Plasma Nicotine Research Articles

Effects of user puff topography, device voltage, and liquid nicotine concentration on electronic cigarette nicotine yield: measurements and model predictions.

Some electronic cigarette (ECIG) users attain tobacco cigarette-like plasma nicotine concentrations while others do not. Understanding the factors that influence ECIG aerosol nicotine delivery is relevant to regulation, including product labeling and abuse liability. These factors may include user puff topography, ECIG liquid composition, and ECIG design features. This study addresses how these factors can influence ECIG nicotine yield. Aerosols were machine generated with 1 type of ECIG cartridge (V4L CoolCart) using 5 distinct puff profiles representing a tobacco cigarette smoker (2-s puff duration, 33-ml/s puff velocity), a slow average ECIG user (4 s, 17 ml/s), a fast average user (4 s, 33 ml/s), a slow extreme user (8 s, 17 ml/s), and a fast extreme user (8 s, 33 ml/s). Output voltage (3.3-5.2 V or 3.0-7.5 W) and e-liquid nicotine concentration (18-36 mg/ml labeled concentration) were varied. A theoretical model was also developed to simulate the ECIG aerosol production process and to provide insight into the empirical observations. Nicotine yields from 15 puffs varied by more than 50-fold across conditions. Experienced ECIG user profiles (longer puffs) resulted in higher nicotine yields relative to the tobacco smoker (shorter puffs). Puff velocity had no effect on nicotine yield. Higher nicotine concentration and higher voltages resulted in higher nicotine yields. These results were predicted well by the theoretical model (R (2) = 0.99). Depending on puff conditions and product features, 15 puffs from an ECIG can provide far less or far more nicotine than a single tobacco cigarette. ECIG emissions can be predicted using physical principles, with knowledge of puff topography and a few ECIG device design parameters.

Make your own cigarettes: toxicant exposure, smoking topography, and subjective effects.

Despite considerable use of make your own (MYO) cigarettes worldwide and increasing use in the United States, relatively little is known about how these cigarettes are smoked and the resultant toxicant exposure. In a laboratory study, we compared two types of MYO cigarettes-roll your own (RYO) and personal machine made (PMM)-with factory-made (FM) cigarettes in three groups of smokers who exclusively used RYO (n = 34), PMM (n = 23), or FM (n = 20). Within each group, cigarettes were smoked in three conditions: (i) after confirmed overnight tobacco abstinence; (ii) in an intense smoking paradigm; and (iii) without restrictions. All cigarettes were smoked ad lib through a smoking topography unit. Plasma nicotine significantly increased after cigarettes in all conditions except PMM in the intense smoking paradigm. Puff volume, puff duration, total puff volume, and puff velocity did not differ between cigarette types but the puffs per cigarette and time to smoke were significantly smaller for RYO compared with PMM and FM. Regardless of the cigarette, participants consumed the first three puffs more vigorously than the last three puffs. Despite the belief of many of their consumers, smoking MYO cigarettes is not a safe alternative to FM cigarettes. Like FM, MYO cigarettes expose their users to harmful constituents of tobacco smoke. Despite differences in size and design their puffing profiles are remarkably similar. These data are relevant to health and regulatory considerations on the MYO cigarettes.

Magnitudes of biomarker reductions in response to controlled reductions in cigarettes smoked per day: A one-week clinical confinement study

Tobacco toxicant-related exposure reduction is an important tool in harm reduction. Cigarette per day reduction (CPDR) occurs as smokers migrate from smoking cigarettes to using alternative tobacco/nicotine products, or quit smoking. Few reports characterize the dose-response relationships between CPDR and effects on exposure biomarkers, especially at the low end of CPD exposure (e.g., 5 CPD). We present data on CPDR by characterizing magnitudes of biomarker reductions. We present data from a well-controlled, one-week clinical confinement study in healthy smokers who were switched from smoking 19-25 CPD to smoking 20, 10, 5 or 0 CPD. Biomarkers were measured in blood, plasma, urine, and breath, and included smoke-related toxicants, urine mutagenicity, smoked cigarette filter analyses (mouth level exposure), and vital signs. Many of the biomarkers (e.g., plasma nicotine) showed strong CPDR dose-response reductions, while others (e.g., plasma thiocyanate) showed weaker dose-response reductions. Factors that lead to lower biomarker reductions include non-CPD related contributors to the measured response (e.g., other exposure sources from environment, life style, occupation; inter-individual variability). This study confirms CPDR dose-responsive biomarkers and suggests that a one-week design is appropriate for characterizing exposure reductions when smokers switch from cigarettes to new tobacco products.

Nicotine pharmacokinetics in rats is altered as a function of age, impacting the interpretation of animal model data.

Several behavioral studies report that adolescent rats display a preference for nicotine compared with adults. However, age-related pharmacokinetic differences may confound the interpretation of these findings. Thus, differences in pharmacokinetic analyses of nicotine were investigated. Nicotine was administered via acute s.c. (1.0 mg base/kg) or i.v. (0.2 mg base/kg) injection to early adolescent (EA; postnatal day 25) and adult (AD; postnatal day 71) male Wistar rats. Nicotine and its primary metabolite, cotinine, and additional metabolites nornicotine, nicotine-1'-N-oxide, trans-3'-hydroxycotinine, and norcotinine were sampled from 10 minutes to 8 hours (plasma) and 2 to 8 hours (brain) post nicotine and analyzed by liquid chromatography-tandem mass spectrometry. Following s.c. nicotine, the EA cohort had lower levels of plasma nicotine, cotinine, and nicotine-1'-N-oxide at multiple time points, resulting in a lower area under the plasma concentration-time curve (AUC) for nicotine (P < 0.001), cotinine (P < 0.01), and nicotine-1'-N-oxide (P < 0.001). Brain levels were also lower for these compounds. In contrast, the EA cohort had higher plasma and brain AUCs (P < 0.001) for the minor metabolite nornicotine. Brain-to-plasma ratios varied for nicotine and its metabolites, and by age. Following i.v. nicotine administration, similar age-related differences were observed, and this route allowed detection of a 1.6-fold-larger volume of distribution and 2-fold higher plasma clearance in the EA cohort compared with the AD cohort. Thus, unlike in humans, there are substantial age differences in nicotine pharmacokinetics such that for a given nicotine dose, adolescent rats will have lower plasma and brain nicotine compared with adults, suggesting that this should be considered when interpreting animal model data.

Nicotine causes genotoxic damage but is not metabolized during long-term exposure of human nasal miniorgan cultures

Human nasal miniorgan cultures (MOC) are a useful tool in ecogenotoxicology. Repetitive exposure to nicotine showed reversible DNA damage, and stable CYP2A6 expression was demonstrated in nasal MOC in previous investigations. The aim of the present study was to evaluate the genotoxic effect of nicotine in nasal MOC after chronic nicotine exposure, and to monitor possible metabolism capacities. MOC were dissected from human nasal mucosa and cultured under standard cell culture conditions. MOC were exposed to nicotine for 3 weeks at concentrations of 1μM and 1mM. The concentrations were chosen based on nicotine plasma levels in heavy smokers, and possible concentrations used in topical application of nicotine nasal spray. DNA damage was assessed by the comet assay at days 7, 14 and 21. Concentrations of nicotine and cotinine were analyzed in cell culture medium by gas chromatography/mass spectrometry to determine a possible metabolism of nicotine by MOC. Distinct DNA damage in MOC could be demonstrated after 1 week of exposure to 1μM and 1mM nicotine. This effect decreased after 2 and 3 weeks with no statistically relevant DNA migration. No nicotine metabolism could be detected by changes in nicotine and cotinine concentrations in the supernatants. This is the first time genotoxic effects have been evaluated in nasal MOC after chronic nicotine exposure for up to 3 weeks. Genotoxic effects were present after 1 week of culture with a decrease over time. Down-regulation of nicotinic acetylcholine receptors, which are expressed in nasal mucosa, may be a possible explanation. The lack of nicotine metabolism in this model could be explained by the functional loss of CYP2A6 during chronic nicotine exposure. Further investigations are necessary to provide a more detailed description of the underlying mechanisms involved in DNA damage by nicotine.

Effects of methoxsalen, a CYP2A5/6 inhibitor, on nicotine dependence behaviors in mice

Metabolism of nicotine to inactive cotinine by hepatic enzyme CYP2A6 is the principal pathway by which active nicotine is removed from circulation. We therefore hypothesized that inhibition of mouse CYP2A5, the ortolog of human CYP2A6, by methoxsalen (8-methoxypsoralen) alter dependence-related behaviors of nicotine in the mouse. Conditioned place preference (CPP) test was used to assess the appetitive reward-like properties and precipitated nicotine withdrawal to assess physical (somatic and hyperalgesia) and affective (anxiety-related behaviors) measures. The nicotine plasma levels were also measured with or without methoxsalen pretreatment. Methoxsalen (15 and 30 mg/kg, intraperitoneally) pretreatment enhanced nicotine-induced preference in mice (p < 0.05). However, there was a lack of enhancement of nicotine in the CPP test after the highest dose of the CYP-2A5 inhibitor. Similarly to the CPP results, repeated administration of methoxsalen increased the intensity of mecamylamine-precipitated withdrawal signs. The potentiation of nicotine preference and withdrawal intensity by methoxsalen was accompanied by significant increase in nicotine plasma levels in mice (p < 0.05). Finally, methoxsalen enhanced the ability of a very low dose of nicotine (0.05 mg/kg) to reverse withdrawal signs in mice undergoing spontaneous withdrawal after chronic nicotine infusion (p < 0.05). In conclusion, inhibition of nicotine metabolism by methoxsalen alters the behavioral effects of nicotine in the mouse. Combining CYP2A6 inhibitors with low dose nicotine replacement therapies may have a beneficial role in smoking cessation because it will decrease the drug elimination rate and maintain plasma and brain nicotine levels.

Laboratory and Clinical Acute Effects of Active and Passive Indoor Group Water-Pipe (Narghile) Smoking

Indoor group water-pipe tobacco smoking, commonly referred to as water-pipe smoking (WPS), especially in coffee shops, has gained worldwide popularity. We performed a comprehensive laboratory and clinical evaluation of the acute effects of active and passive indoor group WPS. This comparative study evaluated pre- and post-30-min active and passive indoor group WPS. The outcome parameters were carboxyhemoglobin (COHb), nicotine, and cotinine levels; CBC count; and cardiorespiratory parameters. Exhaled breath condensate (EBC) cytokines and endothelial function (using the EndoPat device [Itamar Medical Ltd]) were measured only in active smokers. Statistical methods used were Student t test, Wilcoxon signed rank test, Fisher exact test, analysis of variance, and Newman-Keuls post hoc test where relevant. Sixty-two volunteers aged 24.9±6.2 years were included; 47 were active smokers, and 15 were passive smokers. COHb level increased postactive WPS (active smokers, 2.0%±2.9% vs 17.6%±8.8%; P<.00001); six subjects (12.7%) had a >25% increase, and two subjects (4.2%) had a >40% increase. Plasma nicotine level increased postactive WPS (active smokers, 1.2±4.3 ng/mL vs 18.8±13.9 ng/mL; P<.0001); plasma cotinine and urinary nicotine and cotinine levels also increased significantly. EBC IL-4, IL-5, IL-10, IL-17, and γ-interferon decreased significantly with postactive smoking; endothelial function did not change. WPS was associated with adverse cardiorespiratory changes. In passive smokers, COHb level increased (0.8%±0.25% vs 1.2%±0.8%, respectively, P=.003) as did respiratory rate. One session of active indoor group WPS resulted in significant increases in COHb and serum nicotine levels (eightfold and 18-fold, respectively) and was associated with adverse cardiorespiratory health effects. The minor effects found in passive smokers suggest that they too may be affected adversely by exposure to WPS. The results call for action to limit the continuing global spread of WPS in coffee shops. ClinicalTrials.gov; No.: NCT1237548; URL: www.clinicaltrials.gov.

Nicotine Blood Levels and Short-term Smoking Reduction with an Electronic Nicotine Delivery System

To evaluate nicotine delivery from the NJOY® King Bold Electronic Nicotine Delivery System (ENDS) and its short-term potential for smoking reduction or cessation. One week of ad libitum use was followed by measurements of plasma nicotine, heart rate, and craving and withdrawal after 12 hours of nicotine abstinence in 25 adult smokers not interested in quitting. After 5 minutes of use, blood nicotine levels increased by a mean of 3.5 ng/mL (p < .001), heart rate increased, and craving was reduced by 55%. Cigarettes per day were reduced by 39% during the test week, and perceptions of use for reduction or cessation were positive. The NJOY® King Bold ENDS delivers nicotine and led to short-term smoking reduction.

Nicotine absorption from electronic cigarette use: comparison between first and new-generation devices

A wide range of electronic cigarette (EC) devices, from small cigarette-like (first-generation) to new-generation high-capacity batteries with electronic circuits that provide high energy to a refillable atomizer, are available for smokers to substitute smoking. Nicotine delivery to the bloodstream is important in determining the addictiveness of ECs, but also their efficacy as smoking substitutes. In this study, plasma nicotine levels were measured in experienced users using a first- vs. new-generation EC device for 1 hour with an 18 mg/ml nicotine-containing liquid. Plasma nicotine levels were higher by 35–72% when using the new- compared to the first-generation device. Compared to smoking one tobacco cigarette, the EC devices and liquid used in this study delivered one-third to one-fourth the amount of nicotine after 5 minutes of use. New-generation EC devices were more efficient in nicotine delivery, but still delivered nicotine much slower compared to tobacco cigarettes. The use of 18 mg/ml nicotine-concentration liquid probably compromises ECs' effectiveness as smoking substitutes; this study supports the need for higher levels of nicotine-containing liquids (approximately 50 mg/ml) in order to deliver nicotine more effectively and approach the nicotine-delivery profile of tobacco cigarettes.

Abstract B16: The effect of e-cigarette exposure on airway epithelial cell gene expression and transformation.

Abstract Lung cancer is the leading cause of cancer-related mortality in the United States. Despite a strong correlation between cigarette smoking and the onset of lung cancer, the prevalence of smoking still remains high. Strategies to eliminate cigarette smoking have led to the emergence of new tobacco-related products as alternatives for cigarette smoking or tools for smoking cessation. The electronic cigarette (ECIG) is a battery-powered electronic nicotine delivery system (ENDS) designed to deliver nicotine without combusting tobacco. Since nicotine is widely considered the addictive component in tobacco with limited ability to initiate cancer, ECIGs have been advertised to be a safer alternative to tobacco cigarettes (TCIGs). However, the toxicity and potential carcinogenicity of ECIGs have not previously been evaluated. In this study, we assess the impact of ECIG exposure on the carcinogenic potential of immortalized human bronchial epithelial cells on a background of silenced p53 and activated KRAS (H3mut-P53/KRAS). This model is utilized because p53 and KRAS mutations are often observed in the airway of current and former smokers at risk for lung cancer. The epithelial cells were exposed to both a low and high concentration of nicotine in the ECIG vapor- or TCIG smoke-conditioned media. The lower nicotine concentration was selected to mimic the average plasma nicotine levels in ENDS users and did not demonstrate toxic or anti-proliferative effects on the cells. The higher concentration was chosen to represent the anticipated nicotine levels to which the epithelial cells of smokers are actually exposed. In anchorage independent growth assays, the in vitro correlate of malignant transformation, we found enhanced colony growth in the H3mut-P53/KRAS cells following a 10-day treatment with the high nicotine ECIG- and TCIG-conditioned media compared to the untreated and low nicotine treatment groups. We next assessed the effect of ECIG and TCIG exposure on cell invasion using a three-dimensional air-liquid interface (ALI) model. At baseline, H3mut-P53/KRAS cells exhibit invasive behavior in the ALI model, due to the downstream effects of P53 silencing and KRAS activation. Treatment of H3mut-P53/KRAS cells with low nicotine ECIG- and TCIG-conditioned media did not further enhance the degree of invasion observed in the untreated group. We will next examine the effects of high nicotine conditioned media on cell invasion. Finally, gene expression studies show 263 differentially expressed genes following in vitro exposure to ECIG-conditioned media for 96hrs. The high nicotine ECIG-conditioned media induced a gene expression pattern similar to TCIG- conditioned media and whole cigarette smoke exposure in the H3mut-P53/KRAS cells. Preliminary analyses indicate the observed ECIG-specific gene expression changes were concordantly changed following TCIG-conditioned media exposure. We will next compare the ECIG-induced gene expression signature to carcinogenicity-related gene signatures established in previous and ongoing clinical investigations and test ECIG-altered candidate genes for their ability to drive the malignant transformation of airway epithelial cells. These studies will determine the impact of ECIG exposure on lung carcinogenicity and provide needed scientific guidance to the FDA regarding the physiologic effects of ECIGs. These studies were supported by funding from the following: NIH/NCI #U01CA152751 (SMD, TCW), NCI #U01CA152751-S1 (SMD, TCW, SJP), NCI #U01CA152751-AS (SMD, KK), NCI #T32-CA009120-36 (SMD, SJP, PCP), NIH/NHLBI #T32HL072752 (SMD, EL), University of California Tobacco-Related Disease Research Program (TRDRP) #18FT-0060 (TCW), TRDRP #20KT-0055 (TCW), Lung Cancer SPORE P50CA70907 (JDM, JEL) Citation Format: Stacy J. Park, Tonya C. Walser, Catalina Perdomo, Teresa Wang, Paul C. Pagano, Elvira L. Liclican, Kostyantyn Krysan, Jill E. Larsen, John D. Minna, Marc E. Lenburg, Avrum Spira, Steven M. Dubinett. The effect of e-cigarette exposure on airway epithelial cell gene expression and transformation. [abstract]. In: Proceedings of the AACR-IASLC Joint Conference on Molecular Origins of Lung Cancer; 2014 Jan 6-9; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2014;20(2Suppl):Abstract nr B16.

Experimentally Switching from Factory Made to Self-Made Cigarettes: A Preliminary Study of Perceptions, Toxicant Exposure and Smoking Behavior.

There is currently the potential for a great deal of transition and product switching among cigarette smokers. Studies on the transition when cigarette smokers switch from one type of nicotine delivery product to another are needed to understand subsequent toxicant exposure. A preliminary study was performed to determine the feasibility of experimentally replicating the transition from factory made (FM) to personal machine made (PMM) cigarette smoking. The adaptability and perceptions of the consumer and the consequent exposure to cigarette-delivered toxins were assessed. Six adults (4 men) were recruited for four laboratory visits (V1-V4) on study days 1, 5, 10 and 15, respectively. All of the participants agreed to switch from exclusive FM smoking to exclusive PMM cigarette smoking for the duration of the study. Compliance was very high among these participants. Participants progressively accepted the PMM cigarettes and became efficient producers of PMMs as evidenced in the reduced time to make 5 PMMs in the laboratory. Participants reported a preference for FM at visit 2 (V2), but had stated no preference by the fourth visit. Compared to the FMs, the PMMs at V3 (p<0.05) and V4 (p<0.10) had lower CO boost (7.3 vs. 4.1 ppm; p<0.05). Over all conditions, nicotine plasma levels averaged 18.0±2.4 ng/ml before smoking (for both FM and PMM) and 34.0±5.3 ng/mL after smoking; there were no significant differences in the plasma nicotine boost (average 17.7 and 15.4ng/ml after FM and PMM smoking, respectively). Although there were differences between individual subjects' filter butt levels of deposited solanesol the within-subject levels were remarkably similar. Puff topography measures did not vary across visits or cigarette type. Although interpretation of study results must be conservative because of the small sample size, this study demonstrates that experimentally-induced transition from FM to PMM smoking is feasible for laboratory study and the subsequent toxicant exposure is comparable for FM and PMM cigarettes.

Abstract C58: The gene expression and functional impact of E-cigarette exposure on pulmonary epithelial transformation

Abstract Lung cancer is the leading cause of cancer deaths in the United States. Despite a strong correlation between cigarette smoking and the onset of lung cancer, the prevalence of smoking still remains high. Significant reduction or elimination of the use of combustible tobacco products would substantially lower tobacco-caused morbidity and mortality. The electronic cigarette (ECIG) is a battery-powered electronic nicotine delivery system (ENDS) designed to deliver nicotine without combusting tobacco. ECIGs are widely believed to be a safer alternative to tobacco cigarettes (TCIG), however, the toxicity and potential carcinogenicity of ECIGs have not previously been evaluated. In this study, we assess the impact of ECIG exposure on the carcinogenic potential of immortalized human bronchial epithelial cells on a background of silenced p53 and activated KRAS (H3mut-P53/KRAS). This model is utilized because p53 and KRAS mutations are often observed in the airway of current and former smokers at risk for lung cancer. The epithelial cells were exposed to a low and high nicotine concentration of ECIG vapor- or TCIG smoke-conditioned media. The lower nicotine concentration was selected to mimic plasma nicotine levels in ENDS users and did not demonstrate toxic or anti-proliferative effects on the cells. The higher concentration was chosen to represent the anticipated nicotine levels to which the epithelial cells of smokers are actually exposed. In anchorage independent growth assays, the in vitro correlate of malignant transformation, we found enhanced colony growth in the H3mut-P53/KRAS cells following a 10-day treatment with the high nicotine concentration of ECIG- and TCIG-conditioned media compared to the untreated and low nicotine treatment groups. We next assessed the effect of ECIG and TCIG exposure on cell invasion using three-dimensional air-liquid interface (ALI) models. While treatment with the low nicotine concentration of ECIG-conditioned media did not induce invasion-associated morphological changes, cells treated with the low nicotine concentration of TCIG-conditioned media exhibited slightly invasive behavior by breaching the modified basement membrane and invading through the field of fibroblasts/collagen. At baseline, H3mut-P53/KRAS cells exhibit invasive behavior in the ALI model, due to the downstream effects of P53 silencing and KRAS activation. Treatment of H3mut-P53/KRAS cells with the low nicotine concentration of ECIG- and TCIG-conditioned media did not further enhance the degree of invasion observed in the untreated group. We will next examine the effect of the high nicotine concentration on cell invasion. In addition, we are currently evaluating gene expression profiles by microarray of H3mut-P53/KRAS cells exposed to high and low nicotine concentrations of ECIG-conditioned media. This will directly evaluate the impact of ECIGs on carcinogenicity-related gene expression signatures established in previous and ongoing clinical investigations. These studies will determine the impact of ECIG exposure on lung carcinogenicity, which will provide needed scientific guidance to the FDA regarding the physiologic effects of ECIGs. These studies were supported by the NIH/NCI #U01CA152751-S1 (SMD, AS, MEL, TCW) and NIH/NHLBI #T32HL072752 (SJP). Citation Format: Stacy J. Park, Tonya C. Walser, Catalina Perdomo, Paul P. Pagano, Daniel Brass, Elvira L. Liclican, Kostyantyn Krysan, Marc E. Lenburg, Avrum Spira, Steven M. Dubinett. The gene expression and functional impact of E-cigarette exposure on pulmonary epithelial transformation. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr C58.

Escalating Doses of Transdermal Nicotine in Heavy Smokers

Fixed-dose nicotine replacement therapy (NRT) is efficacious for smoking cessation in the general population of smokers. However, it is less effective in populations with psychiatric comorbidities and/or severe tobacco dependence where the percent nicotine replacement is suboptimal. The objective of this pilot study was to determine the effectiveness of nicotine patch dose titration in response to continued smoking in heavily dependent smokers with psychiatric comorbidity. In a single-arm, open-label study adult smokers (mean cigarettes per day, 25.4 ± 13.4; range, 14-43; n = 12) willing to quit were treated with escalating doses of transdermal nicotine and brief counseling intervention if they continued to smoke over a 9-week treatment period. Plasma nicotine and cotinine, along with expired carbon monoxide levels, and the subjective effects of smoking, urge to smoke, demand elasticity, and mood symptoms were also assessed. The mean NRT dose was 32.7 (SD, 16.4) mg/d (range, 7-56 mg/d). Smokers reported significant reductions in both cigarettes per day (mean decrease, 18.4 ± 11.5) confirmed by expired carbon monoxide (mean decrease, 13.5 ± 13.0) with no significant changes in plasma nicotine concentrations during the course of NRT dose titration. There were significant effects on the subjective effects of smoking and measures of smoking behavior. Most commonly reported adverse events were respiratory infections, skin irritation at patch site, nausea, and sleep disturbances, which were generally mild and transient. Titrating doses of NRT to effect with brief intervention hold promise as an effective clinical strategy to assist heavily dependent psychiatrically ill smokers to change their smoking behavior.

Acute electronic cigarette use: nicotine delivery and subjective effects in regular users

Electronic cigarettes are becoming increasingly popular among smokers worldwide. Commonly reported reasons for use include the following: to quit smoking, to avoid relapse, to reduce urge to smoke, or as a perceived lower-risk alternative to smoking. Few studies, however, have explored whether electronic cigarettes (e-cigarettes) deliver measurable levels of nicotine to the blood. This study aims to explore in experienced users the effect of using an 18-mg/ml nicotine first-generation e-cigarette on blood nicotine, tobacco withdrawal symptoms, and urge to smoke. Fourteen regular e-cigarette users (three females), who are abstinent from smoking and e-cigarette use for 12h, each completed a 2.5 h testing session. Blood was sampled, and questionnaires were completed (tobacco-related withdrawal symptoms, urge to smoke, positive and negative subjective effects) at four stages: baseline, 10 puffs, 60min of ad lib use and a 60-min rest period. Complete sets of blood were obtained from seven participants. Plasma nicotine concentration rose significantly from a mean of 0.74ng/ml at baseline to 6.77ng/ml 10min after 10 puffs, reaching a mean maximum of 13.91ng/ml by the end of the ad lib puffing period. Tobacco-related withdrawal symptoms and urge to smoke were significantly reduced; direct positive effects were strongly endorsed, and there was very low reporting of adverse effects. These findings demonstrate reliable blood nicotine delivery after the acute use of this brand/model of e-cigarette in a sample of regular users. Future studies might usefully quantify nicotine delivery in relation to inhalation technique and the relationship with successful smoking cessation/harm reduction.

Genetic and Pharmacokinetic Determinants of Response to Transdermal Nicotine in White, Black, and Asian Nonsmokers

The aim of the study was to examine genetic, pharmacokinetic and demographic factors that influence sensitivity to nicotine in never smokers. Sixty never smokers, balanced for gender and race (Caucasian, Blacks and Asian), wore 7 mg nicotine skin patches for up to 8 hours. Serial plasma nicotine concentrations and subjective and cardiovascular effects were measured, and genetic variation in the CYP2A6 gene, the primary enzyme responsible for nicotine metabolism, was assessed. Nicotine toxicity requiring patch removal developed in 9 subjects and was strongly associated with rate of rise and peak concentrations of plasma nicotine. Toxicity, subjective and cardiovascular effects of nicotine were associated with the presence of reduced function CYP2A6 alleles, presumably reflecting slow nicotine metabolic inactivation. This study has implications for understanding individual differences in responses to nicotine medications, particularly when the latter are used for treating medical conditions in non-smokers, and possibly in vulnerability to developing nicotine dependence.

Good relationship between saliva cotinine kinetics and plasma cotinine kinetics after smoking one cigarette

This study investigated the relationship between plasma and saliva cotinine kinetics after smoking one cigarette and the relationship between cotinine kinetics and estimated nicotine intake, which was calculated as mouth level exposure (MLE) of nicotine, from smoking two test cigarettes with different nicotine yields. This study was conducted in 16 healthy adult Japanese smokers, who did not have null nor reduced-activity alleles of CYP2A6, with a quasi-randomized crossover design of smoking a low-tar cigarette or a high-tar cigarette. Saliva cotinine showed similar concentration profiles to plasma cotinine, and all of the calculated pharmacokinetic parameters of cotinine showed the same values in plasma and saliva. The Cmax and AUC of cotinine showed almost the same dose-responsiveness to the estimated MLE of nicotine between plasma and saliva, but the tmax and t1/2 of cotinine were not affected by the estimated MLE of nicotine in either plasma or saliva. The results show that saliva cotinine kinetics reflects plasma cotinine kinetics, and measurement of saliva cotinine concentration gives the same information as plasma cotinine on the nicotine intake. Thus, saliva cotinine would be a good and less-invasive exposure marker of cigarette smoke, reflecting the plasma cotinine concentration and kinetics.

Pharmacokinetic analysis of nicotine when using non-combustion inhaler type of tobacco product in Japanese adult male smokers

In a clinical study, the pharmacokinetics of nicotine were investigated using the prototype of a non-combustion inhaler type of tobacco product (PNCIT) with comparison to a 1mg tar conventional cigarette (CC). The study was conducted in 12 healthy adult Japanese male smokers with an open-label non-randomized design to make an intra-subject comparison of the use or smoking of these products. Subjects used a single piece of PNCIT with 80 aspirations or smoked a CC with 10 puffs every hour, for a total of 12 PNCITs or CCs on each study day. Under this study regimen, the steady state plasma nicotine concentration was not significantly different between the test tobacco products. The time to reach the maximum plasma nicotine concentration was longer for PNCIT compared to CC, suggesting that nicotine delivered from PNCIT was absorbed primarily in the upper airway, not in the pulmonary sites as cigarette smoking. The relative bioavailability of nicotine for PNCIT compared to CC was 0.92±0.32, indicating similar nicotine bioavailability for both forms. The difference in the elimination half-lives between the test products was not significant, suggesting that the elimination of nicotine from blood is not affected significantly by the difference in the nicotine absorption sites.

Pharmacokinetic and Pharmacodynamics Studies of Nicotine After Oral Administration in Mice: Effects of Methoxsalen, a CYP2A5/6 Inhibitor

The use of novel oral nicotine delivery devices and compositions for human consumption and for animal research studies has been increasing in the last several years. Studies were undertaken to examine whether the systemic administration of methoxsalen, an inhibitor of human CYP2A6 and mouse CYP2A5, would modulate nicotine pharmacokinetics and pharmacological effects (antinociception in the tail-flick, and hot-plate tests, and hypothermia) in male ICR mouse after acute oral nicotine administration. Administration of intra peritoneal (ip) methoxsalen significantly increased nicotine's Cmax, prolonged the plasma half-life (fourfold decrease) of nicotine, and increased its area under the curve (AUC) compared with ip vehicle treatment. Methoxsalen pretreatment prolonged the duration of nicotine-induced antinociception and hypothermia (15mg/kg, po) for periods up to 6- and 24-hr postnicotine administration, respectively. Additionally, methoxsalen potentiated nicotine-induced antinociception and hypothermia as evidenced by leftward shifts in nicotine's dose-response curve. Furthermore, this prolongation of nicotine's effects after methoxsalen was associated with a parallel prolongation of nicotine plasma levels in mice. These data strongly suggest that variation in the rates of nicotine metabolic inactivation substantially alter pharmacological effects of nicotine given orally. We have shown that the pharmacological effects of inhibiting nicotine's metabolism after oral administration in mice are profound. Our results suggest that inhibiting nicotine metabolism can be used to dramatically enhance nicotine's bioavailability and its resulting pharmacology, which further supports this inhibitory approach for clinical development of an oral nicotine replacement therapy.

High-Throughput Determination of Nicotine in Plasma by Ultrasonication Enhanced Hollow Fiber Liquid-Phase Microextraction Prior to Gas Chromatography

In high-throughput ultrasonication enhanced hollow-fiber liquid-phase microextraction (H-U-HF-LPME), ultrasonication was introduced into HF-LPME to enhance the mass transfer rate of the analytes in the two immiscible liquid phases, which resulted in a very short time for extraction equilibrium and a high-throughput analysis. Several parameters were investigated and optimized (such as extraction solvent, temperature of sample, frequency and intensity of ultrasonication, volume of extractant, extraction time, ionic strength of the sample and sample concentration). Based on the results of this study, nicotine was first extracted from a 1.5 mL sample solution under the optimum conditions (ultrasonic power of 50 W with a frequency of 60 kHz, extraction time of 10 min, sodium chloride concentration of 5 mol/L and temperature of 37°C). Next, 0.5 µL of acceptor solution inside the hollow fiber was automatically injected into a gas chromatograph with a flame ionization detector. The results of this study illustrated that the limit of detection, relative standard deviation (n = 6), relative recovery and enrichment factor of nicotine were 0.06 µg/L, 3%, 99.8% and 16.6, respectively. Finally, H-U-HF-LPME was successfully applied for the determination of nicotine in plasma.

Plasma Choline, Nicotine Exposure, and Risk of Low Bone Mineral Density and Hip Fracture: The Hordaland Health Study

Choline, obtained from diet and formed by biosynthesis, is the immediate precursor of betaine. Animal studies suggest an impact of choline on bone metabolism. We examined the associations of plasma choline and betaine with bone mineral density (BMD), the risk of hip fractures, and possible effect-modification by nicotine exposure. The Hordaland Health Study (1998 to 2000) included 7074 women and men (ages 46 to 49 or 71 to 74 years). In 5315, BMD was measured. The oldest (n = 3311) were followed for hip fractures through 2009. Risk associations were studied by logistic and Cox regression by comparing the lowest and middle tertiles with the highest, as well as trends across tertiles of plasma choline and betaine. In analyses adjusted for sex and age, participants in the lowest (odds ratio [OR] = 2.00, 95% confidence interval [CI] 1.69-2.37) and middle (OR = 1.39, CI 1.17-1.66) tertiles of plasma choline had an increased risk of low BMD (lowest quintile) (p trend < 0.001). Separate analyses for sex and age groups revealed the strongest relations in elderly women (lowest tertile: OR = 2.84, CI 1.95-4.14; middle tertile: OR = 1.80, CI 1.22-2.67, p trend < 0.001), and highest OR among those in the lowest tertile who were exposed to nicotine (OR = 4.56, CI 1.87-11.11). Low plasma choline was also associated with an increased risk of hip fracture in elderly women and men (lowest tertile: hazard ratio [HR] = 1.45, CI 1.08-1.94; middle tertile: HR = 1.13, CI 0.83-1.54, p trend = 0.012). In elderly women, the HR for hip fracture was 1.90 (CI 1.32-2.73) and 1.36 (CI 0.92-1.99) (p trend < 0.001) for lowest and middle tertiles of choline, and the highest HR was found among women in the lowest tertile exposed to nicotine (HR = 2.68, CI 1.16-6.19). Plasma betaine was not related to BMD or hip fracture. Low plasma choline was associated with low BMD in both sexes and increased the risk of hip fracture in elderly women. These results should motivate further studies on choline, nicotine exposure, and bone metabolism.