TABLE 3.
Electronic and combustible cigarette history and nicotine pharmacokinetics by types of e-cigarettes used
| Variable | Cig-a-like | Fixed-power | Variable-power | Χ2 | p-value |
|---|---|---|---|---|---|
| n (%) | 12 (33.3) | 15 (41.7) | 6 (16.7) | 3.81 | 0.148 |
| A. Screening (mean, SD) | |||||
| Screening saliva cotinine (ng/mL) | 204 (103) | 193 (105) | 172 (58) | 0.19 | 0.909 |
| Cigarettes per day | 13.5 (6.4) | 12.3 (4.5) | 15.6 (10.9) | 0.16 | 0.925 |
| FTCD | 4.0 (1.9) | 4.6 (1.6) | 5.2 (2.9) | 1.22 | 0.544 |
| Days of e-cigarette use in past 30 | 18.2 (8.6) | 24.7 (5.9) | 24.5 (6.1) | 5.20 | 0.074 |
| E-cigarette Times Per Day | 6.7 (8.2) | 7.0 (5.0) | 13.3 (9.6) | 4.57 | 0.102 |
| E-cigarette Use Index | 5.1 (8.4) | 6.0 (4.8) | 10.0 (6.1) | 5.77 | 0.056 |
| E-cigarette to combustible cigarette use ratio | 0.4 (0.6) | 0.5 (0.5) | 0.8 (0.5) | 5.74 | 0.057 |
| B. Standardized session (mean, SD) | |||||
| Baseline plasma nicotine, e-cigarette arm (ng/mL) | 2.4 (4.1) | 1.6 (1.9) | 2.6 (2.4) | 2.25 | 0.325 |
| Baseline plasma nicotine, cigarette arm (ng/mL) | 2.3 (2.0) | 1.6 (1.5) | 3.7 (2.1) | 5.27 | 0.072 |
| E-liquid nicotine concentration (ug/mg) | 20.2 (13.4) | 12.2 (7.4) | 9.4 (3.9) | 8.43 | 0.015 |
| E-liquid consumed (mg) | 56.3 (24.5) | 88.8 (57.3) | 165.8 (85.6) | 7.17 | 0.028 |
| Amount of nicotine inhaled (mg) | 1.2 (1.1) | 1.0 (0.7) | 1.6 (0.9) | 2.49 | 0.288 |
| Amount of nicotine retained (mg) | 1.1 (0.9) | 0.9 (0.7) | 1.5 (0.9) | 2.51 | 0.285 |
| Systemic nicotine retention (%) | 97.9 (4.9) | 93.9 (15.8) | 94.2 (13.7) | 0.10 | 0.952 |
| PK-estimated nicotine dose (mg) | 0.9 (0.7) | 0.7 (0.5) | 1.8 (1.0) | 6.01 | 0.050 |
| Cmax (ng/ml) | 5.6 (6.4) | 4.9 (4.2) | 10.0 (5.8) | 4.81 | 0.090 |
| Tmax (min) | 9.2 (6.1) | 5.6 (5.1) | 3.5 (1.6) | 3.96 | 0.138 |
| Half-life (min) | 125.1 (31.8) | 138.0 (43.0) | 161.5 (37.5) | 5.33 | 0.069 |
| AUC0→5 (ng/ml•min) | 20.4 (25.6) | 17.5 (15.5) | 37.6 (21.7) | 4.61 | 0.100 |
| AUC0→15 (ng/ml•min) | 67.2 (73.9) | 55.2 (43.4) | 123.4 (70.4) | 5.11 | 0.078 |
| AUC0→240 (ng/ml•min) | 520 (390) | 388 (271) | 1015 (591) | 5.89 | 0.053 |
| AUC0→∞ (ng/ml•min) | 718 (547) | 542 (379) | 1495 (802) | 6.01 | 0.050 |
| AUC0→5 per retained dose (ng/ml•min per mg) | 19.4 (10.5) | 31.2 (35.5) | 28.6 (17.8) | 2.36 | 0.307 |
| AUC0→15 per retained dose (ng/ml•min per mg) | 65.3 (29.0) | 111.2 (161.2) | 95.4 (64.6) | 0.23 | 0.890 |
| AUC0→240 per retained dose (ng/ml•min per mg) | 528 (206) | 808 (1175) | 797 (578) | 2.14 | 0.343 |
| AUC0→∞ per retained dose (ng/ml•min per mg) | 738 (383) | 1119 (1563) | 1173 (747) | 1.99 | 0.370 |
| Nicotine titration | 0.43 (0.36) | 0.39 (0.31) | 0.85 (1.03) | 2.03 | 0.363 |
Notes: The degree of freedom for all tests is 2. FTCD is Fagerström Test of Cigarette Dependence; E-cigarette times per day is the number of times e-cigarettes are used on days that they are used, assuming each “time” consisted of around 15 puffs or lasted around 10 minutes [ref [13]]; E-cigarette use index = [E-cigarette times per day × E-cigarette using days per month] ÷ 30 days; E-cigarette to cigarette use ratio = E-cigarette Use Index ÷ Cigarettes Per Day; Cmax is maximum plasma nicotine concentration; Tmax is time to maximum plasma nicotine concentration; AUC0→5 is area under the plasma nicotine concentration-time curve (AUC) from 0 to 5 minutes; AUC0→15 is AUC from 0 to 15 minutes; AUC0→240 is AUC from 0 to 240 minutes; AUC0→∞ is AUC from 0 to infinity; PK (pharmacokinetic)-estimated dose is the product of average population clearance of nicotine (~1200 mL/min) and AUC(0→∞) [ref [10]].