title: Nicotine Delivery and Vaping Behavior Duringad LibitumE-cigarette Access.
abstract: OBJECTIVE
  To characterize vaping behavior and nicotine intake duringad libitume-cigarette access.
  
  
  METHODS
  Thirteen adult e-cigarette users had 90 minutes of videotapedad libitumaccess to their usual e-cigarette. Plasma nicotine was measured before and every 15 minutes after the first puff; subjective effects were measured before and after the session.
  
  
  RESULTS
  Average puff duration and interpuff interval were 3.5±1.4 seconds (±SD) and 118±141 seconds, respectively. 12% of puffs were unclustered puffs while 43%, 28%, and 17% were clustered in groups of 2-5, 6-10, and >10 puffs, respectively. On average, 4.0±3.3 mg of nicotine was inhaled; the maximum plasma nicotine concentration (Cmax) was 12.8±8.5 ng/mL. Among the 8 tank users, number of puffs was positively correlated with amount of nicotine inhaled, Cmax, and area under the plasma nicotine concentration-time curve (AUC0→90min) while interpuff interval was negatively correlated with Cmaxand AUC0→90.
  
  
  CONCLUSIONS
  Vaping patterns differ from cigarette smoking. Plasma nicotine levels were consistent with intermittent dosing of nicotine from e-cigarettes compared to the more bolus dosing from cigarettes. Differences in delivery patterns and peak levels of nicotine achieved could influence the addictiveness of e-cigarettes compared to conventional cigarettes.
authors.affiliation: Assistant Professor, Division of Clinical Pharmacology and Experimental Therapeutics, Department of Medicine, University of California, San Francisco, CA.
authors.forename: Gideon
authors.initials: G
authors.lastname: St Helen
authors.affiliation: Postdoctoral fellow, Center for Tobacco Control Research and Education, University of California, San Francisco, CA.
authors.forename: Kathryn C
authors.initials: KC
authors.lastname: Ross
authors.affiliation: Physician, Division of Clinical Pharmacology and Experimental Therapeutics, Department of Medicine, University of California, San Francisco, CA.
authors.forename: Delia A
authors.initials: DA
authors.lastname: Dempsey
authors.affiliation: Chemist, Division of Clinical Pharmacology and Experimental Therapeutics, Department of Medicine, University of California, San Francisco, CA.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Havel
authors.affiliation: Research Chemist, Division of Clinical Pharmacology and Experimental Therapeutics, Department of Medicine, University of California, San Francisco, CA.
authors.forename: Peyton
authors.initials: P
authors.lastname: Jacob
authors.affiliation: Professor, Division of Clinical Pharmacology and Experimental Therapeutics, Department of Medicine, University of California, San Francisco, CA.
authors.forename: Neal L
authors.initials: NL
authors.lastname: Benowitz
keywords: addictive potential; e-cigarettes; nicotine pharmacokinetics; vaping patterns; vaping topography