Opioid Substitution Therapy: Lowering the Treatment Thresholds

Background: Opioid substitution therapy (OST) has been established as the gold standard in treating opioid use disorders. Nevertheless, there is still a debate regarding the qualitative characteristics that define the optimal OST intervention, namely the treatment threshold. The aim of this review is twofold: first, to provide a summary and definition of "treatment thresholds", and second, to outline these thresholds and describe how they related to low and high threshold treatment characteristics and outcomes.

Method: We searched the main databases of Medline, PubMed, PsycInfo, EMBASE, CINAHL and the Cochrane Library. Original published research papers, reviews, and meta-analyses, containing the eligible keywords: "opioid substitution", "OST", "low threshold", "high threshold" were searched alone and in combination, up to June, 2015.

Results: Treatment thresholds were defined as barriers a patient may face prior to and during treatment. The variables of these barriers were classified into treatment accessibility barriers and treatment design barriers. There are increasing numbers of studies implementing low threshold designs with an increasing body of evidence suggesting better treatment outcomes compared to high threshold designs.

Conclusion: Clinical characteristics of low threshold treatments that were identified to increase the effectiveness of OST intervention include increasing accessibility so as to avoid waiting lists, using personalized treatment options regarding medication choice and dose titration, flexible treatment duration, a treatment design that focuses on maintenance and harm reduction with emphasis on the retention of low adherence patients.