A few key conclusions and discussion points regarding the state and future of HAT can be offered based on the above review of completed or ongoing studies.
First, although the basic goal of the different HAT studies is similar, each of the studies is distinct in key aspects, thus limiting direct comparisons and meta-analyses.40
Although this might be a desirable goal for science, it should be noted that heroin addiction and its consequences occur in distinct real-life environments (including unique cultural and system factors), and interventions need to be devised, measured, and evaluated within these to have authentic relevance for policy and practice.33,41
Second, the discussed studies above have demonstrated in several different contexts that the implementation of HAT is feasible, effective, and safe as a therapeutic intervention.21,24,26,30
This should not be seen as a conclusion that could be taken for granted because many observers expected disastrous consequences from the provision of medical heroin prescription.
Third, even within the contexts of relevant methodological constraints, e.g., the Swiss study relying purely on prospective observational data, and most of the other RCTs comparing HAT outcomes against a control intervention (MMT), which participants have previously either rejected by choice or proven to be ineffective, 32,42
the reviewed HAT studies have demonstrated rather robust and consistently positive therapeutic outcomes on the various indicators chosen for a population of high-risk heroin addicts for whom currently no effective alternative therapies are available. Clearly, this demonstrated effectiveness is at this point limited to short-term outcomes, and long-term examinations ought to follow (albeit Swiss follow-up data present initial positive evidence in this regard).43
It may very well emerge that HAT’s main long-term benefit does not materialize through life-long maintenance, but by stabilizing and readying many of its patients for other simpler therapeutic interventions or even abstinence.
Fourth, also given the current expansion and diversification of alternative oral opioid maintenance therapies (e.g., buprenorphine and morphine) and considering the complex logistics (on both providers and patients’ ends), high costs, and sociopolitical controversy around (especially injection) HAT, the most sensible role of HAT is likely that of an exceptional “last resort” option for heroin addicts who cannot be effectively attracted into or treated in other available therapeutic interventions.44,45
Granted the above, the primary emerging challenge for science—rather than conducting new and more HAT effectiveness studies—is to provide evidence-based guidelines on how to effectively match existing heroin addict profiles and needs with existing treatment options. This challenge has recently been complicated—in at least some jurisdictions—with the increasing diversification of heroin into poly-opioid (e.g., prescription) use profiles.46
Finally, after extensive HAT research efforts over the past decade, the principal onus of action has shifted from the scientific to the political arena in the jurisdictions under study.12,18
Despite the overall positive results of completed HAT trials undoubtedly justifying some role of HAT in the addiction treatment landscape, authorities in only two countries, Switzerland and the Netherlands, have decisively acted on this issue.34
In the other countries where HAT studies have been completed, Germany and Spain, political decision makers have resisted to convert the beneficial evidence into the necessary politico-legal framework for a more regular offering of HAT as part of the treatment system. Similar hesitation must be expected for Canada after the completed NAOMI trial, and it is a historical fact that the Australian government stopped a comprehensively prepared HAT study project for political reasons in the mid-1990’s.47
The pressure was primarily on science to produce the evidence basis on HAT—the pressure is now on politics to use the evidence generated in the interest of reduced harms and costs related to the problem of heroin addiction.