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Background: More smokers report using e-cigarettes to help them quit than FDA-approved pharmacotherapy., Objective: To assess the association of e-cigarettes with future abstinence from cigarette and tobacco use., Design: Cohort study of US sample, with annual follow-up., Participants: US adult (ages 18+) daily cigarette smokers identified at Wave 1 (W1; 2013-14) of the PATH Study, who reported a quit attempt before W2 and completed W3 (n = 2443)., Exposures: Use of e-cigarettes, pharmacotherapy (including nicotine replacement therapy), or no product for last quit attempt (LQA), and current daily e-cigarette use at W2., Analysis: Propensity score matching (PSM) of groups using different methods to quit., Outcome Measures: 12+ months abstinence at W3 from cigarettes and from all tobacco (including e-cigarettes). 30+ days abstinence at W3 was a secondary outcome., Results: Among daily smokers with an LQA, 23.5% used e-cigarettes, 19.3% used pharmacotherapy only (including NRT) and 57.2% used no product. Cigarette abstinence for 12+ months at W3 was ~10% in each group. Half of the cigarette abstainers in the e-cigarette group were using e-cigarettes at W3. Different methods to help quitting had statistically comparable 12+ month cigarette abstinence at W3 (e-cigarettes vs no product: Risk Difference (RD) = 0.01, 95% CI: -0.04 to 0.06; e-cigarettes vs pharmacotherapy: RD = 0.02, 95% CI:-0.04 to 0.09). Likewise, daily e-cigarette users at W2 did not show a cessation benefit over comparable no-e-cigarette users and this finding was robust to sensitivity analyses. Abstinence for 30+ days at W3 was also similar across products., Limitations: The frequency of e-cigarette use during the LQA was not assessed, nor was it possible to assess continuous abstinence from the LQA., Conclusion: Among US daily smokers who quit cigarettes in 2014-15, use of e-cigarettes in that attempt compared to approved cessation aids or no products showed similar abstinence rates 1-2 years later., Competing Interests: KMC has received payment as a consultant to Pfizer, Inc., for service on an external advisory panel to assess ways to improve smoking cessation delivery in health care settings. KMC also has served as paid expert witness in litigation filed against the tobacco industry. MG receives fees for serving on an advisory board from Johnson & Johnson and grant support from Pfizer. WC reports long-term stock holdings in General Electric Company, 3M Company, and Pfizer Incorporated, unrelated to this manuscript. Westat is a commercial, employee-owned research corporation. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Most electronic cigarettes (e-cigs) aerosolize a nicotine-containing liquid that users inhale. Few experimental studies have examined e-cig abuse liability (the extent to which use of these products may lead to persistent and/or problematic use). In this study, 24 experienced male e-cig users completed 4 sessions that differed byproduct used: own e-cig (OWN), an eGo e-cig filled with participants' own brand/flavor liquid in 0 mg/mL nicotine (e-cig0), an eGo e-cig filled with the highest nicotine concentration available in participants' own brand/flavor (e-cighighest), and a U.S. Food and Drug Administration-approved nicotine inhaler (IN). Outcome measures included crossover point on the multiple-choice procedure, plasma nicotine delivery, and subjective effect profile. After 10 puffs, a significantly higher mean crossover point was observed for OWN at $1.35 (SD = 0.90) compared to e-cighighest at $0.88 (SD = 0.89), e-cig0 at $0.83 (SD = 0.79), and IN at $0.72 (SD = 0.84). Significant increases in mean plasma nicotine concentration were observed for OWN at 7.94 ng/mL (SD = 6.19) and e-cighighest at 7.51 ng/mL (SD = 5.39). Significant reductions in abstinence symptom suppression and higher ratings of satisfaction were observed for OWN and e-cighighest, with significantly less suppression and lower ratings of satisfaction for e-cig0 and IN. These findings suggest that human laboratory methods can be used to assess e-cig abuse liability and that nicotine-containing e-cigs have greater abuse liability than nicotine-free e-cigs and the IN. Potential regulations intended to limit e-cig abuse liability should be tested using these or similar procedures. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Under certain conditions, electronic cigarettes (e-cigs) can deliver nicotine to and suppress tobacco abstinence symptoms in cigarette smokers. Growing popularity of e-cigs raises abuse liability concerns. This study's purpose was to compare the abuse liability of an e-cig (1.5 Ohm, 3.3 V) filled with 36 mg/mL or 0 mg/mL nicotine to an Food and Drug Administration (FDA)-approved nicotine inhaler (IN) and participants' own brand (OB) of cigarettes. Smokers (N = 24) completed four sessions in which they completed the multiple-choice procedure, and plasma nicotine concentration and subjective effects were measured. Mean (SD) multiple-choice procedure crossover point was $0.87 (1.0) for the 36-mg/mL nicotine e-cig and $0.96 (1.2) for the 0-mg/mL e-cig, significantly higher than the IN mean of $0.32 (0.6) but significantly lower than the OB cigarette mean of $1.42 (1.4). Ten puffs from an own-brand cigarette increased mean plasma nicotine concentration from 3.55 (2.8) to 13.64 (9.8) ng/mL, as compared to an increase from 3.16 (1.8) to 8.51 (5.4) ng/mL for the 36-mg/mL e-cig. The 36-mg/mL e-cig reduced nicotine abstinence symptoms more than the 0-mg/mL e-cig, and both e-cigs were rated as more reinforcing than the inhaler but less reinforcing than participants' OB cigarettes (ps < .05). Results suggest that the e-cig examined had higher abuse liability than the IN but lower than combustible cigarettes. These data and methods may be useful for policymakers by revealing how e-cig abuse liability compares to tobacco/nicotine products with abuse liability profiles that are well established. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Waterpipe tobacco smoking (WTS) exposes users to toxicants in much greater amounts than a cigarette. Little is known about how gender affects WTS toxicant exposure and subjective response. Data from three WTS clinical laboratory studies were combined for analysis. Participants ( N = 99; 38 women) completed a 45-min WTS session where they smoked a waterpipe ad libitum. Puff topography was measured throughout, and plasma nicotine concentration, expired air carbon monoxide (CO), and subjective responses were measured pre- and post-WTS. There was a gender effect for total puff volume with men inhaling a greater smoke volume, on average ( M = 59.9 L, SD = 40.7), compared with women ( M = 38.8 L, SD = 27.8; p < .01). Men had greater post-WTS mean plasma nicotine concentrations ( M = 10.0 ng/ml, SD = 7.1) compared with women ( M = 6.9 ng/ml, SD = 5.2; p < .05). Post-WTS expired air CO was not associated with gender (men M = 27.6 ppm, SD = 18.9; women M = 22.7 ppm, SD = 17.0, ns ). Relative to men, women had higher post-WTS scores for subjective measures of "nauseous," "dizzy," "nervous," "headache," and "heart pounding." Men and women are exposed to toxicants during WTS, and men may achieve higher nicotine exposure than women, likely resulting from differences in smoke inhaled. However, similar post-WTS expired air CO between men and women and higher ratings of negative subjective responses among women may indicate that factors beyond puff topography may impact toxicant exposure and subjective response to WTS. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Electronic cigarette (ECIG) nicotine delivery and other effects may depend on liquid nicotine concentration and user experience. This study is the first to systematically examine the influence of ECIG liquid nicotine concentration and user experience on nicotine delivery, heart rate, puff topography, and subjective effects. Thirty-three ECIG-experienced individuals and 31 ECIG-naïve cigarette smokers completed 4 laboratory conditions consisting of 2, 10-puff bouts (30-sec interpuff interval) with a 3.3-V ECIG battery attached to a 1.5-Ω "cartomizer" (7.3 W) filled with 1 ml ECIG liquid. Conditions differed by liquid nicotine concentration: 0, 8, 18, or 36 mg/ml. Participants' plasma nicotine concentration was directly related to liquid nicotine concentration and dependent on user experience, with significantly higher mean plasma nicotine increases observed in ECIG-experienced individuals relative to ECIG-naïve smokers in each active nicotine condition. When using 36 mg/ml, mean plasma nicotine increase for ECIG-experienced individuals was 17.9 ng/ml (SD = 17.2) and 6.9 (SD = 7.1; p < .05) for ECIG-naïve individuals. Between-group differences were likely due to longer puffs taken by experienced ECIG users: collapsed across condition, mean puff duration was 5.6 sec (SD = 3.0) for ECIG-experienced and 2.9 (SD = 1.5) for ECIG-naïve individuals. ECIG use also suppressed nicotine/tobacco abstinence symptoms in both groups; the magnitude of abstinence symptom suppression depended on liquid nicotine concentration and user experience. These and other recent results suggest that policies intended to limit ECIG nicotine delivery will need to account for factors in addition to liquid nicotine concentration (e.g., device power and user behavior). (PsycINFO Database Record, ((c) 2017 APA, all rights reserved).)

Electronic cigarettes (ECIGs) use electricity to power a heating element that aerosolizes a liquid containing solvents, flavorants, and the dependence-producing drug nicotine for user inhalation. ECIGs have evolved rapidly in the past 8 years, and the changes in product design and liquid constituents affect the resulting toxicant yield in the aerosol and delivery to the user. This rapid evolution has been accompanied by dramatic increases in ECIG use prevalence in many countries among adults and, especially, adolescents in the United States. The increased prevalence of ECIGs that deliver nicotine and other toxicants to users' lungs drives a rapidly growing research effort. This review highlights the most recent information regarding the design of ECIGs and their liquid and aerosol constituents, the epidemiology of ECIG use among adolescents and adults (including correlates of ECIG use), and preclinical and clinical research regarding ECIG effects. The current literature suggests a strong rationale for an empirical regulatory approach toward ECIGs that balances any potential ECIG-mediated decreases in health risks for smokers who use them as substitutes for tobacco cigarettes against any increased risks for nonsmokers who may be attracted to them., (© 2016 New York Academy of Sciences.)

Objective: Evaluating electronic cigarettes (ECIGs) in the clinical laboratory is critical to understanding their effects. However, laboratory evaluation of ECIGs can be challenging, as they are a novel, varied, and evolving class of products. The objective of this paper is to describe some methodological challenges to the clinical laboratory evaluation of ECIGs., Methods: The authors gathered information about challenges involved in the laboratory evaluation of ECIGs. Challenges were categorized and solutions provided when possible., Results: Methods used to study combustible cigarettes may need to be adapted to account for ECIG novelty and differences within the class. Challenges to ECIG evaluation can include issues related to 1) identification of ECIG devices and liquids, 2) determination of short -term ECIG abstinence, 3) measurement of use behavior, and 4) assessment of dependence. These challenges are discussed, and some suggestions to inform ECIG evaluation using clinical laboratory methods are provided., Conclusions: Awareness of challenges and developing, validating, and reporting methods used to address them aids interpretation of results and replication efforts, thus enhancing the rigor of science used to protect public health through appropriate, empirically-based, ECIG regulation., Competing Interests: Conflict of InterestStatement All authors of this article declare they have no conflicts of interest.

Background: While dopamine signaling in the nucleus accumbens (NAc) plays a well-established role in motivating cocaine use in early nonaddicted stages, recent evidence suggests that other signaling pathways may be critical once addiction has developed. Given the importance of glutamatergic signaling in the NAc for drug seeking and relapse, here we examined its role in motivating cocaine self-administration under conditions known to produce either a nonaddicted or an addicted phenotype., Methods: Following acquisition, male and female Sprague Dawley rats were given either short access (three fixed-ratio 1 sessions, 20 infusions/day) or extended 24-hour access (10 days; 4 trials/hour; up to 96 infusions/day) to cocaine. Following a 14-day abstinence period, motivation for cocaine was assessed under a progressive-ratio schedule, and once stable, the effects of intra-NAc infusions of the glutamate alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate/kainate receptor antagonist CNQX (0, .01, .03, .1 μg/side) were determined. As an additional measure for the development of an addicted phenotype, separate groups of rats were screened under an extinction/cue-induced reinstatement procedure following abstinence from short-access versus extended-access self-administration., Results: Motivation for cocaine and levels of extinction and reinstatement responding were markedly higher following extended-access versus short-access self-administration, confirming the development of an addicted phenotype in the extended-access group. CNQX dose-dependently reduced motivation for cocaine in the extended-access group but was without effect in the short-access group., Conclusions: These results suggest that the role of glutamatergic signaling in the NAc, though not essential for motivating cocaine use in nonaddicted stages, becomes critical once addiction has developed., (Published by Elsevier Inc.)