Changes in biomarkers of exposure and withdrawal symptom among Chinese adult smokers after completely or partially switching from combustible cigarettes to an electronic nicotine delivery system

This study assessed changes in biomarkers of exposure (BoE) after 5 days of completely or partially switching to an electronic nicotine delivery system (ENDS) use, compared with continued use of combustible cigarettes and smoking abstinence among Chinese adult smokers. A randomized, open-label, parallel-arm study was conducted among Chinese adult smokers who were naive ENDS users. Forty-six subjects were randomized to 4 study groups ( n = 11–12 per group): exclusive ENDS use, dual use of ENDS and cigarettes, exclusive cigarettes use, and smoking abstinence. Subjects were confined in clinic for 5 consecutive days and product use was ad libitum. Nicotine and its metabolites (cotinine and 3-hydroxycotinine), and BoEs (AAMA, CEMA, HEMA, HMPMA, 3-HPMA, SPMA, exhaled CO, and exhaled NO) were measured. Withdrawal symptom was measured using MNWS throughout the 5-day period. Six urine BoEs of volatile organic compounds decreased by 55.1–84.1% in the exclusive ENDS use group, which is similar to the smoking abstinence group (67.2–87.4%). The level of decrease was 56.8–70.4% in the dual use group and 10.7–39.0% in the cigarettes group. Urine total nicotine exposure had a non-significant increase in the exclusive ENDS use group, and plasma nicotine and cotinine showed a trend of increasing day by day. After completely or partially switching to ENDS use among Chinese smokers, exposure to selected toxicants were significantly decreased. The results of this study add to the body of evidence that exposure to toxic substance decreased among smokers after complete or partial switch from combustible cigarettes to ENDS use. As part of transition to experienced ENDS use, this study found that smokers of the initial stage who have no prior ENDS experience may increase nicotine intake after switching to ENDS use.