Slow release oral morphine versus methadone for the treatment of opioid use disorder: a systematic review and meta-analysis

Aims: To assess the efficacy of SROM as a treatment for opioid use disorder as measured by treatment retention, opioid use, and craving through a systematic review and meta-analysis of randomized controlled trials.

Methods: We searched three electronic databases for randomized trials published up to May 2018 and reviewed reference lists of published studies. Trials were included if their participants met the diagnostic criteria for opioid use disorder, with a treatment arm involving SROM. Data were pooled using a random-effects meta-analytic model.

Results: Among 1315 studies reviewed, four unique randomized trials met inclusion criteria (n = 461), and compared SROM with methadone. In the meta-analysis, we observed no significant differences between SROM and methadone in improving treatment retention (risk ratio [RR] = 0.98; 95% Confidence Interval [CI]: 0.94 - 1.02, p = 0.34), and heroin use (RR = 0.96; 95% CI: 0.61- 1.52, p = 0.86). Craving data was not amenable to meta-analysis but overall implied that SROM reduces heroin cravings to a greater extent than methadone (P < 0.0001, measured using a visual analogue scale; P = 0.010, measured using the heroin craving questionnaire). As well, results implied no significant differences between SROM and methadone on self-reported use of heroin, cocaine, or benzodiazepines. Available data implied no differences in adverse events.

Conclusions: Meta-analysis of existing randomized trials suggests SROM may be as effective in retaining patients in treatment and reducing heroin use as methadone while potentially resulting in less craving. While methadone is effective for many patients, these findings suggest SROM may provide benefits in addressing some of the limitations of methadone and the need to expand uptake and retention of individuals on opioid use disorder treatments.