Non-prescribed buprenorphine and reduction in illicit opioids use among individuals with opioid use disorder: a longitudinal study
Background: Non-prescribed buprenorphine (NPB) use has increased in the USA. We aim to characterize the longitudinal relationship between cessation of illicit opioid use (heroin, fentanyl, non-prescribed pharmaceutical opioids) over time and use of NPB, substance use treatment, and other psychosocial characteristics.
Methods: A community-based sample of 357 individuals with opioid use disorder (OUD) was recruited in Ohio, USA for baseline and follow-up assessments (every 6 months for 2 years) of drug use, treatment participation, and other health and psychosocial characteristics. A mixed logistic regression model with random intercept and slope was used to assess the significance of baseline and lagged predictors of cessation of illicit opioid use. The primary predictor, proportion of days of NPB use, was time-varying and included with cross-sectional and longitudinal terms to assess the effect of different levels and trends in use. Multiple imputation was used to handle missing data.
Results: Illicit opioid-free days increased over time from an average of 38% of days in 6-months preceding baseline to 73% of days at 24-months. NPB use on a greater proportion of days was significantly associated with greater proportion of illicit opioid-free days (AOR = 1.06, p<.001), but changes in NPB use over time were not associated with changes in proportion of illicit opioid-free days. Older age (AOR = 1.12, p<.05) and greater proportion of days in treatment with medications for OUD (AOR = 1.03, p<0.01) were associated with greater proportion of illicit opioid-free days. Ethnic minority status, longer time since first illicit opioid use, and being employed were significantly associated with lower proportion of illicit opioid-free days (p < .05).
Conclusions: Our findings indicate the positive impacts of NPB use on reduction in illicit opioid use that are comparable to participation in treatment. New clinical and policy approaches are needed to improve treatment service delivery.