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Randomized Controlled Trial
. 2020 Apr 21;22(5):791-797.
doi: 10.1093/ntr/ntz130.

The Impact of E-liquid Propylene Glycol and Vegetable Glycerin Ratio on Ratings of Subjective Effects, Reinforcement Value, and Use in Current Smokers

Tracy T Smith  1   2 , Bryan W Heckman  1   2 , Amy E Wahlquist  2   3 , K Michael Cummings  1   2   3 , Matthew J Carpenter  1   2   3
Affiliations
Randomized Controlled Trial

The Impact of E-liquid Propylene Glycol and Vegetable Glycerin Ratio on Ratings of Subjective Effects, Reinforcement Value, and Use in Current Smokers

Tracy T Smith et al. Nicotine Tob Res. .

Abstract

Introduction: Electronic nicotine delivery systems (ENDS) vary on a wide range of characteristics that may affect reinforcement value and use. One characteristic is the ratio of two solvents commonly used in most e-liquids: propylene glycol (PG) and vegetable glycerin (VG). The goal of this study was to understand how PG/VG ratio affects subjective effects, reinforcement value, and tobacco use patterns among current smokers who try using ENDS.

Aims and methods: Current smokers with minimal ENDS use history (n = 30) sampled, in a double-blind fashion, three different e-liquids that varied in PG/VG ratio (70/30, 50/50, 0/100) while holding constant other aspects of the e-liquid and ENDS. Participants tried each e-liquid before rating the subjective effects on a modified version of the Cigarette Evaluation Questionnaire. Reinforcement value was assessed using a preference task where participants chose between the three e-liquids. The impact of each e-liquid on cigarette reinforcement was assessed using a modified version of the Cigarette Purchase Task. Participants were randomly assigned to receive one e-liquid to take home for 1 week.

Results: PG/VG ratio had minimal impact on most of the tested outcomes. Participants rated the highest PG concentration as having a stronger "throat hit" than the other two. There was no significant difference between the number of participants who preferred each of the PG/VG ratios in the preference assessment. PG/VG ratio did not affect cigarette or ENDS use during the sampling week.

Conclusions: These data suggest that PG/VG ratio has minimal impact on subjective effects and reinforcement value in ENDS naive current smokers.

Implications: These data suggest that PG/VG ratio, within the range that is commonly used, has minimal impact on subjective effects, reinforcement value, or uptake in current smokers with minimal ENDS experience.

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Figures

Figure 1.
Figure 1.
The impact of product and propylene glycol (PG)/vegetable glycerin (VG) ratio on subjective effects. Average product ratings on five subscales, throat hit, and vapor production after sampling each product. Significant pairwise difference from usual brand indicated by “*”. Significant difference from two other PG/VG ratios indicated by “+”.
Figure 2.
Figure 2.
Impact of propylene glycol (PG)/vegetable glycerin (VG) ratio on e-liquid preference. Number of participants preferring each of the available options during preference task when excluding (A) and including (B) the option to abstain. Ties are excluded (A = 4; B = 6).
Figure 3.
Figure 3.
The impact of e-liquid sampling and propylene glycol (PG)/vegetable glycerin (VG) ratio on cigarette smoking behavior. Average cigarettes smoked per day in each of the PG/VG ratio e-liquid groups during baseline naturalistic week (Days 1–8) and electronic nicotine delivery system (ENDS) sampling (Days 9–15). For participants who had more than 8 days included in baseline or 7 days included in the sampling week, additional days are not shown. Participants received the ENDS during their sampling visit on Day 9.
See this image and copyright information in PMC

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