Individuals with opioid use disorder may face a number of barriers to initiation of, and retention in, oral OAT, including inadequate management of opioid cravings and withdrawal symptoms despite appropriate OAT dose adjustments; adverse events associated with oral OAT; contraindications to one or more oral OAT medications; insufficient improvements in health, social function, or quality of life; or patient preference to not initiate oral OAT. Injectable opioid agonist treatment (with injectable diacetylmorphine or injectable hydromorphone) is a component of the continuum of OUD treatment that is generally considered for individuals with severe OUD who inject opioids and have not adequately benefitted, or are not expected to benefit, from oral OAT options for the reasons cited above.268,269

Meta-analyses to date have shown that, among individuals who are treatment refractory to methadone, prescription injectable diacetylmorphine—administered under the supervision of trained health professionals in a clinic setting—reduces unregulated opioid use, treatment drop-out, criminal activity, incarceration, and mortality.270-273 A 2011 Cochrane Review that examined eight randomized controlled trials found that the supervised injection of diacetylmorphine, paired with flexible doses of methadone, was superior to oral methadone alone in retaining patients who had not previously benefited from methadone in treatment and reducing the use of unregulated drugs.270 The authors of the Cochrane review concluded that there is value in co-prescribing diacetylmorphine with flexible doses of methadone and that, due to the higher risk of adverse events, treatment with diacetylmorphine should be considered for those who have not benefited from oral opioid agonist treatment.270 In 2015, the lead investigators of iOAT treatment trials conducted a systematic review and meta-analysis on the efficacy of injectable diacetylmorphine, to complement the Cochrane Review.271 Six randomized controlled trials (in Switzerland, the Netherlands, Spain, Germany, Canada, and England) were identified and included in the analysis, which found greater reductions in unregulated heroin use among individuals who received supervised injectable diacetylmorphine compared to those who received oral methadone treatment only.271 Further supporting the use of iOAT for those who have not benefitted from oral OAT, a 2017 evidence review undertaken and released by Public Health Ontario concluded that the available literature on iOAT demonstrates efficacy for iOAT over methadone in terms of treatment retention, reduction in unregulated drug use, and reduction in criminal activities.274

It should be noted that, despite the evidence base supporting the efficacy of iOAT, the resource intensive nature of iOAT programs has limited its accessibility in many jurisdictions across BC.