Reductions in biomarkers of exposure, impacts on smoking urge and assessment of product use and tolerability in adult smokers following partial or complete substitution of cigarettes with electronic cigarettes.

Background: Electronic cigarettes (e-cigarettes) are popular alternatives to conventional cigarettes among adult smokers wishing to reduce their exposure to harmful smoke constituents. However, little information exists on the relative internal exposures resulting from the exclusive or dual use of e-cigarettes.

Methods: Measurements of product use; adverse events; changes in smoking urge; and blood, urine and exhaled breath biomarkers of exposure (BoE) representing toxicants believed to contribute to smoking related diseases were made at baseline and after five days of product use in 105 clinically-confined smokers randomized into groups that partially or completely substituted their usual brand combustible cigarette with commercial e-cigarettes, or discontinued all nicotine and tobacco products.

Results: Subjects switching to e-cigarettes had significantly lower levels (29 %-95 %) of urinary BoEs after 5 days. Nicotine equivalents declined by 25 %-40 %. Dual users who substituted half of their self-reported daily cigarette consumption with e-cigarettes experienced 7 %-38 % reductions, but had increases (1 %-20 %) in nicotine equivalents. Blood nicotine biomarker levels were lower in the cessation (75 %-96 %) and e-cigarette use groups (11 %-83 %); dual users had no significant reductions. All groups experienced significant decreases in exhaled CO (27 %-89 %). Exhaled NO increases (46 %-63 %) were observed in the cessation and e-cigarette use groups; dual users had minimal changes. By Day 5, all groups had greater reductions in smoking urge compared to cessation. However, reductions were larger in the dual use group. No serious adverse events were observed.

Conclusions: Exposures to harmful smoke toxicants were observed to be lower in smokers who completely or partially replaced their cigarettes with e-cigarettes over five days.