NCT04709471.

Study name	E‐cigarette nicotine study
Methods	Design: RCT. Parallel‐group assignment Setting: USA Start date: 20 January 2021. Estimated completion date: September 2021
Participants	Estimated: 75 Eligibility criteria include at least 21 years old, use e‐cigarettes and tobacco cigarettes regularly, not planning to quit in the near future, and not pregnant, breastfeeding or planning to become pregnant or breastfeed in the next 2 months Additional criteria will be evaluated to assess for eligibility.
Interventions	Experimental: Switch to low nicotine e‐cigarettes: switch to e‐cigarettes containing 60% of baseline e‐cigarette nicotine content. Device: Juul e‐cigarette. Participants will switch to Juul pods containing less nicotine. Experimental: Reduce number of e‐cigarette pods: reduce e‐cigarette use to 60% of baseline number of pods per week Behavioural: Reduction: participants will reduce the number of Juul pods that they use No Intervention: Use e‐cigarettes as usual: continue using nicotine e‐cigarettes as usual
Outcomes	Primary outcome measure: Feasibility; time frame: Baseline and the 4‐week reduction period. The investigators will assess compliance with study e‐cigarettes and compare the percentage of non‐study e‐cigarette use between conditions to determine which behaviour‐changing strategy is more feasible. Combustible cigarette smoking; time frame: Baseline and the 4‐week reduction period. The investigators will compare change in number of cigarettes per day between conditions. Cigarette dependence; time frame: Baseline and the 4‐week reduction period. The investigators will compare change in cigarette dependence between conditions using the PATH dependence measure. E‐cigarette dependence: time frame: Baseline and the 4‐week reduction period. The investigators will compare change in e‐cigarette dependence between conditions using the PATH dependence measure. Secondary outcome measure: Cigarette demand; time frame: Baseline and the 4‐week reduction period. The investigators will compare change in cigarette demand using the Brief Assessment of Cigarette Demand task. E‐cigarette demand; time frame: Baseline and the 4‐week reduction period. The investigators will compare change in e‐cigarette demand using a version of the Brief Assessment of Cigarette Demand task adapted for e‐cigarettes.
Starting date	20 January 2021. Estimated study completion date: September 2021
Contact information	Elias M Klemperer, PhD802‐656‐1641, elias.klemperer@med.uvm.edu
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