Effect of Extending the Duration of Prequit Treatment With Varenicline on Smoking Abstinence: A Randomized Clinical Trial.

Importance: Even with varenicline, the leading monotherapy for tobacco dependence, smoking abstinence rates remain low. Preliminary evidence suggests that extending the duration of varenicline treatment before quitting may increase abstinence. Objective: To test the hypotheses that, compared with standard run-in varenicline treatment (1 week before quitting), extended run-in varenicline treatment (4 weeks before quitting) reduces smoking exposure before the target quit date (TQD) and enhances abstinence, particularly among women. Design, Setting, and Participants: This double-blind, randomized, placebo-controlled clinical trial enrolled participants from October 2, 2017, to December 9, 2020, at a single-site research clinic in Buffalo, New York. Of 1385 people screened, 320 adults reporting smoking 5 or more cigarettes per day (CPD) were randomized and followed up for 28 weeks. Data were analyzed from August 2021 to June 2022. Interventions: In the pre-TQD period (weeks 1-4), the extended run-in group received 4 weeks of varenicline; the standard run-in group received 3 weeks of placebo followed by 1 week of varenicline. Both groups received open-label varenicline during weeks 5 to 15 and brief quit counseling at 6 clinic visits. Main Outcomes and Measures: The primary outcome consisted of cotinine-verified (at end of treatment [EOT]) self-reported continuous abstinence from smoking (in CPD) during the last 4 weeks of treatment. Secondary outcomes included bioverified self-report of continuous abstinence at the 6-month follow-up and percentage of reduction in self-reported smoking rate during the prequit period (week 1 vs week 4). Results: A total of 320 participants were randomized, including 179 women (55.9%) and 141 men (44.1%), with a mean (SD) age of 53.7 (10.1) years. Continuous abstinence during the final 4 weeks of treatment (weeks 12-15; EOT) was not greater in the extended run-in group (64 of 163 [39.3%]) compared with the standard run-in group (57 of 157 [36.3%]; odds ratio [OR], 1.13 [95% CI, 0.72-1.78]), nor was the hypothesized group × sex interaction significant (OR, 0.52 [95% CI, 0.21-1.28]). Similar nonsignificant results were obtained for continuous abstinence at the 6-month follow-up. The mean (SE) decrease in self-reported smoking rate during the prequit period was greater in the extended run-in group (-38.8% [2.8%]) compared with the standard run-in group (-17.5% [2.7%]). Conclusions and Relevance: Among adult daily smokers, extending the duration of prequit varenicline treatment beyond the standard 1-week run-in period reduced prequit smoking exposure but, more importantly, did not significantly improve continuous abstinence rates. Trial Registration: ClinicalTrials.gov Identifier: NCT03262662.