Effect of e-cigarette flavors on nicotine delivery and puffing topography: results from a randomized clinical trial of daily smokers

Rationale: There is limited understanding regarding how various e-cigarette flavorings may influence the behavior of non-regular e-cigarette users who are regular cigarette smokers. Objectives: To assess differences in nicotine delivery, puffing topography, subjective effects, and user satisfaction from different flavored e-liquids. Methods: Eighteen daily smokers (average age, 44.1 ± 7.0; 9 males; average CPD, 13.0 ± 5.8) smoked their tobacco cigarettes during an initial visit and returned five times to try an e-cigarette (eGo type) refilled with a nicotine solution (24 mg/ml) of five different flavors: cherry, tobacco, espresso, menthol, and vanilla (randomized order). Assessments at each visit included puffing topography, blood samples for nicotine analysis, and subjective reports of nicotine effects and flavor satisfaction. Results: Vaping different flavors resulted in different levels of plasma nicotine. The flavor producing the highest plasma nicotine concentration (C_max) was cherry (median 21.2 ng/ml), which was not significantly different than nicotine delivery from a combustible cigarette (29.2 ng/ml, p >.05). Vanilla e-liquid produced the lowest C_max (9.7 ng/ml), and participants tended to puff less frequently on vanilla compared to tobacco flavor (p =.013). Flavors did not differ significantly in the speed of nicotine delivery (T_max). During controlled use, puff duration for all flavors was significantly longer than a combustible cigarette (p < 0.05). After controlling for nicotine delivery, significant differences in flavor enjoyment were detected. Menthol flavored e-liquid was rated as more enjoyable than vanilla and tobacco flavored e-liquids (p < 0.05). Conclusions: Flavors tested in this study yielded different patterns of nicotine delivery and led to differences in reduction in smoking urges. Trial registration: ClinicalTrials.gov Identifier: #NCT02575885.