E-cigarettes an evidence update A report commissioned by Public Health England

E-cigarettes: an evidence updateSpeed of nicotine delivery seems important for smokers’ satisfaction. Cigarettes delivernicotine very fast via the lungs. It is likely that to out-compete cigarettes, EC will need toprovide nicotine via the lungs as well. Although some EC products may already providea degree of lung absorption, most nicotine is probably delivered via a much slower routethrough buccal mucosa and upper airways, in a way that is closer to the delivery fromnicotine replacement medications than to the delivery from cigarettes.This tallies with two other observations. Vapers feel they are less dependent on EC thanthey were on cigarettes [126]; and non-smokers experimenting with EC do not find themattractive and almost none progress to daily vaping [127]. This contrasts with the factthat about half of adolescents who experiment with cigarettes progress to daily smoking[128].In addition to mechanical characteristics of EC and user puffing behaviour discussed inprevious sections, the composition of the chemicals used to produce the vapour,typically vegetable glycerol and/or propylene glycol (PG), may also influence nicotinedelivery. E-liquid with a mix of vegetable glycerol/PG was associated with better nicotinedelivery than a vegetable glycerol-only e-liquid with the same concentration of nicotine[129]. The presumed effect is that PG vaporises at a faster rate than vegetable glycerolwhen heated in the EC and so is able to carry more nicotine to the user.If EC continue to improve in the speed of nicotine delivery, they are likely to appeal tomore smokers, making the switch from smoking to vaping easier. It may be important inthis context to note that if the smoking-associated risk is removed, nicotine use by itself,outside pregnancy, carries little health risk and in fact conveys some benefits.Table 8: Studies examining nicotine intake in vapersStudy Participants EC Device Methods ResultsVansickelet al 2012[119]Vapor King(cigalike),18mg/ml nicotineVansickel&Eissenberg2012 [121]Yan &D’Ruiz2014 [129]20smokersnaïve toEC8 vapersusing ECforaverageof 12months23smokersOwn EC1 used 9 mg/ml6 used 18 mg/ml1 used 24 mg/ml4 types of Blu(cigalike) EC(1.6% to 2.4%)Marlboro cigaretteOvernight abstinence,baseline blood sample,after 5 mins 10 puffs,30 sec inter-puffinterval, 5 mins afterlast puff blood sample.Repeated 5x, 30 minsin betweenOvernight abstinence,Baseline blood, after 5mins 10 EC puffs at 30sec intervals, 5 and 15mins after first puffblood sample, 60 minad-lib vapingRandomised 6 sessions7-days get used to EC,36 h abstinence. EC =50x5 sec puffs, 30 sec72At end of lastpuffing boutplasma nicotineincreased from2.2 ng/ml atbaseline to 7.4ng/ml.Increase inplasma nicotinefrom 2.0 ng/ml to10.3 ng/ml in 5mins. Cmax =16.3 ng/ml at endof ad lib periodDuring controlledpuffing Cmax(ng/ml): EC 10.3to 18.9; cig 15.8