Non-prescribed use of opioid agonist medications and associations with non-fatal overdoses: A repeated cross-sectional study across a decade of reduced monitoring (2025)

Introduction: Non-prescribed use of opioid agonist treatment (OAT) medications is a public health concern. This study analyzes the prevalence of non-prescribed use and non-fatal overdoses in Norway in 2013 and 2023, a period marked by an increasingly flexible OAT regimen, and examines associations between non-prescribed use and non-fatal overdoses.
METHODS: Cross-sectional surveys with two convenience samples (n(1) = 611 in 2013, n(2) = 523 in 2023) of street-recruited individuals, who reported recent use of opioids and/or stimulants but were not currently enrolled in OAT, were employed. The primary outcomes were self-reported non-prescribed use of methadone and buprenorphine and non-fatal overdoses in the past month and past year. Covariates included demographics and substance use characteristics.
RESULTS: Non-prescribed use of OAT medications significantly declined from 39.4% in 2013 to 28.1% in 2023 (p < 0.001), as did frequency of use (p < 0.01). There was no change in non-fatal overdoses in the past month (8.2% in both years), though past-year non-fatal overdoses decreased (23.6% in 2013 vs. 15.9% in 2023, p = 0.001). Multinomial regression analyses showed no significant association between non-prescribed OAT use and increased risk of non-fatal overdoses. Instead, factors such as injecting drug use, frequent heroin use, stimulant use, younger age, and female sex were associated with non-fatal overdose risk.
CONCLUSION: Even with an increasingly flexible OAT regimen, non-prescribed use declined among street-recruited participants, and no corresponding increase in non-fatal overdoses was observed. These findings challenge the assumption that reduced monitoring in OAT is linked with higher rates of non-prescribed use and adverse outcomes, such as non-fatal overdoses, among individuals not in OAT.