Methods A structured search strategy encompassing databases including MEDLINE, Embase, CINAHL Plus, PsycINFO and Cochrane Library was implemented from inception to October 2023. Included studies focused on interventions targeting opioid reduction in adults following major surgeries. The risk of bias was evaluated using Cochrane risk-of-bias tool V.2 (RoB 2) and non-randomised studies of interventions (ROBINS-I) tools, and Cohen’s d effect sizes were calculated. BCTs were identified using a validated taxonomy.

Results 22 studies, comprising 7 clinical trials and 15 cohort studies, were included, with varying risks of bias. Educational (n=12), guideline-focused (n=3), multifaceted (n=5) and pharmacist-led (n=2) interventions demonstrated diverse effect sizes (small-medium n=10, large n=12). A total of 23 unique BCTs were identified across studies, occurring 140 times. No significant association was observed between the number of BCTs and effect size, and interventions with large effect sizes predominantly targeted healthcare professionals. Key BCTs in interventions with the largest effect sizes included behaviour instructions, behaviour substitution, goal setting (outcome), social support (practical), social support (unspecified), pharmacological support, prompts/cues, feedback on behaviour, environmental modification, graded tasks, outcome goal review, health consequences information, action planning, social comparison, credible source, outcome feedback and social reward.

Conclusions Understanding the dominant BCTs in highly effective interventions provides valuable insights for future opioid tapering strategy implementations. Further research and validation are necessary to establish associations between BCTs and effectiveness, considering additional influencing factors.

PROSPERO registration number CRD42022290060.