RT Journal Article SR Electronic T1 Experimental tobacco marketplace: substitutability of e-cigarette liquid for cigarettes as a function of nicotine strength JF Tobacco Control JO Tob Control FD BMJ Publishing Group Ltd SP 206 OP 211 DO 10.1136/tobaccocontrol-2017-054024 VO 28 IS 2 A1 Derek A Pope A1 Lindsey Poe A1 Jeffrey S Stein A1 Brent A Kaplan A1 Bryan W Heckman A1 Leonard H Epstein A1 Warren K Bickel YR 2019 UL http://tobaccocontrol.bmj.com/content/28/2/206.abstract AB Background The experimental tobacco marketplace (ETM) provides a method to estimate, prior to implementation, the effects of new products or policies on purchasing across various products in a complex tobacco marketplace. We used the ETM to examine the relationship between nicotine strength and substitutability of alternative products for cigarettes to contribute to the literature on regulation of e-liquid nicotine strength.Methods The present study contained four sampling and four ETM purchasing sessions. During sampling sessions, participants were provided 1 of 4 e-liquid strengths (randomised) to sample for 2 days followed by an ETM purchasing session. The nicotine strength sampled in the 2 days prior to an ETM session was the same strength available for purchase in the next ETM. Each participant sampled and could purchase 0 mg/mL, 6 mg/mL, 12 mg/mL and 24 mg/mL e-liquid, among other products, during the study.Results Cigarette demand was unaltered across e-liquid strength. E-liquid was the only product to substitute for cigarettes across more than one e-liquid strength. Substitutability increased as a function of e-liquid strength, with the 24 mg/mL displaying the greatest substitutability of all products.Conclusions The present study found that e-liquid substitutability increased with nicotine strength, at least up to 24 mg/mL e-liquid. However, the effects of e-liquid nicotine strength on cigarette purchasing were marginal and total nicotine purchased increased as e-liquid nicotine strength increased.