Differences in nicotine intake and effects from electronic and combustible cigarettes among dual users.

Aim To describe systemic nicotine exposure and subjective effects of electronic cigarettes (e-cigarettes) in people who use both e-cigarettes and cigarettes (dual users), including within-subject comparisons of e-cigarette and cigarette use. Design Two-arm, counterbalanced cross-over study. Participants used their usual brand of e-cigarette or cigarette during a standardized session in a 2-week study. Setting Hospital research ward, San Francisco, CA, USA. Participants Thirty-six healthy (eight women, 28 men) participants. Measurements Plasma nicotine was analyzed by gas chromatography-tandem mass spectrometry; nicotine withdrawal, urge to smoke and vape, affective states, craving, satisfaction and psychological reward were measured by standardized questionnaires. Findings Compared with cigarettes, average maximum plasma nicotine concentration (C-max) was lower with e-cigarettes [6.1 +/- 5.5 ng/ml, mean +/- standard deviation (SD) versus 20.2 +/- 11.1 ng/ml, P < 0.001] and time of maximal concentration (T-max) was longer (6.5 +/- 5.4 versus 2.7 +/- 2.4 minutes, P < 0.001). Use of both products resulted in a reduction in the severity of withdrawal symptoms, negative affect and urge to use either product. E-cigarettes were less rewarding and satisfying and reduced craving to a lesser degree than cigarettes. We were not able to detect any differences in withdrawal symptoms, affective states and urge to smoke cigarettes between e-cigarette and cigarette use. Conclusion Systemic nicotine exposure was, on average, lower with single use of e-cigarettes compared with cigarettes, and e-cigarettes were judged to be less satisfying and rewarding and reduced craving less than cigarettes.