History repeats itself: Role of characterizing flavors on nicotine use and abuse

Restrictions of cigarette and e-cigarette flavor and filter ventilation on demand and substitution in the Experimental Tobacco Marketplace

SIGNIFICANCE

Tobacco product design features, including flavors and cigarette filter ventilation, are subject to regulation. This study examined the effects of cigarette and e-cigarette flavors on demand and substitution by preferred cigarette flavor and ventilation in the Experimental Tobacco Marketplace (ETM).

METHODS

In a mixed between-group (usual cigarette flavor and ventilation)/within-subject design (policy conditions), individuals who use tobacco (n=176 cigarette (60.5 % female); n=91 multiple products (26.7 % female)) were recruited using Ipsos and InnovateMR, completed purchasing trials with increasing cigarette prices in the ETM. Participants were exposed to four conditions in a 2×2 factorial design with cigarette flavors restricted or unrestricted and e-cigarette flavors restricted or unrestricted.

RESULTS

In individuals who exclusively smoke cigarettes: 1) Cigarette menthol restrictions decreased willingness to purchase cigarettes (OR: 0.001; 95 % CI: 0.00002, 0.015) for individuals that prefer menthol cigarettes and increased willingness to purchase NRT (OR: 4.02; 95 % CI: 1.47, 11.0), 2) cigarette menthol restrictions reduced demand for cigarettes in individuals who smoke menthol cigarettes (p<0.001), 3) e-cigarette flavor restrictions reduced the degree of e-cigarette substitution in individuals who smoke menthol cigarettes (p=0.028), and 4) preference for higher cigarette filter ventilation was associated with higher demand for cigarettes (p=0.003) and lowered substitution of smokeless tobacco products (p=0.028). In individuals who use multiple tobacco products, restrictions did not impact product purchasing.

CONCLUSION

Strategies to reduce flavored product sales and increase cessation resource accessibility may improve population health by reducing smoking and increasing NRT use in individuals who use menthol cigarettes.

Coolants, organic acids, flavourings and other additives that facilitate inhalation of tobacco and nicotine products: implications for regulation

To inform regulatory policy, this article summarises findings on inhalation facilitation from the ninth report of the WHO Study Group on Tobacco Product Regulation. Some additives counteract the harshness and bitterness of tobacco and nicotine product aerosols, making them easier to inhale. Additives that promote inhalability may perpetuate and increase the use of inhaled tobacco and nicotine products, especially by young people. Thus, as a class, additives that facilitate inhalation are an important regulatory target to prevent tobacco and nicotine product uptake. We defined inhalation facilitation as modifications to products during manufacturing that enhance the sensory experience and (potentially) behaviours associated with inhalation (eg, deeper puffs, faster inhalation, larger puff volume, shorter intervals in between puffs and use episodes). Evidence review showed that: (a) menthol and synthetic coolants decrease irritation caused by aerosol constituents by activating sensory perception receptors (eg, cooling receptors) and may promote dependence in inexperienced users; (b) acid additives and sugars, which lower the pH of aerosols and shift nicotine from free-base to protonated salt forms, reduce harshness and increase blood nicotine yield; (c) e-cigarette flavourings perceived as sweet or fruity reduce subjective bitterness, increase attractiveness and may escalate use, although their effects on perceived harshness are inconclusive; (d) sugars in tobacco impart sweet sensations, but limited industry-independent data preclude strong conclusions for sugars' roles in inhalation facilitation. Given these findings, WHO policy recommendations suggest that regulators might consider banning ingredients that facilitate inhalation in all commercial inhaled tobacco and nicotine products.

An analysis of flavor descriptors on tobacco products in the Philippines: Regulatory implications and lessons for low- and middle-income countries

BACKGROUND

Historically, tobacco companies have used flavored tobacco products to enhance the appeal of tobacco consumption, encourage initiation and experimentation of tobacco use, and contribute to sustained tobacco use. While flavored tobacco products are regulated in several countries, there is no existing regulation on flavored tobacco products in the Philippines, specifically for cigarettes and cigars. This study aims to update evidence on the flavored tobacco product landscape in the Philippines by assessing both the flavor descriptors and flavor imagery featured on cigarette and cigar packaging.

RESULTS

We collected 106 cigarette and cigar products from four major cities in the National Capital Region, Balanced Luzon, Visayas, and Mindanao. Of these 106 cigarette and cigar products, 62 (58.49%) had flavor descriptors. Three crushable capsule products did not feature any flavor descriptor but were included for flavor imagery examination. We identified five categories of flavor descriptors: menthol, concept descriptors, tobacco, beverages, and other flavors. Out of 62 packs, ten featured more than one flavor descriptor on the packaging. Menthol flavor descriptors comprised the majority of flavor descriptors. Imagery and other graphic elements closely resonate with and enhance the flavor descriptors found on these packs.

CONCLUSIONS

This study aimed to update the evidence on the flavored tobacco product landscape in the Philippines and address their absence of regulation. Regulating flavored tobacco products requires a comprehensive policy approach complemented by complete enforcement. Flavor substances, flavor descriptors, and flavor imagery must be regulated altogether; however, it is ideal to enforce a ban on flavored tobacco products in compliance with the WHO FCTC, to which the Philippines is a signatory. Policymakers should consider plain packaging as an intervention to eliminate the appeals associated with flavored tobacco products.

Characterizing the use, preferences, and perceptions of flavors in cigars in pregnant women

BACKGROUND

Flavors contribute to the appeal of tobacco products, but less is known about flavors in cigar products. The current study is the first to focus on characterizing the use and perceptions of flavors in cigar products among pregnant women.

METHODS

Pregnant women (N = 124) reported their use, preferences (liking, attractiveness, smoothness, interest), perceptions of harm (general, pregnancy-specific, fetal), and postpartum intention to use eight flavor categories (menthol/mint, spices, fruit, chocolate, alcohol, other beverages, candy/sweet, tobacco). We utilized correspondence analysis of contingency tables to investigate clustering of preferences and perceptions of flavors across the sample, and examined how preferences and perceptions of flavors may differ based on history of cigar use (none vs. lifetime vs. prenatal).

RESULTS

Overall, 37% reported never trying cigars, 51% reported lifetime use, and 12% reported prenatal use. Fruit (37%), tobacco (36%), and alcohol (14%) were the most common cigar flavors participants reported ever trying. Correspondence analysis revealed clustering in preferences for alcohol, fruit, and candy flavors compared to other flavors, and revealed lower intentions to use menthol/mint and tobacco flavors compared to other flavors. Participants who reported prenatal cigar use also reported more positive perceptions and greater intentions to use (1) spice and alcohol flavors compared to those who reported lifetime use (ps < .05); and (2) spice, alcohol, fruit, and tobacco cigar flavors compared to participants reporting never using cigars (ps < .04).

CONCLUSIONS

Regulations to restrict the availability of flavors, especially fruit, spice, and alcohol, may reduce the appeal and use of cigar products in pregnant women.

Selective Reduction of Socioeconomic Disparities in the Experimental Tobacco Marketplace: Effects of Cigarette and E-cigarette Flavor Restrictions

INTRODUCTION

Cigarette smoking accounts for >30% of the socioeconomic gap in life expectancy. Flavored restrictions claim to promote equity; however, no previous studies have compared the effect of cigarette and e-cigarette flavor restrictions among individuals who smoke with lower and higher socioeconomic status (SES).

AIMS AND METHODS

In a between-group within-subject design, individuals with lower (n = 155) and higher (n = 125) SES completed hypothetical purchasing trials in the experimental tobacco marketplace (ETM). Conditions were presented in a 2 × 2 factorial design (cigarette flavors restricted or unrestricted and e-cigarette flavors restricted or unrestricted) with increasing cigarette prices across trials.

RESULTS

Results show (1) SES differences in cigarette, e-cigarette, and NRT purchases under unrestricted policies, with lower SES showing higher cigarette demand and lower e-cigarette and NRT substitution than higher SES, (2) cigarette restrictions decreased cigarette and increased NRT purchases among lower SES, but no significant changes among higher SES, (3) decreased SES differences in cigarette demand under cigarette restrictions, but persistence under e-cigarette restrictions or their combination, (4) persistence of SES differences in e-cigarette purchases when all restrictions were enforced, and (5) waning of SES differences in NRT purchasing under all restrictions.

CONCLUSIONS

Flavor restrictions differentially affected individuals based on SES. Within-group comparisons demonstrated restrictions significantly impacted lower SES, but not higher SES. Between-group comparisons showed SES differences in cigarette purchasing decreased under cigarette restrictions, but persisted under e-cigarette-restrictions or their combination. Additionally, SES differences in NRT substitution decreased under flavor restrictions. These findings highlight the utility of the ETM to investigate SES disparities.

IMPLICATIONS

With increasing trends of socioeconomic differences in smoking prevalence and cessation rates, smoking-related health disparities are expected to continue to widen. Restricting menthol flavor in cigarettes while enhancing the availability and affordability of NRT have the potential to alleviate SES disparities in tobacco use, therefore, positively impacting health equity. However, this effect may depend on flavor availability in other tobacco products.

Reducing attractiveness of e-liquids: proposal for a restrictive list of tobacco-related flavourings

OBJECTIVE

Electronic cigarettes are addictive and harmful, and flavour is a key factor determining their abuse liability. Both adult smokers and young non-smokers like sweet and fruity flavours in particular. In order to discourage e-cigarette use among youth, the Dutch government announced in 2020 to only allow tobacco flavours in e-liquids. We propose a restrictive list of flavourings that will only enable the production of e-liquids with a tobacco flavour.

METHODS

We used e-liquid ingredient data notified via the European Common Entry Gate system before the government's announcement. First, we classified all e-liquids into flavour categories, and continued with the set of flavourings present in tobacco e-liquids. Five selection criteria related to prevalence of use, chemical composition, flavour description and health effects were defined to compile a restrictive list of tobacco flavourings.

RESULTS

E-liquids marketed as having tobacco flavour contained 503 different flavourings, some with tobacco flavour, but also other (such as sweet) flavours. We excluded (1) 330 flavourings used in <0.5% of e-liquids, (2) 77 used less frequently in tobacco than in all e-liquids, (3) 13 plant extracts, (4) 60 that are sweet or not associated with a tobacco flavour and (5) 7 flavourings with hazardous properties. This resulted in a final list of 16 flavourings.

CONCLUSIONS

Implementing this restrictive list will likely discourage e-cigarette use among youth, but could also make e-cigarettes less attractive as smoking cessation aid.

Correlation study on microbial communities and volatile flavor compounds in cigar tobacco leaves of diverse origins

To elucidate the significant influence of microorganisms on geographically dependent flavor formation by analyzing microbial communities and volatile flavor compounds (VFCs) in cigar tobacco leaves (CTLs) obtained from China, Dominica, and Indonesia. Microbiome analysis revealed that the predominant bacteria in CTLs were Staphylococcus, Aerococcus, Pseudomonas, and Lactobacillus, while the predominant fungi were Aspergillus, Wallemia, and Sampaiozyma. The microbial communities of CTLs from different origins differed to some extent, and the diversity and abundance of bacteria were greater than fungi. Metabolomic analysis revealed that 64 VFCs were identified, mainly ketones, of which 23 VFCs could be utilized to identify the geographical origins of CTLs. Sixteen VFCs with OAV greater than 1, including cedrol, phenylacetaldehyde, damascone, beta-damascone, and beta-ionone, play important roles in shaping the flavor profile of CTLs from different origins. Combined with the correlation analysis, bacterial microorganisms were more closely related to key VFCs and favored a positive correlation. Bacillus, Vibrio, and Sphingomonas were the main flavor-related bacteria. The study demonstrated that the predominant microorganisms were essential for the formation of key flavor qualities in CTLs, which provided a theoretical reference for flavor control of CTLs by microbial technology. KEY POINTS: • It is the high OAV VFCs that determine the flavor profile of CTLs. • The methylerythritol phosphate (MEP) pathway and the carotenoid synthesis pathway are key metabolic pathways for the formation of VFCs in CTLs. • Microbial interactions influence tobacco flavor, with bacterial microorganisms contributing more to the flavor formation of CTLs.

Menthol and Other Flavor Chemicals in Cigarettes from Vietnam and the Philippines

INTRODUCTION

Tobacco product flavors can increase product appeal, adolescent initiation and experimentation, and difficulty quitting. Flavored tobacco products are not restricted in Vietnam or the Philippines despite the high smoking prevalence among those 15 years of age and older (24% and 23%, respectively). There are no published reports to our knowledge on the levels of flavor chemicals in the cigarettes sold in these two countries.

METHODS

Cigarettes were purchased in Vietnam (32 brand variants) and the Philippines (19 brand variants) during 2020. Chemical analyses gave the mg/filter, mg/rod, and mg/stick (= mg/(filter + rod)) values for 180 individual flavor chemicals. Values were calculated for menthol, clove-related compounds, and "other flavor chemicals" (OFCs).

RESULTS

Five flavor groupings were found among the brand variants purchased in Vietnam: menthol + OFCs (n = 15), OFCs only (n = 8), nonflavored (n = 7), menthol + OFCs with a clove flavorant (n = 1) and menthol only (n = 1). Three flavor groupings were found among the brand variants purchased in the Philippines: menthol + OFCs (n = 10), nonflavored (n = 5), and menthol only (n = 4).

CONCLUSIONS

A range of flavored cigarette products are being offered by tobacco companies in Vietnam and the Philippines, presumably to maximize cigarette sales. Regulation of flavor chemicals should be considered in these two countries.

IMPLICATIONS

Article 9 of the WHO Framework Convention on Tobacco Control (FCTC), ratified by both Vietnam and the Philippines, states that "there is no justification for permitting the use of ingredients, such as flavoring agents, which help make tobacco products attractive." Flavors increase product appeal, adolescent initiation and experimentation, and difficulty quitting. These analyses found that cigarettes purchased in Vietnam and the Philippines contained menthol and other flavor chemicals. Tobacco companies are offering multiple flavor chemical profiles and nominally nonflavored versions in these countries; regulation of flavor chemicals should be considered in these two countries.

An ingredient co-occurrence network gives insight into e-liquid flavor complexity

INTRODUCTION

Part of the appeal of e-cigarettes lies in their available flavors. To achieve attractive flavors, e-liquids contain many different flavoring agents, which allow many flavoring combinations. To advance our knowledge of e-liquid flavors and compositions and to evaluate the effect of legislation, we determined whether there are ingredient combinations that are frequently used together.

METHODS

We used e-cigarette ingredient data from the European Common Entry Gate system (EU-CEG) as available on 31 December 2022.

RESULTS

In e-liquids, we found 214 ingredient pairs with a co-occurrence odds ratio greater than 10. Together, these consisted of 62 unique ingredients. Network analysis revealed that ingredients were grouped together based on their flavor and/or chemical structure. We identified two densely connected regions (clusters) in the network. One consisted of six ingredients with sweet-vanilla-creamy flavors. The second cluster consisted of 13 ingredients. While some of these have fruity flavors, others, such as alkyl carboxylic acids and dimethyl sulfide, are known to have unpleasant flavors. Additional data and literature analyses indicated that alkyl carboxylic acids can contribute to a creamy and sweet-fruity taste, whereas dimethyl sulfide can contribute to a more refined fruity taste.

CONCLUSIONS

These results exemplify that the flavor of e-liquids is not just the sum of its parts. Big data analyses on product data can be used to detect such patterns, but expert knowledge and additional data are needed for further interpretation. Monitoring of e-liquid flavors as well as ingredients will remain important to regulate e-liquid product attractiveness.

Considerations of Sex and Gender in FDA Tobacco Regulation

This Viewpoint discusses how sex and gender subpopulations may be differentially affected by tobacco products and suggests that the FDA formulate regulations in clinically meaningful ways.

Strawberry Additive Increases Nicotine Vapor Sampling and Systemic Exposure But Does Not Enhance Pavlovian-Based Nicotine Reward in Mice

Nicotine is an addictive drug whose popularity has recently increased, particularly among adolescents, because of the availability of electronic nicotine devices (i.e., "vaping") and nicotine e-liquids containing additives with rich chemosensory properties. Some efforts to understand the role of these additives in nicotine reward suggest that they increase nicotine reward and reinforcement, but the sensory contributions of additives, especially in their vapor forms, are largely untested. Here, to better understand how a fruit-flavored (i.e., strawberry) additive influences nicotine reward and aversion, we used a conditioned place preference (CPP) procedure in which nicotine and a strawberry additive were delivered as a vapor to male and female adolescent mice. We found that nicotine vapor alone can lead to a dose-dependent CPP when using a biased design. The strawberry additive did not produce CPP on its own, and we did not observe an effect of the strawberry additive on nicotine vapor-induced reward. Nevertheless, mice exposed to nicotine plus strawberry additive vapor had higher plasma cotinine concentrations, which did not appear to reflect altered nicotine metabolism. Instead, by directly measuring vapor sampling through respiration monitoring, we uncovered an increase in the amount of sniffing toward strawberry-containing nicotine vapor compared with nicotine vapor alone. Together these data indicate that chemosensory-rich e-liquid additives may enhance the perceived sensory profile of nicotine vapors rather than the reward value per se, which leads to overall increased nicotine exposure.

The interactive effects of JUUL flavor and nicotine concentration on addiction potential

Prior research suggests that flavors can influence the pharmacological effects of nicotine. We used commercially available JUUL pods to examine whether preferred menthol versus tobacco flavor increased the addictive potential of nicotine per se. This study recruited 15 regular JUUL e-cigarette users to complete a 2 × 2 factorial crossover trial using an entirely remote video format. Participants completed a sampling baseline session to identify preferred JUUL flavor (menthol vs. tobacco) followed by four counterbalanced experimental sessions separated by ≥ 48 hr: (a) low-nicotine dose (3% JUUL)/nonpreferred flavor; (b) low dose/preferred flavor; (c) high-nicotine dose (5% JUUL)/nonpreferred flavor; and (d) high dose/preferred flavor. In each experimental session, participants completed a puffing procedure followed by subjective ratings of e-cigarette liking and wanting (ELW), urges, and reinforcement using a JUUL pod purchase task. There was a dose-by-flavor interaction for average ELW (F = 4.58, p = .041) in which ELW was significantly greater for the preferred than the nonpreferred flavor at the low-nicotine dose but not the high-nicotine dose. There were also dose-by-flavor interactions for pre- to post-puffing change in overall urge to vape (F = 5.97, p = .021) and urge strength (F = 4.96, p = .049), with greater reductions in overall urge/strength for the preferred compared to the nonpreferred flavor at the low but not the high dose. We found no significant interaction effects for purchase task outcomes. Using a fully remote experimental puffing procedure, our findings suggest preferred flavors increase the rewarding effects most for lower nicotine e-cigarettes. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Elucidating the reinforcing effects of nicotine: a tribute to Nadia Chaudhri

Nadia Chaudhri worked with us as a graduate student in the Center for Neuroscience at the University of Pittsburgh from 1999 until she earned her PhD in 2005, a time that coincided with the discovery in our lab of the dual reinforcing actions of nicotine, a concept that she played an important role in shaping. The research that was described in her doctoral thesis is among the foundational pillars of the now well-accepted notion that nicotine acts as both a primary reinforcer and an amplifier of other reinforcer stimuli. This reinforcement-enhancing action of nicotine is robust and likely to be a powerful driver of nicotine use. Below, we discuss the evidence that these two actions of nicotine - primary reinforcement and reinforcement enhancement - are distinct and dissociable, a finding that Nadia was closely associated with. We go on to address two other topics that greatly interested Nadia during that time, the generalizability of the reinforcement-enhancing action of nicotine to multiple classes of reinforcing stimuli and potential sex differences in the dual reinforcing actions of nicotine. The research has greatly expanded since Nadia's involvement, but the core ideas that she helped to develop remain central to the concept of the dual reinforcing actions of nicotine and its importance for understanding the drivers of nicotine use.

Predictors of electronic cigarette dependence among non-smoking electronic cigarette users: User behavior and device characteristics

INTRODUCTION

ECIGs differ in their ability to deliver nicotine to the user and, consequently, they may differ in their ability to produce dependence. This study examined individual device characteristics, device type, and user behaviors as predictors of ECIG dependence in a sample of never-smoking ECIG users.

METHODS

Participants (N = 134) completed an online survey that assessed demographics, ECIG use behavior, and ECIG dependence as measured via the Penn State Electronic Nicotine Dependence Index (PSECDI) and E-cigarette Dependence Scale (EDS-4). Participants uploaded a picture of their personal ECIG device/liquid, which was coded by raters to identify product features. Multivariable linear regressions examined device characteristics (e.g., adjustable power, nicotine concentration) and device type (e.g., vape pen, mod, pod, modern disposable) as predictors of dependence controlling for demographics and user behaviors (e.g., ECIG use duration and frequency, other tobacco use).

RESULTS

Longer durations of ECIG use and more use days/week were associated significantly with higher PSECDI (β's = 0.91 and 1.90, respectively; p's < 0.01) and EDS-4 scores (β's = 0.16 and 0.28, respectively; p's < 0.01). Higher nicotine concentrations were associated with higher PSECDI scores only (β = 0.07, p =.011). Dependence scores did not differ as a function of ECIG device types after controlling for covariates.

CONCLUSIONS

ECIG dependence was observed among the never-smoking ECIG users in this sample, regardless of their ECIG device/liquid features. Findings suggest that regulatory efforts aimed at reducing the dependence potential of ECIGs in never smokers should focus on overall nicotine emissions rather than product features.

E-cigarette Flavors, Sensory Perception, and Evoked Responses

The chemosensory experiences evoked by flavors encompass a number of unique sensations that include olfactory stimuli (smell), gustatory stimuli (taste, i.e., salty, sweet, sour, bitter, and umami (also known as "savoriness")), and chemesthesis (touch). As such, the responses evoked by flavors are complex and, as briefly stated above, involve multiple perceptive mechanisms. The practice of adding flavorings to tobacco products dates back to the 17th century but is likely much older. More recently, the electronic cigarette or "e-cigarette" and its accompanying flavored e-liquids emerged on to the global market. These new products contain no combustible tobacco but often contain large concentrations (reported from 0 to more than 50 mg/mL) of nicotine as well as numerous flavorings and/or flavor chemicals. At present, there are more than 400 e-cigarette brands available along with potentially >15,000 different/unique flavored products. However, surprisingly little is known about the flavors/flavor chemicals added to these products, which can account for >1% by weight of some e-liquids, and their resultant chemosensory experiences, and the US FDA has done relatively little, until recently, to regulate these products. This article will discuss e-cigarette flavors and flavor chemicals, their elicited responses, and their sensory effects in some detail.

The Role of Nicotine and Flavor in the Abuse Potential and Appeal of Electronic Cigarettes for Adult Current and Former Cigarette and Electronic Cigarette Users: A Systematic Review

INTRODUCTION

Many adult cigarette smokers use electronic cigarettes (e-cigarettes) to cut down on or quit smoking cigarettes. E-cigarettes with higher abuse potential and appeal might facilitate complete switching. E-liquid nicotine concentration and flavor are two of the characteristics that may affect the abuse potential and appeal of e-cigarettes. The objective of this systematic review was to compile results from survey, animal, human laboratory, and clinical studies to understand the possible effects of nicotine concentration and flavor on abuse potential and appeal of e-cigarettes in adult current and former cigarette and e-cigarette users.

AIMS AND METHODS

A comprehensive literature search was conducted in Ovid Medline and PsycINFO followed by citation tracking in Web of Science Core Collection. Peer-reviewed studies published in English between 2007 and August 2020 were selected that analyzed differences between e-liquid nicotine concentration and/or flavors, had outcome measures related to abuse potential and/or appeal, and included adult humans (18+) or animals. A total of 1624 studies were identified and screened. A qualitative synthesis of results was performed.

RESULTS

Results from 104 studies included in this review suggest that higher nicotine concentration and access to a variety of flavors are likely to be associated with higher abuse potential and appeal of e-cigarettes for adult current and former cigarette and e-cigarette users.

CONCLUSIONS

Higher nicotine concentrations and the availability of a variety of flavors in e-cigarettes might facilitate complete substitution for cigarettes. Future e-cigarette regulations should take into account their impact on smokers, for whom e-cigarettes may be a cessation tool or reduced-harm alternative.

IMPLICATIONS

E-cigarettes may provide a reduced-harm alternative to cigarettes for smokers unwilling/unable to quit or serve as a path for quitting all nicotine products. Higher nicotine concentrations and flavor variety are associated with higher abuse potential and appeal of e-cigarettes. Higher abuse potential and appeal products may help facilitate complete switching from cigarettes to e-cigarettes. Regulation of nicotine concentration and flavors aimed at decreasing naïve uptake may inadvertently decrease uptake and complete switching among smokers, reducing the harm reduction potential of e-cigarettes. Evidence-based effects of regulating nicotine concentration and flavors must be considered for the population as a whole, including smokers.

Flavor science in the context of research on electronic cigarettes

Thousands start smoking or vaping daily, despite long-standing efforts by public health authorities to curb initiation and use of nicotine containing products. Over the last 15 years, use of electronic nicotine delivery systems has increased dramatically, with a diverse range of products on the market, including pod-based, disposable, and refillable electronic cigarettes (eCigs). Originally intended for harm reduction and smoking cessation, eCigs may encourage nicotine use among never smokers, given the vast range of appealing flavors that are available. To better understand abuse liability and to facilitate appropriate regulations, it is crucial to understand the science of flavor, and flavor perception within the context of eCig use. Here, we (a) provide a brief primer on chemosensory perception and flavor science for addiction and nicotine researchers, and (b) highlight existing some literature regarding flavor and nicotine use, with specific attention given to individual differences in perception, and interaction between different sensory modalities that contribute to flavor. Dramatic increases in use of eCigs highlights the importance of flavor science in contemporary addiction research, both with regards to public health and regulatory efforts. Other recent work summarizes findings on flavored e-liquids and eCig use, but none have focused explicitly on chemosensory processes or flavor perception as they relate to appeal and use of such products. We argue flavor science needs to be considered as perceptual and behavioral phenomena, and not merely from analytical, toxicological and pharmacological perspectives; we help address this gap here.

Chemosensory Contributions of E-Cigarette Additives on Nicotine Use

While rates of smoking combustible cigarettes in the United States have trended down in recent years, use of electronic cigarettes (e-cigarettes) has dramatically increased, especially among adolescents. The vast majority of e-cigarette users consume "flavored" products that contain a variety of chemosensory-rich additives, and recent literature suggests that these additives have led to the current "teen vaping epidemic." This review, covering research from both human and rodent models, provides a comprehensive overview of the sensory implications of e-cigarette additives and what is currently known about their impact on nicotine use. In doing so, we specifically address the oronasal sensory contributions of e-cigarette additives. Finally, we summarize the existing gaps in the field and highlight future directions needed to better understand the powerful influence of these additives on nicotine use.

Genotypic Differences in the Effects of Menthol on Nicotine Intake and Preference in Mice

Menthol has been shown to exacerbate elements of nicotine addiction in humans and rodents; however, the mechanisms mediating its effects are not fully understood. This study examined the impact of genetic factors in menthol’s effects on oral nicotine consumption by comparing two inbred mouse strains with differing sensitivities to nicotine. C57BL/6J (B6J) mice are nicotine-preferring, while DBA/2J (D2J) mice are not. While the effects of menthol on oral nicotine consumption have been highlighted in B6J mice, it is unknown if they extend to the D2J strain as well. Consequently, adolescent (PND 21) and adult (PND 63), male and female D2J mice were subjected to the nicotine two-bottle choice (2BC) paradigm with orally and systemically administered menthol. Then, we evaluated its impact on nicotine pharmacological responses in conditioned reward and nociception after systemic administration and, lastly, investigated the potential involvement of the TAAR1 gene and α7 nAChRs in menthol’s effects. Menthol failed to enhance oral nicotine consumption in adult and adolescent female and male D2J mice. Moreover, this lack in effect was not due to nicotine concentration, oral aversion to menthol, or basal preference for nicotine. Menthol also failed to augment nicotine reward or enhance nicotine-induced antinociception in D2J mice, demonstrating that genetic background plays a significant role in sensitivity to menthol’s effects on nicotine. Furthermore, TAAR1 or α7 nAChRs did not seem to mediate menthol’s differential effects in D2J mice. These findings support the existence of genotype-specific mechanisms that may contribute to the variable effects of menthol in different populations.

Internalizing problems are associated with initiation and past 30-Day use of flavored tobacco products

OBJECTIVE

Tobacco use remains disproportionately common among adults with internalizing problems. The rising prevalence of flavored tobacco use among this population may be a contributing factor. Using data from Wave 4 of the Population Assessment of Tobacco and Health Study, this study examined differences across adult ever tobacco users by severity of internalizing problems, in initiation of tobacco use with a flavored product and past 30-day (current) flavored tobacco use (n = 27,425). Severity of internalizing problems was measured using the Global Appraisal of Individual Needs-Short Screener Internalizing Disorder Screener. Tobacco use variables included initiation with or current use of a flavored product, assessed separately for each product. Weighted chi-square tests and multivariable modified Poisson regression models were used to examine the associations between severity of internalizing problems and each outcome.

RESULTS

Controlling for covariates, ever users with severe internalizing problems were more likely to have initiated with flavors for cigarettes (adjusted prevalence ratio [aPR]: 1.16, 95% confidence interval [CI]: 1.09,1.24), cigarillos (aPR: 1.09, 95% CI: 1.03, 1.16), electronic nicotine products (aPR: 1.08, 95% CI: 1.03, 1.13) and smokeless tobacco (aPR: 1.15, 95% CI: 1.04, 1.27), relative to those with low internalizing problems. Ever users with severe internalizing problems were more likely to currently use a flavored tobacco product for cigarettes (aPR: 1.15, 95% CI: 1.07, 1.24) and cigarillos (aPR: 1.15, 95% CI: 1.04, 1.28).

CONCLUSIONS

Flavored tobacco use seems disproportionately common among tobacco users with severe internalizing problems, across a variety of measures.

Open Characterization of Vaping Liquids in Canada: Chemical Profiles and Trends

Currently, there is a lack of comprehensive data on the diversity of chemicals present in vaping liquids. To address this gap, a non-targeted analysis of 825 vaping liquids collected between 2017 and 2019 from Canadian retailers was conducted. Prior to mass spectrometry analysis, samples were diluted 1:500 v/v with methanol or acetonitrile. Chemical compound separation and analysis was carried out using gas chromatography and triple quadrupole mass spectrometry (GC-MS/MS) systems operated in the full scan mode and mass range of 35-450 m/z. Mass spectrum for each sample was obtained in electron ionization at 70 eV and processed. Non-targeted identification workflow included use of automated mass spectral deconvolution and identification system (AMDIS), where required, as well as a number of commercially available spectral libraries. In order to validate identities, an in-house database of expected compounds previously detected in vaping liquids was used along with genuine analytical standards for compounds of interest. This resulted in a dataset of over 1,500 unique detected chemicals. Approximately half of these chemical compounds were detected only once in a single product and not in multiple products analyzed. For any sample analyzed, on average, 40% of the chemical constituents appeared to have flavouring properties. The remainder were nicotine and related alkaloids, processing, degradation or indirect additives, natural extractives and compounds with unknown roles. Data published here from the project on the Open Characterization of vaping liquids is unique as it offers a detailed understanding of products' flavour chemical profiles, the presence and frequency of chemicals of potential health concern, as well as trends and changes in products' chemical complexity over a three-year period. Non-targeted chemical surveillance such as this present valuable tools to public health officials and researchers in responding to emergent issues such as vaping associated lung injury or informing chemical based strategies which may be aimed at addressing product safety or appeal.

Exposure to fruit-flavoring during adolescence increases nicotine consumption and promotes dose escalation

The rise of e-cigarette popularity has sparked interest in the role of palatable flavors on nicotine use. Despite growing evidence that sweet flavorants enhance nicotine reward, their influence on nicotine consumption has not been studied extensively. In addition, the impact that flavored nicotine use in adolescence could have on nicotine reward and dependence in adulthood remains unclear. This study examined the role of flavored nicotine access on nicotine preference and consumption longitudinally, from adolescence to adulthood. Male and female adolescent mice preferred a fruit-flavored nicotine solution over an unflavored nicotine solution. However, only adolescent female mice with access to flavored nicotine consumed higher doses. Furthermore, while adolescent male mice escalated consumption of both flavored and unflavored nicotine, female mice only escalated nicotine consumption when given access to flavored nicotine. As mice matured into adulthood, there was no evidence that a history of flavored-nicotine access altered preference for unflavored nicotine compared to a nicotine-free control in a classic two-bottle choice design. However, when the nicotine concentration was progressively reduced, mice that had consumed strawberry-flavored nicotine in adolescence maintained baseline nicotine consumption levels longer than mice that initiated nicotine use without flavor in adolescence. Finally, addition of fruit-flavorants into the nicotine solution during adulthood led to nicotine preference and increased levels of nicotine consumption, regardless of previous flavored-nicotine access or of familiarity with the selected flavorant. These results indicate that flavorants increase nicotine consumption independent of life stage, possibly posing a disproportionate risk to adolescent females. Our results also point to an effect of adolescent flavored-nicotine use on nicotine dose maintenance in adulthood, which could have implications for the success of future quit attempts.

Flavor additives facilitate oral self-administration of nicotine solution in mice

RATIONALE

Tobacco products are very addictive, partly because they contain nicotine which is reinforcing, but also because they include appealing aromas and tastes. Flavor additives are such sensory stimuli which enhance attractiveness, as well as use and abuse of tobacco and vaping products. Yet, the interaction between these flavor additives and nicotine remains poorly understood.

OBJECTIVES

We want to understand how flavors may reduce nicotine' aversive taste and how it may enhance its voluntary oral self-administration in mice.

METHODS

We first studied the effect of flavor additives on nicotine solution palatability in a free bottle choice paradigm. Second, we investigated the effect of vanilla flavoring on the different stages of nicotine (40 μg/ml) oral self-administration in mice.

RESULTS

We show that adding flavors increase nicotine palatability and facilitate acquisition and maintenance of oral self-administration when compared to nicotine-alone group. Mice adapt their operant behavior depending on changes in nicotine concentration. All mice reinstate nicotine seeking upon presentation of associated cues. Nevertheless, vanilla-flavored nicotine was not more reinforcing than vanilla-flavored water which was reinforcing enough to drive similar operant response rates.

CONCLUSIONS

Flavor additives increase nicotine oral consumption and help maintaining operant behavior in mice. Moreover, flavors can be very attractive and can have high reinforcing value by themselves. Thus, it is crucial that the investigation on how taste signals play an important role in modulating oral nicotine intake in rodent models remains explored.

The impact of flavored ENDS use among adolescents on daily use occasions and number of puffs, and next day intentions and willingness to vape

BACKGROUND

The FDA's policies restricting sale of sweet flavored cartridge-based and disposable electronic nicotine delivery systems (ENDS) comprise important steps toward curbing adolescent ENDS use. However, additional evidence is needed about the contribution of specific flavors to adolescents' ENDS use. This study investigated the effects of flavor use on same day vaping behaviors, and next day intentions and willingness.

METHODS

We collected ecological momentary assessments (EMA) from 50 adolescent past two-week vapers (ages 14-17) over 14 days. Daily EMA data were collected on vaping occasions, total puffs, vaping intentions, vaping willingness, and flavor used.

RESULTS

On average, data were obtained on 13.4 days per participant (670 observations). Participants vaped flavors on 87% of days (fruit = 55%; mint = 30%; tobacco = 6%; menthol = 5%, and candy, sweets, or chocolate = 5%). On days when participants vaped fruit flavors, they took more puffs (r = 0.13, p = .030). On days when they vaped tobacco flavor, they reported more vaping occasions (r = 0.20, p = .005) and more puffs (r = 0.15, p = .033). On days when they vaped because of flavor appeal, they reported more vaping occasions (r = 0.19, p = .001) and more puffs (r = 0.24, p < .001). On days when they vaped menthol flavor, they were less likely to report willingness to vape the next day (r = -0.14, p = .042). Adolescents who reported vaping due to flavor appeal were more likely to report intentions (OR = 5.63, p = .035) and willingness to vape the next day (r = 0.23, p < .001) CONCLUSION: These findings provide additional support for policies restricting the sale of flavored ENDS products to adolescents.

5-HT2A and 5-HT2C receptors as potential targets for the treatment of nicotine use and dependence

Nicotine use and dependence, typically achieved through cigarette smoking, but increasingly through vape products, is the leading cause of preventable death today. Despite a recognition that many current smokers would like to quit, the success rate at doing so is low and indicative of the persistent nature of nicotine dependence and the high urge to relapse. There are currently three main forms of pharmacotherapy approved as aids to treat nicotine dependence: a variety of nicotine replacement products (NRT's), the mixed NA/DA reuptake inhibitor bupropion (Zyban®), and the preferential nicotinic α4β2 receptor agonist drug, varenicline (Chantix®); the latter being generally recognized to be the most effective. However, each of these approaches afford only limited efficacy, and various other pharmacological approaches are being explored. This chapter focusses on approaches targeted to the serotonin (5-HT) system, namely, selective serotonin reuptake inhibitors (SSRI's) which served a pioneer role in the investigation of serotoninergic modulators in human smoking cessation trials; and secondly drugs selectively interacting with the 5-HT2A and 5-HT2C receptor systems. From an efficacy perspective, measured as smoking abstinence, the 5-HT2A agonist psychedelics, namely psilocybin, seem to show the most promise; although as the article highlights, these findings are both preliminary and there are significant challenges to the route to approval, and therapeutic use of this class should they reach approval status. Additional avenues include 5-HT2C receptor agonists, which until recently was pioneered by lorcaserin, and 5-HT2A receptor antagonists represented by pimavanserin. Each of these approaches has distinct profiles across preclinical tests of nicotine dependence, and may have therapeutic potential. It is anticipated as diagnostic and predictive biomarkers emerge, they may provide opportunities for subject stratification and opportunities for personalizing smoking cessation treatment. The clinical assessment of SSRI, 5-HT2A and/or 5-HT2C receptor-based treatments may be best served by this process.