E-cigarettes: Safe to recommend to patients?
ABSTRACTElectronic cigarettes (e-cigarettes)—devices that generate a nicotine vapor that can be inhaled by the user in a fashion that mimics the experience of smoking—are increasing in popularity, and many people seem to view them as reasonable alternatives to nicotine replacement therapy to help them refrain from smoking. Physicians should not encourage such a view. E-cigarettes are unregulated nicotine delivery systems that have never been subjected to any kind of testing of safety or of efficacy as nicotine replacement therapy. Moreover, for young people who have never smoked, these devices could potentially serve as a gateway drug.
KEY POINTS
- Although the vapor from e-cigarettes does not contain any tobacco combustion products, which are believed to be responsible for most of the adverse health effects of smoking, it does contain nicotine, which is addictive and poses health risks by itself.
- E-cigarette vapor also contains propylene glycol, which has not been adequately studied with regard to its safety when inhaled deeply and repeatedly. Also present are a variety of additives and contaminants.
- E-cigarette manufacturers make no therapeutic claims about their products, and therefore the US Food and Drug Administration does not regulate them as it does nicotine replacement therapy.
Contaminants
The issue of adulterants is common to both e-cigarettes and nicotine replacement therapy. Several unlisted substances have been found in analyzed samples of e-cigarette fluid, including tobacco-specific nitrosamines (TSNAs), diethylene glycol (found in only one e-cigarette cartridge), cotinine, anabasine, myosmine, and beta-nicotyrine.22 The tobacco-specific nitrosamines N´-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), N-nitrosoanabasine, and nitrosoanatabine have been found in five e-cigarette cartridge samples from two manufacturers in amounts similar to those found in nicotine replacement products.22
Goniewicz et al38 tested the vapor generated by 12 e-cigarette brands and found trace amounts of TSNAs. NNN was present in the vapor of eight of the samples in concentrations ranging from 0.8 to 4.3 ng per 150 puffs, and NNK in the vapor of nine of the samples in concentrations ranging from 1.1 to 28.3 ng per 150 puffs. Neither NNN nor NNK was found in blank samples nor with the Nicorette inhalator tested in the same study.38
Because TNSAs can be formed from nicotine and its metabolites, there is also concern that cancer-causing nitrosamines may be formed from nicotine after it is absorbed into the body (ie, endogenously). While endogenous formation of NNK from nicotine has never been demonstrated, endogenous formation of NNN has been seen in some nicotine patch users.39 The presence of these nitrosamines has raised concern that e-cigarettes and nicotine replacement therapy may have carcinogenic potential. The amounts of tobacco-specific nitrosamines found in e-cigarettes are also found in some nicotine replacement products.40
Investigators have examined a possible connection between e-cigarettes and potentially carcinogenic carbonyl compounds, including formaldehyde, acetaldehyde, and acrolein. Formaldehyde (a known carcinogen) and acetaldehyde (a potential carcinogen) have been detected in e-cigarette cartridges and vapor.38,41–43 Acrolein, a mucosal irritant, has been found in e-cigarette vapor.38,43 Goniewicz et al38 suggested that acrolein may be formed by the heating of the glycerin contained in the e-cigarette solution.
An extensive review of the studies of possible contaminant exposures (including polycylic aromatic hydrocarbons, TSNAs, volatile organic compounds, diethylene glycol, and inorganic compounds) with e-cigarette use according to occupational hygiene standards concluded that there was no cause for concern about increased health risk.37 The study by Goniewicz et al also concluded that using e-cigarettes instead of traditional cigarettes may significantly reduce exposure to some tobacco-specific toxins.38
E-CIGARETTES VS NICOTINE REPLACEMENT
Traditional nicotine replacement therapy products are regulated by the FDA and therefore standardized in terms of their contents. E-cigarettes, on the other hand, are unregulated vehicles for supplying nicotine, and may pose other health risks. One such risk is related to exposure to propylene glycol, which has never been studied under conditions (in terms of mode of delivery, frequency of dosing, and total duration of exposure) that approximate the exposure associated with e-cigarettes. Furthermore, the high concentration of nicotine in e-cigarette fluid poses a real risk of toxicity and potentially fatal overdose.
Nicotine replacement therapy and e-cigarettes both maintain addiction to nicotine if used in a harm-reduction strategy as a maintenance medication. Whether the ongoing nicotine addiction makes it more likely that individuals would switch back and forth between nicotine replacement and tobacco-based products is not clear. Also not known is whether e-cigarettes may serve as the “gateway drug” by which teens enter into nicotine addiction, but we believe that the potential exists, as these products are potentially more appealing in terms of the lack of pungent smell, the perception of safety, and the variety of flavors of e-cigarettes.
The efficacy of nicotine replacement therapy in improving smoking cessation has been reviewed extensively elsewhere37 and is beyond the scope of this article. E-cigarettes may be appealing to many cigarette smokers because they deliver smokeless nicotine, and they more closely emulate the actual experience of smoking compared with traditional nicotine replacement therapy. Though some evidence suggests that e-cigarettes may be modestly effective in helping tobacco smokers quit nicotine, they are not FDA-approved for smoking cessation and are not marketed for that indication.44 Medical practitioners should see them for what they are: a new nicotine product with a novel delivery system that is not approved as treatment. Because of the inherent risks involved with e-cigarettes, medical practitioners are best advised to remain neutral on the relative value of e-cigarettes and should continue to motivate patients to discontinue nicotine use altogether.
