Aims Opioid substitution treatment has been studied extensively in industrialized countries, but there are relatively few studies in developing/transitional countries. The aim of this study was to examine the effectiveness of opioid substitution treatment (OST) in less resourced countries. Design Longitudinal cohort study. Setting Purposively selected OST sites in Asia (China, Indonesia, Thailand), Eastern Europe (Lithuania, Poland, Ukraine), the Middle East (Iran) and Australia. Participants Seven hundred and twenty-six OST entrants. Measurements Participants were interviewed at treatment entry, 3 and 6 months. Standardized instruments assessed drug use, treatment history, physical and psychological health, quality of life, criminal involvement, blood-borne virus (BBV) risk behaviours and prevalence of human immunodeficiency virus (HIV) and hepatitis C. Findings Participants were predominantly male, aged in their early 30s and had attained similar levels of education. Seroprevalence rates for HIV were highest in Thailand (52%), followed by Indonesia (28%) and Iran (26%), and lowest in Australia (2.6%). Treatment retention at 6 months was uniformly high, averaging approximately 70%. All countries demonstrated significant and marked reductions in reported heroin and other illicit opioid use; HIV (and other BBV) exposure risk behaviours associated with injection drug users (IDU) and criminal activity, and demonstrated substantial improvement in their physical and mental health and general wellbeing over the course of the study. Conclusions OST can achieve similar outcomes consistently in a culturally diverse range of settings in low- and middle-income countries to those reported widely in high-income countries. It is associated with a substantial reduction in HIV exposure risk associated with IDU across nearly all the countries. Results support the expansion of opioid substitution treatment.
