Differences in plasma nicotine pharmacokinetic profiles for various e-vapor products used by adult smokers under ad libitum vs. controlled use conditions
Plasma nicotine pharmacokinetic (PK) profiles are often used to characterize nicotine exposure from e-vapor products (EVP). The purpose of this analysis was to determine whether PK profiles are different when adult smokers (AS) use EVPs under ad libitum or controlled use conditions. We conducted a 6-way randomized crossover study in twenty-four AS smoking ≥10 cigarettes/day and had not used EVPs in the past month. AS used six different types of EVPs (tank- or cartridge-based) with different flavors and levels of nicotine under two use conditions (10 hours apart) – controlled use of 10 inhalations of 4-second duration with 60-second intervals (over ~10 minutes) and ad libitum use for 10 minutes. Nicotine plasma levels were measured periodically for 120 minutes. The maximum concentration (Cmax0-2hrs) and area under the curve (AUC0-2hrs) were higher under ad libitum vs. controlled use. On average, AS took ~twice as many puffs under ad libitum compared to controlled use and average puff duration ranged from 3.0 to 3.6 s for the six EVPs. The inter-individual variability (CV %) for Cmax0-2hrs was larger under ad libitum (53 %) than under controlled use (28 %). The identical use conditions under controlled use may provide a better method to compare nicotine PK from different types of EVPs. The high inter-individual variability under ad libitum use conditions may reflect behavioral aspects e.g. flavor preference and satisfaction. The pros and cons of each test condition for assessing nicotine PK will be discussed. These variability estimates may be used to design future studies with EVPs.