ObjectiveTo review the available literature evaluating electronic cigarette (e-cigarette) nicotine clinical pharmacology in order to understand the potential impact of e-cigarettes on individual users, nicotine dependence and public health.MethodsLiterature searches were conducted between 1 October 2012 and 30 September 2013 using key terms in five electronic databases. Studies were included in the review if they were in English and publicly available; non-clinical studies, conference abstracts and studies exclusively measuring nicotine content in e-cigarette cartridges were excluded from the review.ResultsNicotine yields from automated smoking machines suggest that e-cigarettes deliver less nicotine per puff than traditional cigarettes, and clinical studies indicate that e-cigarettes deliver only modest nicotine concentrations to the inexperienced e-cigarette user. However, current e-cigarette smokers are able to achieve systemic nicotine and/or cotinine concentrations similar to those produced from traditional cigarettes. Therefore, user experience is critically important for nicotine exposure, and may contribute to the products’ ability to support and maintain nicotine dependence.ConclusionsKnowledge about e-cigarette nicotine pharmacology remains limited. Because a user's e-cigarette experience may significantly impact nicotine delivery, future nicotine pharmacokinetic and pharmacodynamic studies should be conducted in experienced users to accurately assess the products’ impact on public health.

Background A growing body of evidence suggests that tobacco dependence symptoms can occur soon after smoking onset and with low levels of use. However, limited data are available nationally and among non-cigarette tobacco users. Purpose To examine the prevalence and determinants of tobacco dependence symptoms among adolescent tobacco users in the 2012 National Youth Tobacco Survey, a nationally representative, school-based survey of U.S. middle and high school students. Methods Multivariate logistic regression was used to identify independent predictors of dependence symptoms among current users (i.e., past 30-day use) of cigarettes, cigars, or smokeless tobacco. Analyses were conducted in 2013 using SAS-callable SUDAAN, version 11 to account for the complex survey design. Results Prevalence of tobacco dependence symptoms ranged from 20.8% (95% CI=18.6, 23.1) of current tobacco users reporting wanting to use tobacco within 30 minutes of waking to 41.9% (95% CI=39.3, 44.5) reporting recent strong cravings. Reporting of dependence symptoms was most consistently associated with polytobacco use, higher frequency of use, earlier initiation age, and female gender. A 2–4-fold increase in the odds of symptom reporting was found in adolescents using tobacco products on as few as 3–5 days compared to those who only used it for 1–2 of the past 30 days. Conclusions A substantial proportion of U.S. adolescent tobacco users, including those with low levels of use, report symptoms of tobacco dependence. These findings demonstrate the need for full implementation of evidence-based strategies to prevent both experimentation and progression to regular tobacco use among youth.

BackgroundCigar and e-cigarette use is becoming increasingly common among US tobacco users and the Food and Drug Administration recently asserted regulatory jurisdiction over these products, among others, in May 2016. Research on tobacco dependence among users of these products is limited, however. We therefore examined several symptoms of dependence and cessation intentions among adult cigarette, cigar, and/or e-cigarette users in a nationally representative sample.MethodsWe used nationally representative data from more than 60,000 participants in the US National Adult Tobacco Survey (NATS) from 2012 to 2013 to analyze dependence symptoms and cessation intentions for users of cigarettes, cigars, and/or e-cigarettes but not other tobacco products.ResultsAmong daily tobacco users, dual cigarette and cigar users on average smoked more cigarettes per day (17.3, 95 % CI = 16.1, 18.6 vs. 15.8, 95 % CI = 15.4, 16.2), had shorter times to first tobacco use after waking (21.4 min, 95 % CI = 16.6, 24.9 vs. 25.9 min, 95 % CI = 25.3, 26.5), and were more likely to report withdrawal and craving symptoms than exclusive cigarette smokers. Dual cigarette and e-cigarette users were more likely than exclusive cigarette smokers to report withdrawal and craving symptoms and cessation intentions. Exclusive cigar and e-cigarette users were less likely to report withdrawal and craving symptoms than users of other products, but even so, more than a third of exclusive cigar (38.8 %, 95 % CI = 27.4 %, 51.6 %) and e-cigarette (46.1 %, 95 % CI = 35.1 %, 57.4 %) users reported experiencing a strong craving for a tobacco product in the past 30 days.ConclusionsDual cigarette and cigar users show evidence of greater dependence symptoms and dual cigarette and e-cigarette users show evidence of greater dependence symptoms and cessation intentions compared with exclusive cigarette smokers. A sizeable number of users of all of the tobacco products report dependence symptoms such as craving for tobacco.

Introduction Concurrent use of cigarettes and smokeless tobacco is common, but little is known regarding the association of smokeless tobacco use with cigarette smoking cessation. Dual users may have lower cigarette consumption levels, which may also play a role in smoking cessation. Methods The 2010–2011 Tobacco Use Supplement to the Current Population Survey included 26,760 current cigarette smokers, of which 675 concurrently used smokeless tobacco. We compared characteristics of the most recent cigarette smoking quit attempt of the past year between dual users and exclusive smokers, using multivariate regression. Results Dual users (45%) were more likely than exclusive smokers (37%) to have made a cigarette smoking quit attempt during the previous year (p<0.01), even after adjusting for demographic differences and cigarette dependence levels (ORadj 1.33, 95% CI 1.15–1.53). Half (48%) of dual users who made a quit attempt tried to quit “by switching to smokeless tobacco”. However, once in a quit attempt, dual users relapsed more quickly than exclusive smokers (Cox regression HRadj 1.13, 95% CI 1.02–1.26). There was no difference in 30-day abstinence rates on the most recent quit attempt (ORadj 1.09, 95% CI 0.88–1.37). For both groups, the best predictor of past 30-day abstinence was cigarette consumption level. Conclusions Current cigarette smokers who also use smokeless tobacco are more likely to have tried to quit, but relapse more quickly than exclusive smokers, and are not more likely to have attained 30 day smoking cessation. Prospective studies at the population level are needed.

Background Previous research indicates that subjects with anterior cruciate ligament reconstruction exhibit abnormal knee joint movement patterns during functional activities like walking. While the sagittal plane mechanics have been studied extensively, less is known about the secondary planes, specifically with regard to more demanding tasks. This study explored the influence of task complexity on functional joint mechanics in the context of graft-specific surgeries. Methods In 25 participants (10 hamstring tendon graft, 6 patellar tendon graft, 9 matched controls), three-dimensional joint torques were calculated using a standard inverse dynamics approach during level walking and stair descent. The stair descent task was separated into two functionally different sub-tasks—step-to-floor and step-to-step. The differences in external knee moment profiles were compared between groups; paired differences between the reconstructed and non-reconstructed knees were also assessed. Findings The reconstructed knees, irrespective of graft type, typically exhibited significantly lower peak knee flexion moments compared to control knees during stair descent, with the differences more pronounced in the step-to-step task. Frontal plane adduction torque deficits were graft-specific and limited to the hamstring tendon knees during the step-to-step task. Internal rotation torque deficits were also primarily limited to the hamstring tendon graft group during stair descent. Collectively, these results suggest that task complexity was a primary driver of differences in joint mechanics between anterior cruciate ligament reconstructed individuals and controls, and such differences were more pronounced in individuals with hamstring tendon grafts. Interpretation The mechanical environment experienced in the cartilage during repetitive, cyclical tasks such as walking and other activities of daily living has been argued to contribute to the development of degenerative changes to the joint and ultimately osteoarthritis. Given the task-specific and graft-specific differences in joint mechanics detected in this study, care should be taken during the rehabilitation process to mitigate these changes.