via generalized estimating equations (GEE) over three six-month response periods during and post-closure (Period 1, during and post: 07/2023-01/2024, Period 2, post, limited availability: 02/2024-07/2024 and Period 3, post, restored availability but fewer clinics open: 08/2024-12/2024). We ran three sets of GEE models to test for potential mediation effects of methadone treatment on associations between response period and deleterious outcomes. Findings: Time period was associated with methadone treatment (i.e., significant decline from 36% in Period 1-13% and 26% in Periods 2 and 3, respectively), and with drug use (opioids, methamphetamine, benzodiazepines, injection use), and mental health (anxiety symptoms) outcomes. Interpretation: 's closure and drug use/mental health outcomes, which was consistent with a partial mediating role, but formal causal mediation could not be established due to data limitations. Although other unmeasured changes may have occurred during the study period, these findings suggest that the methadone shortage may have contributed to prolonged adverse effects on patients and highlight the need for policies that ensure consistent MOUD provision in Mexico, including the authorization of buprenorphine for the treatment of OUD. Funding: This study was funded by the National Institute on Drug Abuse (R01DA049644, K01DA062723, T32DA023356, R33DA061260) and the San Diego Center for AIDS Research, an NIH supported program (P30 AI036214).