Twenty‐four‐hour subjective and pharmacological effects of ad‐libitum electronic and combustible cigarette use among dual users

Background and aimsRelative pharmacological effects of e-cigarettes and cigarettes during 24 hours of ad-libitum use have not been described. In this study, 24-hour blood plasma nicotine concentrations and 48-hour subjective effects with use of cigarettes and e-cigarettes were measured among dual users.DesignTwo-arm within-subject cross-over design with preferred e-cigarette or cigarette ad-libitum use over 48 hours.SettingHospital research ward in San Francisco, California, USA.ParticipantsThirty-six healthy dual users of e-cigarettes and cigarettes (n = 8, 25% females).MeasurementsTwenty-four-hour blood plasma nicotine and cotinine concentrations and 48-hour self-reported nicotine withdrawal symptoms and rewarding effects.FindingsAnalyses used analysis of variance (ANOVA)-based mixed models with order of product (e-cigarette or cigarette) and product type (combustible cigarette or type of e-cigarette) as fixed effects, and subject as a repeated effect. During a 24-hour period, e-cigarettes produced lower nicotine exposure than cigarettes for the majority of users, although 25% received more nicotine from e-cigarettes, which was predicted by more frequent e-cigarette use or greater dependence. Compared to cigarette smoking, nicotine exposure for variable-power tank users was similar, while cig-a-like (t(30)  = 2.71, P = 0.011, d = 0.745) and fixed-power tank users (t(30)  = 3.37, P = 0.002, d = 0.993) were exposed to less nicotine. Cigarettes were rated higher than e-cigarettes on some desirable subjective effects (e.g. psychological reward, t(322)  = 7.24 P