There were strong positive associations between MMT discontinuation and frequent injection heroin and prescription opioid use. As this is a cohort study and causality cannot be inferred, it may be that participants use more illicit opioids following MMT discontinuation or that individuals with heavy illicit opioid use have more severe OUD and represent a population who may be less likely to successfully be retained on MMT (Duffy & Mackridge, 2013; Peles, Schreiber, & Adelson, 2010). This study also found negative associations between MMT discontinuation and being on higher doses of methadone (i.e. >60 mg per day) and being on longer duration of MMT consistent with previous research (Nosyk et al., 2009). Despite this knowledge, MMT dosing often remains below recommended therapeutic targets. One US national study found that only 23% of participants received MMT doses above 60 mg per day (D’Aunno, Pollack, Frimpong, & Wuchiett, 2014). Similarly, a study in our setting found that 50% of MMT participants received mean daily doses below 60 mg per day (Nosyk et al., 2009). Furthermore, higher MMT dose has been associated with better
