Summary
Introduction:
This text is a summary of a scientific study investigating the stimulus effects of propylene glycol (PG) and vegetable glycerin (VG) in electronic cigarette liquids. The study aimed to assess the impact of these non-nicotine ingredients on the visibility of exhalant, taste, and smell, which have been associated with the abuse liability of conventional cigarettes. The study consisted of 16 electronic cigarette users, who completed five sessions, each with two sampling puffs from liquid formulations with varying PG and VG content.
Key Points:
* The study found that VG content was associated with greater reports of visibility of the exhalant (i.e., "cloud").
* Liquids with only PG or VG engendered lower reports of inhalation sensations (e.g., throat hit) and greater reductions of systolic blood pressure compared to mixtures of PG and VG.
* There was no effect of liquid formulation on the multiple-choice procedure, but puffs were rarely chosen over even the smallest monetary option ($0.05), suggesting minimal reinforcing efficacy.
* The study design included one practice day and four identical test days, with five liquid formulations (100/0, 75/25, 50/50, 25/75, 0/100 PG/VG) assessed in a random order.
* Participants completed one practice day to acclimate them to study procedures, followed by four identical test days, each approximately 3h long.
* The study used an EC with a refillable tank and adjustable power supply, and liquids were provided by a commercial vendor who verified formulation compositions.
* The study included control measures such as cardiovascular measures, puff topography, qSU-B, and VaS-SE.
* The outcome measures included the Duke Sensory questionnaire (DSq), Visual analog Scale - Post Sampling (VaS-PS), and Multiple Choice Procedure (MCP).
Main Message:
The main message of this study is that liquids containing greater concentrations of VG are more capable of producing visible exhalant, and mixtures of PG and VG engender greater airway sensory effects than either ingredient alone. These findings suggest that PG and VG could be important regulatory targets for reducing the abuse liability of electronic cigarettes. harm-reduction efforts could also better tailor ECs to increase smoking cessation efficacy by considering the stimulus effects of PG and VG.
Citation
harvanko a, Kryscio R, Martin C, Kelly T. Stimulus effects of propylene glycol and vegetable glycerin in electronic cigarette liquids. Drug and alcohol Dependence. 2019;194:326-329. doi:10.1016/j.drugalcdep.2018.08.039
