Assess the Influence of Nicotine Flux and Nicotine Form on Subjective Effects Related to Dependency

Nicotine Flux, a Potentially Powerful Tool for Regulating Nicotine Delivery From Electronic Cigarettes: Significance of Nicotine Flux to the Rate of Nicotine Delivery and Subjective Effect

Electronic nicotine delivery systems (ENDS) heat and vaporize a nicotine-containing liquid to produce an aerosol that can deliver nicotine to the blood and the brain. ENDS use has increased rapidly in the last decade, especially among youth: over 20% of US high school students are current ENDS users, and there is evidence of nicotine dependence in this population. Federal legislation has been proposed that would restrict ENDS liquid nicotine concentration to make ENDS "significantly less addictive and appealing to youth." However, these and other efforts to curb addiction by limiting nicotine liquid concentration are unlikely to succeed because nicotine emissions from ENDS depend on multiple variables. To achieve the intended public health aims, regulations targeting addiction must focus on nicotine delivery, not nicotine concentration. While nicotine delivery cannot be regulated directly, the rate at which an ENDS emits nicotine, the "nicotine flux", can be regulated and, importantly, predicted based on a few device design and operating variables. However, to date there is no empirical evidence demonstrating the relationship between flux and delivery, nor between flux and the subjective effects that support nicotine dependence. Closing this gap is essential for providing an effective framework for regulating ENDS. At the American University of Beirut, the investigators will assess the relationship between nicotine flux, form, and subjective effects. Participants will use ENDS devices with varying nicotine fluxes and forms. Dependency measures, such as urge to smoke, craving, and abstinence, will be assessed. The outcome will indicate the degree to which nicotine flux/form influence subjective effects related to dependency, puffing intensity, and exposure to toxicants. In summary, this project will provide the empirical evidence needed for public health agencies to use nicotine flux as an encompassing and convenient construct to regulate nicotine delivery from ENDS.

Assess the influence of nicotine flux and nicotine form on subjective effects. At AUB, the investigators will assess subjective effects (e.g. product liking, nicotine craving) and puffing topography for 130 participants who will undergo 5 ENDS use sessions (combinations 1-5) consisting of 2 bouts (10 puffs + 60min ad libitum) with 2 fluxes (16 and 32μg/s) x 2 forms (protonated, freebase) and a 0 nicotine condition. In addition, the investigators will use a state-of-the-art device to sample in situ a fraction of the aerosol generated during each puff to verify actual nicotine flux and form, and measure exposure to pulmonary toxicants (carbonyls). The investigators hypothesize that increasing nicotine flux and protonated nicotine will result in greater reductions of nicotine craving, and lower puffing intensity and carbonyl exposure. In addition, 10 participants that completed the five use sessions will attend the lab for one additional visit with the aim of determining the influence of puff-by-puff variation of ENDS power and liquid composition on puffing behavior and sensory effects. During this visit participants will complete three directed puffing bouts (10 puffs). In each bout, participants will alternate puffs between two identical ENDS devices differing by a single design factor (combinations 6-8).

Inclusion Criteria:

• Must be healthy and above 18 years of age
• Must be willing to provide informed consent, attend the lab, and abstain from tobacco/nicotine as required (participants will be instructed to abstain from nicotine/tobacco and/or ENDS use for ≥12h)
• A dual ENDS and tobacco user who reports daily use of ENDS (≥ 3 mg/ml nicotine) or cigarettes (any frequency) AND someday use (≥ 3 days/week) of ENDS (≥ 3 mg/ml nicotine) or cigarettes (any frequency) for the past 3 months or longer

Exclusion Criteria:

• History of chronic disease or an uncontrolled psychiatric condition
• History of or active cardiovascular disease, low/high blood pressure, seizures, regular use of a prescription medication (except vitamins/birth control)
• Past month use of cocaine, opioids, benzodiazepines, or methamphetamines
• Individuals who report using marijuana >15/30 days
• Women will be excluded if they are breast-feeding or pregnant
• Participants intending to quit tobacco/nicotine use in the next 30 days and referred to cessation treatment