A clinical laboratory model for evaluating the acute effects of electronic "cigarettes": nicotine delivery profile and cardiovascular and subjective effects

Abstract

Background: Electronic "cigarettes" are marketed to tobacco users as potential reduced exposure products (PREP), albeit with little information regarding electronic cigarette user toxicant exposure and effects. This information may be obtained by adapting clinical laboratory methods used to evaluate other PREPs for smokers.

Methods: Thirty-two smokers participated in four independent Latin-square ordered conditions that differed by product: own brand cigarette, "NPRO" electronic cigarettes (NPRO EC; 18 mg cartridge), "Hydro" electronic cigarettes (Hydro EC; 16 mg cartridge), or sham (unlit cigarette). Participants took 10 puffs at two separate times during each session. Plasma nicotine and carbon monoxide (CO) concentration, heart rate, and subjective effects were assessed.

Results: Own brand significantly increased plasma nicotine and CO concentration and heart rate within the first five minutes of administration whereas NPRO EC, Hydro EC, and sham smoking did not. Own brand, NPRO EC, and Hydro EC (but not sham) significantly decreased tobacco abstinence symptom ratings and increased product acceptability ratings. The magnitude of symptom suppression and increased acceptability was greater for own brand than for NPRO EC and Hydro EC.

Conclusions: Under these acute testing conditions, neither of the electronic cigarettes exposed users to measurable levels of nicotine or CO, although both suppressed nicotine/tobacco abstinence symptom ratings.

Impact: This study illustrates how clinical laboratory methods can be used to understand the acute effects of these and other PREPs for tobacco users. The results and methods reported here will likely be relevant to the evaluation and empirically based regulation of electronic cigarettes and similar products.

Figure 1

Mean data for nicotine blood plasma (panel A) and heart rate (panel B) as a function of condition and time. X-axes: time in minutes relative to product administration. Arrows represent the first and second product administrations. Y-axes: Top: nicotine blood plasma concentration (ng/ml), Bottom: heart rate (beats per minute). Filled symbols indicate a significant difference from baseline. An “a”, “b”, or “c” indicates that own brand was significantly different from sham, “Hydro” EC, or “NPRO” EC at that time point. A “d” indicates that “Hydro” EC was significantly different from sham at that time point. An “e” indicates that “NPRO” EC was significantly different from sham at that time point (Tukey’s HSD, p < 0.05). Unidirectional error bars represent one S.E.M.

Figure 2

Mean data for QSU Factor 1 ratings (panel A), ratings of “craving a cigarette” (panel B), ratings of “calm” (panel C), and ratings of “satisfying” (panel D) as a function of condition and time. X-axes: time in minutes relative to product administration. Arrows represent the first and second product administrations. Y-axes: subjective ratings. Filled symbols indicate a significant difference from baseline. An “a”, “b”, or “c” indicates that own brand was significantly different from sham, “Hydro” EC, or “NPRO” EC at that time point. A “d” indicates that “Hydro” EC was significantly different from sham at that time point. An “e” indicates that “NPRO” EC was significantly different from sham at that time point (Tukey’s HSD, p < 0.05). Unidirectional error bars represent one S.E.M.

Figure 3

Mean data for carbon monoxide (CO) as a function of condition and time. X-axis: time in minutes relative to product administration. Arrows represent the first and second product administrations. Y-axis: CO in parts per million (ppm). Filled symbols indicate a significant difference from baseline. An “a”, “b”, or “c” indicates that own brand was significantly different from sham, “Hydro” EC, or “NPRO” EC at that time point. A “d” indicates that “Hydro” EC was significantly different from sham at that time point. An “e” indicates that “NPRO” EC was significantly different from sham at that time point (Tukey’s HSD, p < 0.05). Unidirectional error bars represent one S.E.M.