IMPORTANCE: Approximately 85% of individuals receiving opioid agonist therapy for opioid dependence smoke tobacco. Despite the significant health risks associated with smoking-related diseases, there has been limited evaluation of smoking interventions tailored to this population. OBJECTIVE: To determine the effectiveness of an intervention combining nicotine replacement with brief behavioral support in reducing cigarette use. DESIGN, SETTING, AND PARTICIPANTS: This multicenter randomized clinical trial was conducted from April 2022 to October 2023 in 7 specialized opioid agonist therapy clinics in Bergen and Stavanger, Norway. The analyst was blinded to patient groupings. Assessors (study nurses) were not fully blinded to participant allocation. Individuals diagnosed with opioid dependency receiving opioid agonist therapy at participating clinics and smoking at least 1 cigarette per day were eligible for participation. Data analysis was performed from December 2023 through October 2024. INTERVENTION: In addition to standard opioid agonist therapy, participants in the intervention group received a 16-week integrated treatment combining nicotine replacement with brief behavioral support. Participants in the control group received only standard opioid agonist therapy. MAIN OUTCOMES AND MEASURES: The primary outcome was at least a 50% reduction in the number of cigarettes smoked, self-reported as cigarette use in the past 7 days at week 16. The analysis followed intention-to-treat principles. Cigarette use was self-reported as per the timeline-follow-back method. RESULTS: Among the 259 participants (mean [SD] age, 48.5 [10.4] years
80 [30.9%] female), 135 were allocated to the intervention group and 124 to the control group. The odds ratio of at least halving the number of cigarettes smoked was 2.07 (95% CI, 1.14-3.75) in the intervention group compared with the control group. CONCLUSIONS AND RELEVANCE: Providing integrated nicotine replacement and behavioral support at opioid agonist treatment clinics effectively helped opioid-dependent participants reduce the number of cigarettes smoked. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05290025.