A systematic review of sex differences in treatment outcomes among people with opioid use disorder receiving buprenorphine maintenance versus other treatment conditions

•Few randomized controlled trials comparing buprenorphine with other medication-assisted treatment, withdrawal management or placebo have conducted sex-specific analyses.•Sex differences in treatment retention, opioid use, other substance use and sexual risk behaviours have been identified, but conclusive statements cannot be made•Further research on sex differences in treatment outcomes among people receiving buprenorphine is needed Opioid use disorder is a major health concern in North America. Currently, buprenorphine is one of the most common pharmacological interventions used to treat opioid use disorder. Despite increasing prevalence of opioid use disorder among females, little is known about sex considerations in relation to treatment with buprenorphine. CINAHL, PsycINFO, EMBASE, PubMed/MEDLINE and Cochrane Central were searched for randomized controlled trials examining buprenorphine maintenance versus other medication-assisted treatment, placebo, or withdrawal management to determine if there were any sex differences in treatment outcomes reported. This review included 25 studies and found that only 52% included information related to sex differences in treatment outcomes or discussed any sex considerations in their studies. Of the 6,466 patients represented by these studies, only 26% were female. Of the studies conducting sex-specific analyses, seven studies examined treatment retention, five examined opioid use, two examined other substance use and one examined sexual risk behaviours. However, due to mixed findings, small sample sizes, and inability to conduct meta-analyses, no conclusive statements can be made about sex differences in these outcomes. None of the studies described sex differences in quality of life, legal involvement or mental and physical health. Low numbers of females have been included in randomized controlled trials examining buprenorphine compared to males. While sex differences in treatment outcomes were identified in this review, further research is needed in order to add to these findings. Future studies should include greater numbers of female participants and conduct sex-specific analyses.