Bullen and colleagues investigated the relationship between tobacco product type, nicotine delivery rate and peak nicotine concentration.17 In a cross-over study, eight nicotine-dependent participants used an e-cigarette (Ruyan V8, 16 mg nicotine), a nicotine inhaler (Nicorette, 10 mg nicotine; n=9), and smoked an own brand cigarette (n=9). Significant increases in nicotine concentration occurred only with own brand cigarettes. On average, peak venous plasma nicotine levels were achieved at 19.6 min following the initial e-cigarette puff, slower than with the own brand cigarette but more rapid than with the nicotine inhaler. This nicotine kinetic profile is also more rapid than smokeless tobacco products.18 Given the slower nicotine absorption profile, the authors suggest that e-cigarette aerosol may deliver nicotine through the buccal membranes (as with nicotine inhalers and smokeless tobacco) and the respiratory tract (similar to traditional cigarettes).
Eissenberg described preliminary findings from a cross-over study in which 16 smokers smoked their own brand cigarette, two brands of 16 mg nicotine e-cigarettes (NJOY and Crown 7), and puffed on an unlit own brand cigarette in a control condition.19 E-cigarette flavour (menthol or regular) was matched to the participant's preferred cigarette flavour category. In a controlled puff setting, both e-cigarette brands failed to increase plasma nicotine concentrations, whereas own brand cigarettes increased nicotine levels.