Craving and personal functioning as mediators of extended-release buprenorphine efficacy: A four-way decomposition analysis from a randomised trial.
John Marsden, Mike Kelleher, Fiona Cowden et al.
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In 30 seconds
This pre-registered exploratory causal mediation analysis examined whether reduced craving and improved personal functioning helped explain extended-release buprenorphine’s effect on opioid-free days. It used data from a 24-week, multicentre, open-label randomised trial of 314 adults with moderate-to-severe opioid use disorder, comparing extended-release buprenorphine with methadone or sublingual buprenorphine. During weeks 13–24, adjusted mean opioid-free days were 58.5 with extended-release buprenorphine and 48.9 with the comparator (IRR = 1.20, 95% CI = 1.10-1.30; P-value <0.001). Reduced opioid ‘need’ craving showed evidence of mediation; personal functioning did not clearly mediate benefit.
Key findings
- Adjusted mean opioid-free days during weeks 13–24 were 58.5 with extended-release buprenorphine and 48.9 with methadone or sublingual buprenorphine (IRR = 1.20, 95% CI = 1.10-1.30; P-value <0.001).
- Reduced opioid ‘need’ craving showed evidence of indirect mediation (PIE = 1.05, 95% CI = 1.01-1.10; P-value = 0.015).
- Extended-release buprenorphine improved personal functioning (WSAS mean difference -3.79; P-value = 0.014), but WSAS did not clearly mediate treatment benefit (PIE = 1.05; P-value = 0.085).
- Craving imagery and intrusiveness and opioid ‘want’ craving showed small, non-statistically significant indirect effects.
Why it matters
The analysis suggests that the benefit of extended-release buprenorphine on opioid-free days operated mainly through pathways not captured by the measured mediators, with reduced need-related craving a possible contributor. Distinguishing treatment outcomes from their potential mechanisms can help interpret pharmacotherapy trials and supports further study of need-related craving as a proximal mechanistic endpoint.
What to keep in mind
This was an exploratory secondary mediation analysis of a randomised trial. Craving was reduced to binary summaries of absence at all follow-up assessments versus presence at any assessment, and the findings do not establish mediation as a causal mechanism.