Vaping: parallels with cigarette smoking and management approaches in Singapore

INTRODUCTION

Vaping is the act of inhaling aerosolised substances, also known as e-liquids, delivered via devices called electronic nicotine delivery systems or ENDS, which may or may not contain nicotine. Electronic cigarettes (e-cigarettes) were created in Hong Kong in 2003 by Hon Lik, a pharmacist, to deliver nicotine vapour without smoke.[1] Though the delivery devices have morphed over time, the basic mechanism still requires the electronic heating of a liquid through a metal coil to cause the formation of vapour delivered through a vessel.

The exponential growth in popularity of e-cigarettes is alarming, with increasing use among youths and never-smokers. It has been marketed as a ‘safer’ alternative to smoking. The addition of flavours and innovative industry marketing strategies have led to a wider acceptance of this myth, further increasing its popularity.[2] Since its conception, the use of electronic devices to deliver nicotine has caught on rapidly, and the word “vape” became Oxford’s word of the year in 2014.[3] Singapore was quick to act, making vaping illegal before the fad could quickly reach its shores and slapping hefty fines with jail time for possession, purchase, use, selling or distribution of items related to e-cigarettes. Despite Singapore’s strong stance against vaping, there was still a 58% increase in possession, use and purchase of e-cigarettes reported in 2023.[4]

Electronic vs. combustible cigarettes

Vaping requires the evaporation of liquid substances through a heating coil that rapidly cools, forming the vapour. This differs from combustible tobacco, where there is direct burning of the layers that make up a cigarette.[5] Electronic cigarettes, similar to combustible tobacco, work as a conduit to deliver nicotine. While other substances, such as chemicals, tar and heavy metals, are inhaled together in cigarettes, vape liquids can contain a variety of substances like tetrahydrocannabinol, and cannabidiol, together with a mixture of solvents such as vegetable glycerin and propylene glycol.[5] There has also been increasing concern about teens in Singapore using Kpods, e-cigarettes containing etomidate, an anaesthetic agent.[6] Although vaping has been advertised to be ‘less harmful’ than smoking cigarettes, it still contains thousands of potentially damaging compounds that are inhaled and absorbed rapidly through the respiratory system, effectively distributing its toxic compounds throughout the body.[2,7]

Present and potential dangers

The threat of harm from cigarette smoking has been discussed and proven ad nauseam, with clear evidence linking it to increased risks of malignancy, cardiovascular disease, infections, and impaired wound healing. Tobacco is one of the biggest causes of preventable deaths, regardless of gender or race.[8,9,10,11] Unlike vaping, tobacco smoking has been practised for centuries, with evidence of its harm only emerging in recent decades. For vaping, the evidence is still in its infancy, yet the signal of potential irreparable harm is strong and continues to grow with ongoing research.

The unifying link between the two devices is their ability to effectively deliver nicotine, a highly addictive compound. Nicotine is absorbed rapidly through the buccal mucosa and lungs to reach the pulmonary venous circulation and subsequently crosses the blood-brain barrier. It then binds to nicotinic acetylcholine receptors (nAChRs), releasing multiple neurotransmitters such as dopamine that signal a pleasurable experience.[12,13] E-liquids can contain high nicotine content, while illicit vape pods have variable concentrations of nicotine.[7] The use of a cigarette ends when the stick burns down. Users of electronic cigarettes, however, can potentially inhale continuously as long as the battery on the device prevails, a phenomenon known as ‘grazing’.[14] Exposure to high levels of nicotine can be toxic to users, causing tremors, tachycardia and elevated blood pressure.[7] Central and peripheral nervous system shutdown and cardiac arrest have also been reported, especially when e-liquids were ingested.[15]

Similar to cigarette smoking, vaping has been associated with worsening control of underlying lung disease, with increased asthma exacerbation rates with more serious symptoms.[5] Increase in oxidative stress and aldehyde-detoxification can potentially lead to small airway destruction, with mouse models showing signs of chronic obstructive pulmonary disease (COPD) pathology. Interestingly, the substances that contribute to the flavours within the vape devices, such as ‘cinnamon ceylon’, have different cytotoxic potential, while some substances like menthol enhance the cytotoxicity of e-cigarettes.[16]

Studies have shown that people who vape have higher blood pressure, elevated heart rate, increased arterial stiffness and greater platelet activation.[17] These reported changes are similar to those from smoking conventional tobacco. There is a need for longer-term follow-up studies to determine their long-term effects, although indications of increased cardiovascular risks are present. Impact on the neurological system has also been described, with tremors and seizures reported in the literature.[5] Short-term memory deficits and hyperactivity experienced by people who vape may be related to nicotine. Additionally, long-term neuroinflammatory properties are increasingly reported.[7]

Acute lung injuries

Similar to cigarettes, acute exposure to e-cigarettes can increase airway inflammation.[7] Increased expression of inflammatory cytokines and decreased mucociliary clearance have been demonstrated with acute exposure to e-cigarettes.[7] Lung endothelial barrier dysfunction has been demonstrated in studies where mice received nebulised e-liquids.[18] In vivo studies have shown an increase in risk of respiratory infections with inhalation of e-liquids.[19]

The most concerning presentation is respiratory failure, described as electronic cigarette, or vaping, product use-associated lung injury (EVALI). Attributed to the presence of tetrahydrocannabinol-containing products, sometimes mixed with vitamin E acetate oils, patients present with fever and severe respiratory failure, often requiring mechanical ventilation.[20] Patients also present with acute onset of cough, dyspnoea and pleuritic chest pains, along with bilateral diffuse infiltrates in the lungs. Treatment is mainly supportive with no clear pharmacological antidotes.[21]

Long-term possibilities

Cigarette smoking is a major risk factor for lung cancer. Although clear links between lung cancer and vaping have not been established, the potential is certainly there. E-liquids have been shown to contain aldehydes, formaldehyde, acrolein, metals such as cadmium, flavouring chemicals such as pulegone, and other potential oncogenic compounds. Some of these are delivered at a higher concentration and more effectively through a vape device.[1,5,7] Oncogenicity is not confined to the lungs. Aromatic amines and polyaromatic hydrocarbons found in e-liquids are known to cause bladder cancer in humans. The heavy metals linked to head and neck cancers and the potential for lung metastasis in breast cancer sufferers have been reported.[1]

Management

A systematic approach is required to identify people who vape, provide brief advice on quitting, and facilitate referral for vaping cessation support. The Ask (A), Brief advice (B) and Cessation support (C) framework has been suggested, mimicking previous successful identification of cigarette smokers.[22] Exposure history — which may eventually be important — can be categorised into ‘ever-exposed’ for ever-users of e-cigarettes, and daily users with puff frequency measured as minimal (<2 puffs per hour), moderate (3–4 puffs per hour) and heavy (≥5 puffs per hour).[23] This provides an estimation of an individual’s level of usage.

Behavioural management

Behavioural treatments such as counselling and nicotine replacement therapy have been used for vaping cessation.[24] This approach is logical and mirrors that used for smoking cessation, as the active ingredient, nicotine, is what fuels the addiction for both. However, the counselling approaches for the two should differ. Since vaping generally involves adolescents and young adults, the mode of counselling should, therefore, be tailored to the specific population being treated.

The motivations for vaping differ across gender, age groups and social influences. In particular, female youths tend to be more affected by social influences as compared to young adults, highlighting the utility of social-centric behavioural approaches for this group.[25] On the other hand, when compared to youths, young adults are more influenced by substance use as a trigger for relapse, and hence, counselling approaches for this group should address polysubstance use.[25] One of the cited differences was that, compared to youths, young adults are generally of legal age to purchase tobacco and vape products in most countries, allowing easy access to these and other substances.[25] The greatest challenge lies in changing the prevailing mindset that vaping is harmless or safer than cigarette smoking. This perception is reinforced by social media, which exerts a strong influence, with its persuasive advertising and spread of misinformation. Addressing these issues will require collective effort and strong political will, continuing the war against not only the tobacco industry but also the emerging vaping industry.

There is evidence that a tailored text message intervention is effective in vaping cessation among young adults, with a Cochrane review reporting that text message-based interventions may help young people quit vaping.[26,27] Further research needs to be done to show the effectiveness of different types of behavioural interventions.

Pharmacotherapy

While there is limited guidance on effective ways to quit nicotine-containing e-cigarettes,[27] it may be reasonable to extrapolate from the successful use of pharmacological agents in cigarette smoking cessation to vapping cessation. Nicotine replacement therapy (NRT) has been shown to be effective for achieving long-term smoking abstinence by reducing cravings and withdrawal symptoms through nicotine replacement.[28] As e-cigarettes also deliver nicotine efficiently and the primary challenge for individuals seeking to quit vaping likely stems from nicotine addiction, NRT may have a similar role in supporting vaping cessation.

The amount of nicotine in each vape pod can range widely, even up to 60 mg/mL. The voltage and coil resistance of e-cigarettes can also vary such that the modified pods deliver higher doses of nicotine.[13] Nevertheless, the amount of nicotine contained within the vape pod may be estimated and dosed accordingly. Using the nicotine patch as an example, NRT may be dosed at a 7 mg or 10 mg patch, with additional breakthrough NRT such as lozenges, mouth sprays and gums, for people inhaling 10 mg or less of nicotine per day. Similarly, if the person is vaping more than 15 mg of nicotine per day, a 21 mg or 25 mg nicotine patch may be used, along with breakthrough replacements. Box 1 presents the suggested replacement dosing from Singapore’s Clinical Guidance for Care of People Who Vape.[22]

Box 1.

Suggested dosing of nicotine replacement therapy (NRT) for vaping cessation.^a

1. Assess the best estimate of the nicotine amount taken per day based on the known content of vape devices.

2. Prescribe NRT for 4 weeks or until the next appointment if within 4 weeks.

NRT Dosing:

• ≤7 mg nicotine/day: Nicotine 7 mg/24 h patch daily

• 8–14 mg nicotine/day: Nicotine 14 mg/24 h patch daily

• ≥15 mg nicotine/day: Nicotine 21 mg/24 h patch daily

PLUS

Nicotine 1 mg lozenge OR 2 mg gum OR 1 mg mouth spray for breakthrough cravings (to stop once symptoms such as nausea/vomiting/headache/dizziness occur)

^aSource: Clinical Guidance for Care of People Who Vape[22]

Additionally, NRT may be offered to women who are pregnant and/or breastfeeding, adolescents/youths and people with comorbid mental illness.[22] Bupropion and varenicline are both non-nicotine oral therapies that are approved for smoking cessation. While their use in vaping cessation is still limited, there is low-certainty evidence that varenicline may also help people quit vaping.[27] Cytisine, a plant derivative, is a partial agonist at the alpha-4 beta-2 nicotinic acetylcholine receptor responsible for the central effects of nicotine. Although it has been utilised as a smoking cessation pharmacotherapy in Eastern Europe, Canada and the United Kingdom, a Cochrane systematic review has found limited evidence for its efficacy due to methodological imprecision and potential bias.[27]

CONCLUSION

The vaping scourge has escalated exponentially, driven by misleading advertisements and inaccurate safety claims propagated by the tobacco and vaping industry. We should not wait until more lives are lost to prove the harmful effects of e-cigarettes, while those who are ready to quit should not be denied treatment. The medical fraternity has a strong calling to stem the rise in vaping and to render assistance to people who are addicted to nicotine delivery products.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.