Dose by design: How limits on nicotine flux and puff duration affect the abuse liability of electronic nicotine delivery systems

Introduction: Electronic nicotine delivery system (ENDS) product standards for nicotine flux (nicotine emitted/second), combined with limiting puff duration, could control nicotine dose and support ENDS regulations. We assessed behavioral and subjective abuse liability indices for ENDS varying in nicotine flux with fixed puff duration among people who smoke.

Methods: This within-subjects study included 32 adults who smoked cigarettes. Own-brand cigarettes (OB) and four unflavored ENDS were evaluated: no-flux (0μg/s), low-flux (36.01μg/s), cigarette-like-flux (90.03μg/s), and high-flux (180.06μg/s), with ENDS puff duration limited to 2s. Outcomes from behavioral economic choice tasks included demand intensity (drug purchase task [DPT]), cross-price elasticity (cross-product DPT), puffs earned (progressive ratio task [PRT]), and breakpoint (cross-product PRT). Subjective effects were nicotine abstinence symptoms (NAS), aversive effects, product liking, and sensation. Condition differences were analyzed using linear mixed models.

Results: All ENDS were associated with significantly lower demand intensity, puffs earned, NAS suppression, and liking compared to OB, yet would serve as OB substitutes. Low-flux ENDS were a significantly stronger OB substitute than cigarette-like-flux ENDS, and were associated with more puffs earned than no and high-flux ENDS. Compared with other ENDS, high-flux ENDS generally reduced NAS more, were less pleasant, tasted worse and produced more intense harshness/irritancy and throat hit.

Conclusions: ENDS abuse liability and substitution potential varies by nicotine dose, which could be controlled via product standards integrating nicotine flux and puff duration. ENDS that exceed a cigarette nicotine dose may not be necessary to encourage transition from cigarettes to ENDS.