Electronic cigarette effectiveness and abuse liability: predicting and regulating nicotine flux

Abstract

Electronic cigarettes (ECIGs) comprise an aerosolized nicotine delivery product category that provides consumers with probably unprecedented control over extensive features and operating conditions, allowing a wide range of nicotine yields to be obtained. Depending on the combination of such ECIG variables as electrical power input, geometry, liquid composition, and puff behavior, ECIG users can extract in a few puffs far more or far less nicotine than with a conventional combustible cigarette. These features of ECIG design and use present challenges for public health policy, central among which is the question of how to regulate nicotine delivery. In this commentary, we propose a conceptual framework intended to provide a convenient approach for evaluating and regulating the nicotine emitted from ECIGs. This framework employs nicotine flux to account for the total dose and rate at which nicotine reaches the user, 2 key factors in drug abuse liability. The nicotine flux is the nicotine emitted per puff second (e.g., mg/s) by a given ECIG design under given use conditions, and it can be predicted accurately using physical principles. We speculate that if the flux is too low, users likely will abandon the device and maintain conventional tobacco product use. Also, we speculate that if the flux is too high, individuals may suffer toxic side effects and/or the device may have higher-than-necessary abuse liability. By considering ECIG design, operation conditions, liquid composition, and puff behavior variables in combination, we illustrate how ECIG specifications can be realistically mandated to result in a target flux range.

Figure 1.

Some electronic cigarette product designs, heating element features, liquid components, and user behaviors likely related to nicotine and other toxicant delivery. Each box lists a subset of many variables, and the product of the number of choices in each box conceptually represents the number of configurations available.

Figure 2.

Nicotine flux versus product design and topography parameters for three hypothetical products. Nicotine flux is indicated by color. A hypothetical regulatory target range for product effectiveness is given as 25–45 μg/s. The areas enclosed by each product box represent the ranges of possible nicotine fluxes given the possible product characteristics (e.g., design, element, and liquid) and puff topography (e.g., puff duration and interpuff interval).