The effects of alcohol-containing e-cigarettes on young adult smokers

Highlights

• The consequences of using e-cigarettes that contain alcohol are unknown.

• In young adult smokers, the effects of matched commercial e-liquids containing either 23.5% or 0.4% alcohol were compared.

• Differences in acute subjective drug effects were not observed.

• Psychomotor performance improved under the trace, but not under the high alcohol condition.

• In some subjects, a urine alcohol metabolite became detectable after use of the high alcohol e-cigarette.

Abstract

Background

The liquids (e-liquids) used in an electronic cigarette (e-cigarette) contain myriad chemicals without adequate human inhalation safety data. Furthermore, the absence of e-liquid labeling requirements poses a formidable challenge to understanding how e-liquid constituents may promote nicotine addiction and/or have independent or synergistic biological effects when combined with nicotine. Ethyl alcohol is such a constituent, but has received little scientific interest in this context.

Methods

Using a randomized, double blind, crossover design, acute changes in subjective drug effects, motor performance and biochemical measures of alcohol and nicotine intake were evaluated after directed and ad lib puffing from two commercially available e-liquids containing nicotine (8 mg/ml), vanilla flavor and either 23.5% (high) or 0.4% (trace) alcohol.

Results

While no differences in subjective drug effects were observed between alcohol conditions, performance on the Purdue Pegboard Dexterity Test (PPDT) improved under the trace, but not under the 23.5% alcohol condition. Although plasma alcohol levels remained undetectable during testing, urine ethyl glucuronide (EtG), an alcohol metabolite, became measurable in three participants after puffing from the 23.5% alcohol e-cigarette.

Conclusions

Brief use of a widely available type of e-cigarette containing an e-liquid purchased from an internet vendor can negatively impact psychomotor performance and in some instances, produce detectable levels of a urine alcohol metabolite. Given the widespread and unregulated use of e-cigarettes, especially by youth and other vulnerable populations, further studies are needed to evaluate both the acute safety and long-term health risks of using alcohol-containing e-cigarettes.

Introduction

Identifying the human health consequences from inhaling the complex, poorly characterized, and evolving chemical mixtures associated with unregulated e-cigarette use is a daunting public health problem (Dutra and Glantz, 2014, Bhatnagar et al., 2014, Grana et al., 2014). While most e-liquids contain a ‘base mixture’ of glycerol and propylene glycol to which nicotine and various flavoring ingredients are added, ethanol (ethyl alcohol) is also a variable but frequent ingredient due to its ubiquity and utility as a solvent for e-liquid additives (Cai and Kendall, 2009, Ellicott, 2009, Herrington and Myers, 2015, Tygat, 2007, Valance and Ellicott, 2008). For example, in a recent chemical analysis or 42 commercial e-liquids, 30 contained ethyl alcohol (Varlet et al., 2015) and in a separate analysis of four leading brand first generation e-cigarettes, ethyl alcohol was found in all four although it was absent from their ingredient lists (Herrington et al., 2015). Importantly, alcohol was also found in the aerosols produced from these four e-cigarettes and an earlier analysis identified alcohol in an e-cigarette ‘mist’ (Laugesen, 2008).

Compared to the exhaustively studied effects of ingested alcohol, there are only a few studies on the behavioral effects of inhaled alcohol in humans, and these have focused on simulating low-level occupational exposures (Nadeau et al., 2003, Dumas-Campagna et al., 2014). To our knowledge, no previous studies have systematically examined the acute effects of alcohol inhaled from an e-cigarette. Likewise, the prevalence and patterns of alcohol exposure from e-cigarette use are largely unknown. While Internet-based anecdotal evidence indicates that some e-cigarette users ‘spike’ their e-liquids with various types of alcohol, the motivation for such use remains speculative (https://www.e-cigarette-forum.com/forum/threads/effects-of-adding-liquor-to-e-liquid.57173). In other instances, alcohol may be deliberately added to e-liquids to ‘thin’ viscous solutions as recommended by do-it-yourself (DIY) e-liquid forums (https://vaporizingtimes.com/alcohol-e-cig/) and ‘alcohol e-cigarettes’ may soon be entering the marketplace (U.S.P.T.O., 2015; http://www.clearette.com/blog/alcoholic-e-cigarettes/). Consequently, whether from commercially prepared products or from self-made e-liquids, many e-cigarette users are likely repeatedly inhaling variable levels of alcohol during routine e-cigarette use.

The possibility of widespread exposure to inhaled alcohol as a consequence of e-cigarette use has many significant public health implications, especially for youth and other vulnerable populations. While the amount of alcohol delivered by an e-cigarette may be insufficient to induce typical intoxication, any alcohol that is inhaled is likely to rapidly enter the brain and modulate its functions. For example, if inhaled alcohol has reinforcing properties, then its combination with nicotine may enhance nicotine reinforcement and promote progression to nicotine dependence in non-dependent users (Oliver et al., 2013). Because nicotine is a relatively weak primary reinforcer when compared to other drugs of abuse (e.g., cocaine, alcohol or opiates), the inhalation of combined nicotine and alcohol during e-cigarette use may promote the development and maintenance of nicotine addiction through exposure to this additional reinforcer (Sorge et al., 2009). Likewise, the co-administration of alcohol and nicotine may promote the progression to dependence for both substances given their synergistic effects on reinforcement (McKee et al., 2006, Tizabi et al., 2007). Finally, because inhalation is a reliable and rapid method for inducing alcohol dependence in rodents, chronic inhalation from alcohol-containing e-cigarettes may promote the development of alcohol dependence in humans (Gilpin et al., 2008), while episodic use may provide ‘priming’ doses that induce craving for alcohol (Duka et al., 1999, O’Malley et al., 2002).

To our knowledge, no previous studies have examined the acute subjective or motor effects of puffing from commercial e-liquids with a specified alcohol content. As a first step in addressing this knowledge gap, we assayed the alcohol concentration in a convenience sample of 31 e-liquids. The effects of the e-liquid with the highest concentration (23.5% alcohol) were then compared to an e-liquid with a trace amount of alcohol (0.4%) in a randomized, double blind, crossover study. Subjective drug effects, psychomotor performance, and changes from baseline in blood alcohol and urine ethyl glucuronide (EtG) levels were compared between the ‘nicotine + high alcohol’ and ‘nicotine + trace alcohol’ e-cigarette conditions.