Nicotine delivery and user reactions to Juul EU (20 mg/ml) compared with Juul US (59 mg/ml), cigarettes and other e-cigarette products.

Rationale: The degree to which the EU version of Juul with 20 mg/ml nicotine (Juul EU) delivers nicotine to users is likely to determine its treatment potential.
Objectives: To compare the pharmacokinetic profile and user ratings of Juul EU, Juul US (59 mg/ml nicotine), cigarettes and other e-cigarette (EC) products.
Methods: In a within-subjects crossover design, 18 vapers used, at separate sessions, their own brand cigarette (OBC), Juul US and Juul EU for 5 min ad libitum, after overnight abstinence. Seven of the participants also tested eight other EC previously. Blood samples were taken at baseline and 2, 4, 6, 8, 10 and 30 min after initiating product use. Products were rated on a range of characteristics.
Results: Juul EU delivered less nicotine than OBC (t(13) = -4.64 p < .001) and than Juul US (t(13) = -6.40, p < .001): AUC _0 ≥ 30 77.3, 324.8 and 355.9, respectively. Maximum nicotine concentration (C _max ) was also much lower for Juul EU than Juul US (z = -3.59, p < .001): C _max 3.8 ng/ml vs 21.1 ng/ml, respectively. Juul EU was perceived to relieve urges to smoke less than Juul US (z = -2.29, p = .022) and to provide less nicotine (z = -2.57. p = 0.010). Juul EU delivered less nicotine than refillable EC (C _max : t(6) = 3.02, p = 0.023; AUC _0 ≥ 30 : z = -2.20, p = 0.028) and also less than cig-a-like EC, though the difference did not reach significance (C _max : t(6) = 2.49, p = 0.047; AUC _0 ≥ 30 : z = -1.99, p = 0.046). Subjective ratings of Juul EU and other EC products were similar.
Conclusions: Juul EU delivers much less nicotine to users than Juul US, and also less than refillable EC products. It may thus have more limited potential to help smokers quit.