Effects of Electronic Cigarette Liquid Nicotine Concentration on Plasma Nicotine and Puff Topography in Tobacco Cigarette Smokers: A Preliminary Report

The Importance of Conditioned Stimuli in Cigarette and E-Cigarette Craving Reduction by E-Cigarettes

This study examined the impact of four variables pertaining to the use of e-cigarettes (e-cigs) on cravings for tobacco cigarettes and for e-cigs after an overnight abstinence period. The four variables were the nicotine level, the sensorimotor component, the visual aspect, and the aroma of the e-cig. In an experimental study, 81 participants without prior vaping experience first got acquainted with using e-cigs in a one-week tryout period, after which they participated in a lab session assessing the effect of five minutes of vaping following an abstinence period of 12 h. A mixed-effects model clearly showed the importance of nicotine in craving reduction. However, also non-nicotine factors, in particular the sensorimotor component, were shown to contribute to craving reduction. Handling cues interacted with the level (presence/absence) of nicotine: it was only when the standard hand-to-mouth action cues were omitted that the craving reducing effects of nicotine were observed. Effects of aroma or visual cues were not observed, or weak and difficult to interpret, respectively.

Overview of Electronic Nicotine Delivery Systems: A Systematic Review

CONTEXT

Rapid developments in e-cigarettes, or electronic nicotine delivery systems (ENDS), and the evolution of the overall tobacco product marketplace warrant frequent evaluation of the published literature. The purpose of this article is to report updated findings from a comprehensive review of the published scientific literature on ENDS.

EVIDENCE ACQUISITION

The authors conducted a systematic review of published empirical research literature on ENDS through May 31, 2016, using a detailed search strategy in the PubMed electronic database, expert review, and additional targeted searches. Included studies presented empirical findings and were coded to at least one of nine topics: (1) Product Features; (2) Health Effects; (3) Consumer Perceptions; (4) Patterns of Use; (5) Potential to Induce Dependence; (6) Smoking Cessation; (7) Marketing and Communication; (8) Sales; and (9) Policies; reviews and commentaries were excluded. Data from included studies were extracted by multiple coders (October 2015 to August 2016) into a standardized form and synthesized qualitatively by topic.

EVIDENCE SYNTHESIS

There were 687 articles included in this systematic review. The majority of studies assessed patterns of ENDS use and consumer perceptions of ENDS, followed by studies examining health effects of vaping and product features.

CONCLUSIONS

Studies indicate that ENDS are increasing in use, particularly among current smokers, pose substantially less harm to smokers than cigarettes, are being used to reduce/quit smoking, and are widely available. More longitudinal studies and controlled trials are needed to evaluate the impact of ENDS on population-level tobacco use and determine the health effects of longer-term vaping.

Nicotine delivery to users from cigarettes and from different types of e-cigarettes

BACKGROUND

Delivering nicotine in the way smokers seek is likely to be the key factor in e-cigarette (EC) success in replacing cigarettes. We examined to what degree different types of EC mimic nicotine intake from cigarettes.

METHODS

Twelve participants ('dual users' of EC and cigarettes) used their own brand cigarette and nine different EC brands. Blood samples were taken at baseline and at 2-min intervals for 10 min and again at 30 min.

RESULTS

Eleven smokers provided usable data. None of the EC matched cigarettes in nicotine delivery (C _max = 17.9 ng/ml, T _max = 4 min and AUC_0->30 = 315 ng/ml/min). The EC with 48 mg/ml nicotine generated the closest PK profile (C _max = 13.6 ng/ml, T _max = 4 min, AUC_0->30 = 245 ng/ml/min), followed by a third generation EC using 20 mg/ml nicotine (C _max = 11.9 ng/ml, T _max = 6 min, AUC_0->30 = 232 ng/ml/min), followed by the tank system using 20 mg/ml nicotine (C _max = 9.9 ng/ml, T _max = 6 min, AUC_0->30 = 201 ng/ml/min). Cig-a-like PK values were similar, ranging from C _max 7.5 to 9.7 ng/ml, T _max 4-6 min, and AUC_0->30 144 to 173 ng/ml/min. Moderate differences in e-liquid nicotine concentrations had little effect on nicotine delivery, e.g. the EC with 24 mg/ml cartridge had the same PK profile as ECs with 16 mg/ml cartridges. Using similar strength e-liquid, the tank EC provided significantly more nicotine than cig-a-like ECs.

CONCLUSIONS

EC brands we tested do not deliver nicotine as efficiently as cigarettes, but newer EC products deliver nicotine more efficiently than cig-a-like brands. Moderate variations in nicotine content of e-liquid have little effect on nicotine delivery. Smokers who are finding cig-a-like EC unsatisfactory should be advised to try more advanced systems.

Reduced nicotine content cigarettes and use of alternative nicotine products: exploratory trial

AIMS

To compare the use of alternative nicotine products, smoking behavior and tobacco biomarker exposure in smokers unwilling to quit who were assigned randomly to normal nicotine content (NNC) cigarettes or very low nicotine content (VLNC) cigarettes.

DESIGN

Randomized, parallel-arm 8-week study with assignment to VLNC (VLNC 1, n = 53) or NNC (NNC, n = 27) with access to non-cigarette combusted and non-combusted tobacco/nicotine products or to VLNC with access to only non-combusted products (VLNC2, n = 56).

SETTING

Clinics in Minnesota, USA.

PARTICIPANTS

Smokers uninterested in quitting smoking with a mean [± standard deviation (SD)] age of 44 (± 14) years and smoking 16 (± seven) cigarettes/day; 51% female, 72% white.

MEASUREMENTS

During the experimental period, the measures taken included: rate of alternative products used, amount of and abstinence from combusted tobacco used and tobacco exposure biomarkers.

FINDINGS

There were higher rates of non-combusted alternative tobacco/nicotine product use in both VLNC conditions versus the NNC condition [rate ratio (RR) = 2.18, 95% confidence interval (CI) = 1.94, 2.46 and RR = 1.64, 95% CI = 1.46, 1.85, respectively] and in VLNC1 versus VLNC2 condition (RR = 1.33, 95% CI = 1.23, 1.44), accompanied by reduced biomarkers of exposure primarily in VLNC2 condition compared to NNC condition (Ps < 0.05). Fewer combusted products were smoked at almost all visits (Ps ≤ 0.02) and there were higher rates of abstinence for both VLNC conditions compared with the NNC condition (VLNC1 versus NNC: RR = 9.96, 95% CI = 5.01, 19.81; VLNC2 versus NNC: RR = 11.23, 95% CI = 5.74, 21.97).

CONCLUSION

The offer of, and instructions to use, reduced nicotine content cigarettes during an 8-week period led to greater use of alternative tobacco/nicotine products compared with continued use of normal nicotine cigarettes and also reductions in smoking rates.

Expanding clinical laboratory tobacco product evaluation methods to loose-leaf tobacco vaporizers

BACKGROUND

Novel tobacco products entering the US market include electronic cigarettes (ECIGs) and products advertised to "heat, not burn" tobacco. There is a growing literature regarding the acute effects of ECIGs. Less is known about "heat, not burn" products. This study's purpose was to expand existing clinical laboratory methods to examine, in cigarette smokers, the acute effects of a "heat, not burn" "loose-leaf tobacco vaporizer" (LLTV).

METHODS

Plasma nicotine and breath carbon monoxide (CO) concentration and tobacco abstinence symptom severity were measured before and after two 10-puff (30-s interpuff interval) product use bouts separated by 60min. LLTV effects were compared to participants' own brand (OB) cigarettes and an ECIG (3.3V; 1.5ohm; 18mg/ml nicotine).

RESULTS

Relative to OB, LLTV increased plasma nicotine concentration to a lesser degree, did not increase CO, and did not appear to reduce abstinence symptoms as effectively. Relative to ECIG, LLTV nicotine and CO delivery and abstinence symptom suppression did not differ. Participants reported that both the LLTV and ECIG were significantly less satisfying than OB.

CONCLUSIONS

Results demonstrate that LLTVs are capable of delivering nicotine and suppressing tobacco abstinence symptoms partially; acute effects of these products can be evaluated using existing clinical laboratory methods. Results can inform tobacco product regulation and may be predictive of the extent that these products have the potential to benefit or harm overall public health.

Week Long Topography Study of Young Adults Using Electronic Cigarettes in Their Natural Environment

Results of an observational, descriptive study quantifying topography characteristics of twenty first generation electronic nicotine delivery system users in their natural environment for a one week observation period are presented. The study quantifies inter-participant variation in puffing topography between users and the intra-participant variation for each user observed during one week of use in their natural environment. Puff topography characteristics presented for each user include mean puff duration, flow rate and volume for each participant, along with descriptive statistics of each quantity. Exposure characteristics including the number of vaping sessions, total number of puffs and cumulative volume of aerosol generated from ENDS use (e-liquid aerosol) are reported for each participant for a one week exposure period and an effective daily average exposure. Significant inter-participant and intra-participant variation in puff topography was observed. The observed range of natural use environment characteristics is used to propose a set of topography protocols for use as command inputs to drive machine-puffed electronic nicotine delivery systems in a controlled laboratory environment.

Have combustible cigarettes met their match? The nicotine delivery profiles and harmful constituent exposures of second-generation and third-generation electronic cigarette users

INTRODUCTION

Electronic cigarettes' (e-cigarettes) viability as a public health strategy to end smoking will likely be determined by their ability to mimic the pharmacokinetic profile of a cigarette while also exposing users to significantly lower levels of harmful/potentially harmful constituents (HPHCs). The present study examined the nicotine delivery profile of third- (G3) versus second-generation (G2) e-cigarette devices and their users' exposure to nicotine and select HPHCs compared with cigarette smokers.

METHODS

30 participants (10 smokers, 9 G2 and 11 G3 users) completed baseline questionnaires and provided exhaled carbon monoxide (eCO), saliva and urine samples. Following a 12-hour nicotine abstinence, G2 and G3 users completed a 2-hour vaping session (ie, 5 min, 10-puff bout followed by ad libitum puffing for 115 min). Blood samples, subjective effects, device characteristics and e-liquid consumption were assessed.

RESULTS

Smokers, G2 and G3 users had similar baseline levels of cotinine, but smokers had 4 and 7 times higher levels of eCO (p<0.0001) and total 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (i.e., NNAL, p<0.01), respectively, than G2 or G3 users. Compared with G2s, G3 devices delivered significantly higher power to the atomiser, but G3 users vaped e-cigarette liquids with significantly lower nicotine concentrations. During the vaping session, G3 users achieved significantly higher plasma nicotine concentrations than G2 users following the first 10 puffs (17.5 vs 7.3 ng/mL, respectively) and at 25 and 40 min of ad libitum use. G3 users consumed significantly more e-liquid than G2 users. Vaping urges/withdrawal were reduced following 10 puffs, with no significant differences between device groups.

DISCUSSION

Under normal use conditions, both G2 and G3 devices deliver cigarette-like amounts of nicotine, but G3 devices matched the amount and speed of nicotine delivery of a conventional cigarette. Compared with cigarettes, G2 and G3 e-cigarettes resulted in significantly lower levels of exposure to a potent lung carcinogen and cardiovascular toxicant. These findings have significant implications for understanding the addiction potential of these devices and their viability/suitability as aids to smoking cessation.

Clinical Laboratory Evaluation of Electronic Cigarettes/Electronic Nicotine Delivery Systems: Methodological Challenges

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.

Reasons for using flavored liquids among electronic cigarette users: A concept mapping study

BACKGROUND

Electronic cigarettes (ECIGs) aerosolize liquids often containing flavorants for inhalation. Few studies have examined the role of flavors in ECIG use. This study's purpose was to examine reasons for flavored ECIG use using a mixed-method approach, concept mapping (CM).

METHODS

Forty-six past 30-day adult ECIG users recruited from vape forums/conferences completed three online CM tasks. Participants brainstormed responses to a prompt: "A specific reason I use flavored e-liquid in my electronic cigarette product is…". The final 107 brainstormed statements were sorted by participants into groups of similar content. Participants rated each statement on a 7-point scale (1-Definitely NOT a reason to 7-Definitely a reason) based on a prompt: "This is a specific reason why I used flavored e-liquid in my electronic cigarette product in the past month." A cluster map was generated from participants' sorting and ratings using CM statistical software. Cluster mean ratings were compared.

RESULTS

Analysis revealed five clusters of reasons for flavored ECIG use including Increased Satisfaction/Enjoyment, Better Feel/Taste than Cigarettes, Variety/Customization, Food Craving Suppression, and Social Impacts. Statements in the Increased Satisfaction/Enjoyment and Better Feel/Taste than Cigarettes clusters were rated significantly higher than statements from other clusters (ps<0.05). Some statements indicated flavors were perceived as masking agents for nicotine or other bad tastes associated with cigarette smoking making ECIG use more palatable.

CONCLUSIONS

Flavored ECIGs are used for many reasons. Some statements suggested flavors may increase the rewarding and possible addictive effects of ECIGs. These results support continued examination of the role of flavors and ECIG use behaviors.

A transdisciplinary model to inform randomized clinical trial methods for electronic cigarette evaluation

BACKGROUND

This study is a systematic evaluation of a novel tobacco product, electronic cigarettes (ECIGs) using a two-site, four-arm, 6-month, parallel-group randomized controlled trial (RCT) with a follow-up to 9 months. Virginia Commonwealth University is the primary site and Penn State University is the secondary site. This RCT design is important because it is informed by analytical work, clinical laboratory results, and qualitative/quantitative findings regarding the specific ECIG products used.

METHODS

Participants (N = 520) will be randomized across sites and must be healthy smokers of >9 cigarettes for at least one year, who have not had a quit attempt in the prior month, are not planning to quit in the next 6 months, and are interested in reducing cigarette intake. Participants will be randomized into one of four 24-week conditions: a cigarette substitute that does not produce an inhalable aerosol; or one of three ECIG conditions that differ by nicotine concentration 0, 8, or 36 mg/ml. Blocked randomization will be accomplished with a 1:1:1:1 ratio of condition assignments at each site. Specific aims are to: characterize ECIG influence on toxicants, biomarkers, health indicators, and disease risk; determine tobacco abstinence symptom and adverse event profile associated with real-world ECIG use; and examine the influence of ECIG use on conventional tobacco product use. Liquid nicotine concentration-related differences on these study outcomes are predicted. Participants and research staff in contact with participants will be blinded to the nicotine concentration in the ECIG conditions.

DISCUSSION

Results from this study will inform knowledge concerning ECIG use as well as demonstrate a model that may be applied to other novel tobacco products. The model of using prior empirical testing of ECIG devices should be considered in other RCT evaluations.

TRIAL REGISTRATION

TRN: NCT02342795 , registered December 16, 2014.

Effects of Electronic Cigarette Liquid Nicotine Concentration on Plasma Nicotine and Puff Topography in Tobacco Cigarette Smokers: A Preliminary Report

INTRODUCTION

Electronic cigarettes (ECIGs) aerosolize a liquid that usually contains propylene glycol and/or vegetable glycerin, flavorants, and the dependence-producing drug nicotine in various concentrations. This study examined the extent to which ECIG liquid nicotine concentration is related to user plasma nicotine concentration in ECIG-naïve tobacco cigarette smokers.

METHODS

Sixteen ECIG-naïve cigarette smokers completed four laboratory sessions that differed by the nicotine concentration of the liquid (0, 8, 18, or 36 mg/ml) that was placed into a 1.5 Ohm, dual coil "cartomizer" powered by a 3.3V battery. In each session, participants completed two, 10-puff ECIG use bouts with a 30-second inter-puff interval; bouts were separated by 60 minutes. Venous blood was sampled before and after bouts for later analysis of plasma nicotine concentration; puff duration, volume, and average flow rate were measured during each bout.

RESULTS

In bout 1, relative to the 0mg/ml nicotine condition (mean = 3.8 ng/ml, SD = 3.3), plasma nicotine concentration increased significantly immediately after the bout for the 8 (mean = 8.8 ng/ml, SD = 6.3), 18 (mean = 13.2 ng/ml, SD = 13.2), and 36 mg/ml (mean = 17.0 ng/ml, SD = 17.9) liquid concentration. A similar pattern was observed after bout 2. Average puff duration in the 36 mg/ml condition was significantly shorter compared to the 0mg/ml nicotine condition. Puff volume increased during the second bout for 8 and 18 mg/ml conditions.

CONCLUSIONS

For a given ECIG device, nicotine delivery may be directly related to liquid concentration. ECIG-naïve cigarette smokers can, from their first use bout, attain cigarette-like nicotine delivery profiles with some currently available ECIG products.

IMPLICATIONS

Liquid nicotine concentration can influence plasma nicotine concentration in ECIG-naïve cigarette smokers, and, at some concentrations, the nicotine delivery profile of a 3.3V ECIG with a dual coil, 1.5-Ohm cartomizer approaches that of a combustible tobacco cigarette in this population. Finding a product that delivers nicotine as effectively as a tobacco cigarette, as we report here, may be essential for smokers who want to replace completely their combustible tobacco cigarettes with ECIGs.

Electronic cigarette nicotine delivery can exceed that of combustible cigarettes: a preliminary report

INTRODUCTION

Electronic cigarettes (ECIGs) aerosolise a liquid that usually contains propylene glycol and/or vegetable glycerine, flavourants and the dependence-producing drug, nicotine, in various concentrations. This laboratory study examined the relationship between liquid nicotine concentration and plasma nicotine concentration and puffing behaviour in experienced ECIG users.

METHODS

Sixteen ECIG-experienced participants used a 3.3-Volt ECIG battery attached to a 1.5-Ohm dual-coil 'cartomiser' loaded with 1 mL of a flavoured propylene glycol/vegetable glycerine liquid to complete four sessions, at least 2 days apart, that differed by nicotine concentration (0, 8, 18 or 36 mg/mL). In each session, participants completed two 10-puff ECIG-use bouts (30 s puff interval) separated by 60 min. Venous blood was sampled to determine plasma nicotine concentration. Puff duration, volume and average flow rate were measured.

RESULTS

Immediately after bout 1, mean plasma nicotine concentration was 5.5 ng/mL (SD=7.7) for 0 mg/mL liquid, with significantly (p<0.05) higher mean concentrations observed for the 8 (mean=17.8 ng/mL, SD=14.6), 18 (mean=25.9 ng/mL, SD=17.5) and 36 mg/mL (mean=30.2 ng/mL; SD=20.0) concentrations; a similar pattern was observed for bout 2. For bout 1, at 36 mg/mL, the mean post- minus pre-bout difference was 24.1 ng/mL (SD=18.3). Puff topography data were consistent with previous results and revealed few reliable differences across conditions.

DISCUSSION

This study demonstrates a relationship between ECIG liquid nicotine concentration and user plasma nicotine concentration in experienced ECIG users. Nicotine delivery from some ECIGs may exceed that of a combustible cigarette. The rationale for this higher level of nicotine delivery is uncertain.