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Concern has been raised about the presence of toxicants in electronic cigarette (EC) aerosol, particularly carbonyl compounds (e.g., acrolein) that can be produced by heating glycerol and glycols used in e-liquids. We investigated exposure to carbon monoxide (CO), nicotine (by measuring cotinine in urine), and to acrolein (by measuring its primary metabolite, S-(3-hydroxypropyl)mercapturic acid (3-HPMA) in urine) before and after 4 weeks of EC (green smoke, a "cig-a-like" EC, labeled 2.4% nicotine by volume) use, in 40 smokers. Thirty-three participants were using EC at 4 weeks after quitting, 16 (48%) were abstinent (COvalidated) from smoking during the previous week (EC only users), and 17 (52%) were "dual users." A significant reduction in CO was observed in EC-only users [-12 ppm, 95% confidence interval (CI), -16 to -7, 80% decrease) and dual users (-12 ppm, 95%CI, -19 to -6, 52% decrease). Cotinine levels also declined, but to a lesser extent (EC-only users: -184 ng/mg creatinine; 95% CI, -733 to -365, 17% decrease; and dual users: -976 ng/mg creatinine; 95%CI, -1,682 to -270, 44% decrease). Mean 3-HPMA levels had decreased at 4 weeks by 1,280 ng/mg creatinine (95%CI, -1,699 to -861, 79% decrease) in EC-only users and by 1,474 ng/mg creatinine (95%CI, -2,101 to -847, 60% decrease) in dual users. In dual users, EC use significantly reduced exposure to CO and acrolein because of a reduction in smoke intake. EC may reduce harm even in smokers who continue to smoke, but long-term follow-up studies are needed to confirm this. Cancer Prev Res; 8(9); 873-8. Ó2015 AACR.

BackgroundDelivering 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.MethodsTwelve 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.ResultsEleven smokers provided usable data. None of the EC matched cigarettes in nicotine delivery (C max = 17.9 ng/ml, T max = 4 min and AUC0–>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, AUC0–>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, AUC0–>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, AUC0–>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 AUC0–>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.ConclusionsEC 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.

Aims To assess the pharmacokinetic (PK) profile of, and users' reactions to, Juul (59 mg nicotine/ml) as an indication of its therapeutic and dependence potential. Design Cross-over, within-subjects study in which participants attended after overnight abstinence on separate sessions and smoked a cigarette or used Juul or eight other types of e-cigarettes (EC) ad libitum for 5 minutes. The Juul product used was the version available in the United States that has more nicotine in the eliquid than the one available in the European Union. Setting Laboratory setting in the United Kingdom. Participants Twenty dual users (smokers who also vape) provided data on Juul and cigarettes, with eight also providing data on other EC products. Measurements At each session, number of puffs taken was counted during the 5-minute product use period and blood samples were taken at baseline and at 2, 4, 6, 8, 10 and 30 minutes after starting smoking/vaping and analysed for nicotine. Participants also monitored their urges to smoke and rated the products on a range of characteristics. Findings Juul's PK profile was close to the PK profile of cigarettes [maximum concentration (C max ) = 20.4 versus 19.2 ng/ml; time to maximum concentration (T max ) = 4 versus 6 minutes; area under the curve (AUC): 307.9 versus 312.6, respectively]. Compared with other EC products, Juul had shorter T max [4 minutes, (IQR = 2.5-4.0) versus 6.3 minutes, (IQR = 4.7 -8.1), P = 0.012] and higher C max (28.9 (SD = 15.6) versus 10.6 (SD = 5.5), P = 0.013) despite a lower number of puffs (12.5 (SD = 4.2) versus 17.0 (SD = 4.2), P = 0.084). Compared with other e-cigarette products, it also provided faster reduction of urges to smoke and obtained more favourable subjective ratings.Conclusion Juul's PK profile and user ratings suggest that it could be more effective than other EC products in helping smokers to quit smoking, but it may also have a higher potential to generate regular use in non-smokers.