Medically assisted rehabilitation (MAR) was established as a treatment modality in Norway in 1998. Today, the program is nationwide, and a recent evaluation showed large regional differences in practice. The Directorate for Health and Social Affairs is in the process of developing a national guideline for MAR, and commissioned the Norwegian Knowledge Centre for the Health Services to retrieve research based evidence for pharmacological treatment.

The main clinical question for this systematic review was to evaluate effects of methadone, buprenorphine and naltrexone, respectively. We selected studies from two recent reports from National Institute for Health and Clinical Excellence (NICE), and relied on the study quality assessments that had already been carried out. In addition, we evaluated the reliability of the pooled effect estimates with the use of the tool GRADE.

We included five systematic reviews and 17 recent single studies from the NICE report on methadone and buprenorphine therapy, and the entire report on naltrexone treatment (one systematic review and 25 single studies). Fewer persons treated with methadone, buprenorphine or naltrexone used illicit opiates than in the control groups. These effects were assessed to be reliable. Further, there were methodological reasons to trust that methadone therapy increases retention rates compared with no pharmacotherapy or with buprenorphine. For naltrexone, there was no difference in retention between intervention and control groups. The results did not give a sufficiently robust basis to claim that pharmacological therapies reduce mortality, that additional psychosocial interventions or higher methadone doses are effective, or that retention rates are higher in specialist services than in primary care. However, the evidence base for these outcomes were of modest to low quality, and more research is needed to conclude.

Several secondary clinical questions on pharmacotherapies for opiate dependence remained unanswered due to gaps in quality research, but it was clear that all three agents were effective in reducing illicit opiate use.