Study design and participants
expired breath
RECRUITMENT, BLEEDING DISORDERS
This study was designed as a randomized, open-label, crossover trial conducted in a confinement setting to independently assess the abuse liability of three commercially available ENDS products, compared to subjects’ usual brand (UB) combustible cigarettes and nicotine gum (ClinicalTrials.gov identifier: NCT03126357). The results on one of the product, Vuse Solo G2, were published previously along with detailed information on study methods and proceduresPotential participants were recruited via standard advertisements (print media, radio, and television) and through recruitment databases. Eligible participants were men and women aged 21–60 years in generally good health who self-reported smoking at least 10 filtered non-menthol 83–100 mm combustible cigarettes per day for 6 months or longer. The first cigarette of the day had to typically be smoked within 30 min of waking, and participants were not to have used an ENDS in the 30 days prior to screening. Smoking status was confirmed via levels of carbon monoxide in expired breath at screening (≥ 15 ppm). Smokers who expressed an interest in quitting within 30 days of screening, who were pregnant or breastfeeding, or who were using systemic estrogen-containing contraception or hormone-replacement therapies were excluded. Other key exclusion factors were hemoglobin levels lower than 12.5 g/dl (women) or 13.0 g/dl (men), a history of bleeding disorders, and a recent whole blood donation. All subjects underwent an informed consent process prior to any study procedures, and once enrolled, were informed that they could leave the study at any time.