Benzodiazepines are commonly used in combination with opioids, both clinically and non-medically (Jones et al., 2012, Votaw et al., 2019). Increasing concerns around the concurrent use of benzodiazepines and opioids have emerged in the context of the opioid overdose crisis. In response to growing evidence demonstrating risks of overdose and death when combining benzodiazepines with opioids (Dasgupta et al., 2016, Jones and McAninch, 2015, Park et al., 2015), the United States Food and Drug Administration (FDA) released a drug safety communication in 2016 advising clinicians to avoid co-prescribing these medications when possible (FDA, 2016). Methadone and buprenorphine are opioids recommended as first-line medications for opioid use disorder (MOUD). With rapidly increasing overdose deaths involving high potency synthetic opioids, such as fentanyl, the harm caused by untreated opioid use disorder (OUD) likely outweighs the risks of combining these MOUD with benzodiazepines. As such, in 2017, the FDA released an update stating that methadone and buprenorphine should not be withheld from patients taking benzodiazepines (FDA, 2017). Despite this guidance, clinicians continue to face challenges assessing risks of benzodiazepine use among patients with OUD that may influence decisions to initiate, dose reduce, or discontinue MOUD, particularly with the full opioid agonist, methadone.

Current evidence regarding the impact of benzodiazepines on methadone treatment retention is mixed. Retention in methadone treatment represents a particularly important outcome as longer treatment duration is associated with decreased substance use, overdose death, criminal activity, and HIV seroconversion, especially with treatment courses of at least 12 months (Hubbard et al., 2003, Simpson, 1981). While several studies have demonstrated decreased treatment retention among patients with OUD taking benzodiazepines (Franklyn et al., 2017, Peles et al., 2014, Schiff et al., 2007, White et al., 2014), others have found no significant associations (Brands et al., 2008, Kellogg et al., 2006, Krawczyk et al., 2021, Torrens et al., 1996).

Clarifying this discrepancy is vital given the high prevalence of benzodiazepine exposure among patients with OUD. Specifically, among those receiving methadone treatment, 47–93% reported lifetime use of benzodiazepines and 44–70% reported recent or current use (Chen et al., 2011, Gelkopf et al., 1999, Iguchi et al., 1993, Stitzer et al., 1981). More recent evidence attempting to clarify this relationship has focused on prescription status, indicating that patients using non-prescribed benzodiazepines are twice as likely to discontinue methadone treatment compared to those taking prescribed benzodiazepines or none at all (Eibl et al., 2019).

Although studies of methadone retention often frame treatment discontinuation as “patient drop-out,” program factors also contribute to treatment discharge, which may affect retention estimates (Proctor et al., 2019, Reisinger et al., 2009, Villafranca et al., 2006). Innovative treatment models have emerged to identify and remove program factors contributing to methadone discontinuation. Low-threshold programs minimize restrictive policies and promote harm reduction (Kourounis et al., 2016), while open-access models offer walk-in hours to all patients without an appointment allowing for same-day methadone initiation (Madden et al., 2018). Some open-access models have adopted a low-threshold approach to minimize restrictive policies, such as discharging patients for ongoing substance use and inability to pay for services (Madden et al., 2018). During the COVID-19 pandemic, open-access programs were associated with improved timely access to methadone treatment and more common in Canada than in the United States (Joudrey et al., 2021).

The aim of the current study was to determine the impact of baseline benzodiazepine exposure at methadone treatment intake on 12-month retention at an open-access opioid treatment program (OTP). We hypothesized that patients with benzodiazepine exposure at intake would have similar 12-month retention compared to those without benzodiazepine exposure.