Acute effects of inhaled menthol on the rewarding effects of intravenous nicotine in smokers

The Effects of Changes in Cigarette Menthol Content on Acute Nicotine Pharmacology and Smoking Topography

INTRODUCTION

Menthol influences the appeal and addictiveness of cigarette smoking, however the data regarding menthol's effects on nicotine pharmacokinetics (PK) and smoking topography are inconsistent. This study investigated the impact of different cigarette menthol levels on nicotine pharmacology and smoking topography in current menthol smokers.

AIMS AND METHODS

The study was a double-blind, randomized, four-period, crossover study to investigate the effects of smoking cigarettes with varying menthol content (0, 3, 6, and 12 mg menthol) on nicotine PK, smoking topography, and subjective effects in current menthol smokers. Each experimental session consisted of a prescribed use session, followed by 145 min of no smoking and a 1-h ad libitum smoking session. Serial blood samples were collected; smoking topography was recorded using CReSS Lab topography device.

RESULTS

There was no significant effect of menthol on nicotine PK after prescribed smoking of cigarettes with varying menthol contents. During ad libitum smoking, there was significantly smaller total puff volume and puff duration in the 12 mg menthol condition compared to other menthol conditions. Subjective and sensory measures indicated significantly higher overall positive ratings for the 3 mg and 6 mg menthol cigarettes compared to the 0 mg menthol cigarette; the 12 mg menthol cigarette was less liked and harsher than the 3 mg condition.

CONCLUSIONS

These findings suggest that menthol, at concentrations reflecting the marketplace (3-6 mg), contributes to positive subjective smoking experiences among menthol smokers, but does not have a significant effect on nicotine PK or smoking topography in an acute laboratory setting.

IMPLICATIONS

While our data indicate that varying menthol content does not have a significant impact on nicotine's pharmacological effects under acute exposure conditions, these data highlight the contribution of menthol's flavor and sensory effects to product preference and positive smoking experiences, which facilitate repeated experimentation, progression to regular use, and subsequent dependence.

Commentary: Cigarette dependence in menthol and non-menthol young adult cigarette smokers

FDA's Proposed Final Rule to ban menthol cigarettes asserts that "menthol cigarettes contribute to greater nicotine dependence in youth and young adults than non-menthol cigarettes." However, none of the publications referenced included young adults. To provide empirical evidence on the subject, we examine smoking frequency and Heaviness of Smoking Index (HSI) dependence among 2,194 young adult (ages 18-25 years) menthol and non-menthol smokers from 31 online survey samples. Unpaired t-tests examined if daily smoking or the proportion of daily smokers who are low or high dependence on the HSI vary by menthol cigarette smoking status. Young adult menthol smokers were less likely to be daily smokers than young adult non-menthol smokers. There were no differences in the percentages of daily menthol and non-menthol smokers categorized as low or high dependence on the HSI. Smoking menthol cigarettes, therefore, does not appear to be associated with greater cigarette dependence among young adults than smoking non-menthol cigarettes.

Effects of mint, menthol, and tobacco-flavored e-cigarettes on tobacco withdrawal symptoms in adults who smoke menthol cigarettes: A laboratory pilot study

BACKGROUND

Menthol cigarette smoking has remained stable or increased in certain groups, despite an overall decline in cigarette smoking rates in the U.S. Understanding whether e-cigarettes alter patterns of menthol cigarette use is critical to informing efforts for reducing the public health burden of menthol cigarette smoking. This 2019-2020 laboratory pilot study evaluated whether self-administration of mint-, menthol-, or tobacco-flavored e-cigarettes would differentially impact tobacco withdrawal symptoms in e-cigarette-naïve adults who smoke menthol cigarettes daily.

METHODS

Participants (N=17; 35.3% Female; mean age=51.8) attended three laboratory sessions after 16-hours of tobacco abstinence. Participants self-administered a study-provided JUUL e-cigarette (0.7mL with 5% nicotine by weight) at each session in which flavor was manipulated (mint vs. menthol vs. tobacco; order randomized). Participants completed pre- and post-e-cigarette administration self-report assessments on smoking urges, nicotine withdrawal, and positive and negative affect states. Multilevel linear regression models tested differences between the three flavor conditions for individual study outcomes.

RESULTS

Following overnight tobacco abstinence, vaping either a mint or menthol (vs. tobacco) flavored e-cigarette led to significantly greater reductions in smoking urges over time; menthol (vs. tobacco) flavored e-cigarettes also suppressed urges to smoke for pleasure. Notably, no differences in nicotine withdrawal, positive affect, or negative affect were observed.

CONCLUSIONS

In this laboratory pilot study, mint and menthol (vs. tobacco) flavored e-cigarettes provided some negative reinforcement effects via acute reductions in smoking urges during tobacco abstinence, yet only menthol flavored e-cigarettes demonstrated suppressive effects on smoking urges for pleasure in adults who smoke menthol cigarettes daily.

Plasma Menthol Glucuronide as a Biomarker for the Behavioral Effects of Menthol and Nicotine in Humans

This secondary analysis sought to determine if plasma menthol glucuronide (MG) concentrations predict changes in three outcomes, subjective drug effects, urges to smoke, and heart rate, following concurrent inhaled menthol and intravenous nicotine. A total of 45 menthol and non-menthol cigarettes smokers (36 male, nine female, 20 Black, and 23 White) were included in this double-blind, placebo-controlled study. Across three test sessions, participants were assigned to a different flavor condition for each session: 0% (no menthol), 0.5%, or 3.2% menthol. In each test session, participants received in a random order one intravenous delivery of saline and two intravenous deliveries of nicotine (0.25 mg/70 kg and 0.5 mg/70 kg), each 1 h apart, concurrent with menthol delivery by e-cigarettes. The main outcomes were subjective drug effects, urges to smoke, and heart rate. The results showed that following e-cigarette inhalation, changes in plasma MG concentrations or “menthol boost” increased proportionally to the menthol concentration in the e-liquids. While changes in plasma MG concentrations were not predictive of increases in heart rate or subjective drug effects that are reflective of acute effects from nicotine (i.e., feel good effects, stimulated, aversive effects), they were predictive of cooling effect, a typical effect of menthol, but only in menthol smokers in the absence of concurrent active nicotine infusion. These findings demonstrate the utility of plasma MG as a biomarker both for acute menthol exposure by e-cigarette inhalation and for the examination of the concentration-dependent behavioral and physiological effects of menthol in humans.

The effects of inhaled flavors on intravenous nicotine

Menthol is the only available flavor in combusted tobacco cigarettes; however, e-cigarettes are available in thousands of flavors. Research on flavors and rewarding properties of nicotine is limited. The present study sought to examine the acute rewarding effects of flavors inhaled from an e-cigarette, in combination with intravenous (IV) nicotine among cigarette smokers. In the present study, 24 menthol-preferring young adult (aged 18 to 30) cigarette smokers were tested under 3 different e-cigarette flavor conditions (menthol, green apple, or menthol + green apple) in a within-subject cross-over design. During each test session, each participant received 3 IV infusions (saline, 0.25 mg/70 kg nicotine, 0.5 mg/70 kg nicotine) administered 1 hr apart. The main outcome measures assessed cardiovascular, subjective, and cognitive domains. Compared with green apple or green apple + menthol, menthol produced higher ratings of "cooling" (ps < 0.01). Craving was rated higher following administration of green apple and the combined menthol + apple flavor compared to menthol alone (ps < 0.05). As expected, IV-nicotine dose-dependently increased the ratings of subjective liking/disliking and peak heart rate, improved cognitive performance, and reduced smoking urges (all ps < 0.05). These subjective, cognitive, and physiological effects of nicotine were not affected by any flavor condition. The present findings did not support an interaction between IV-nicotine dose and inhaled flavor for acute effects of nicotine. Green apple flavor, alone or in combination with menthol, could result in higher craving or insufficiently alleviate craving, relative to menthol flavor alone. Additional research is warranted to examine extended exposure to inhaled flavors on the rewarding and addictive effects of nicotine. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Acute effects of inhaled menthol on cognitive effects of intravenous nicotine among young adult cigarette smokers

Basic science studies indicate that menthol can enhance the cognitive effects of nicotine to increase nicotine dependence; however, the effect of menthol and nicotine on cognitive functioning among humans has been understudied. This double-blind, placebo-controlled study examined the dose-dependent effects of inhaled menthol flavoring and intravenous nicotine on cognitive task performance. Twenty menthol (MS) and 18 non-menthol (NMS) cigarette preferring, young-adult smokers (21% female; 7.9% Hispanic, 44.7% Non-Hispanic/White, 47.4% Non-Hispanic/Black) completed three sessions with randomized order of menthol flavoring (between-sessions: 0.0%/tobacco control, 0.5%/low, 3.2%/high) and intravenous nicotine (within-session: 0.0 mg/saline control, 0.25 mg/low, 0.5 mg/high). After each administration, participants completed three cognitive tasks: Continuous Performance Task (CPT), Mathematical Processing Task (MPT), and Stroop Task. Mixed effects models were used to examine interactive effects of cigarette type preference and menthol and nicotine doses. MS vs. NMS had decreased accuracy on CPT and MPT and efficiency during Stroop. No significant effects of cigarette type preference by menthol or nicotine were found for any task. Significant effects of nicotine by menthol were found during Stroop, where participants had greater accuracy for high nicotine compared to saline during the low menthol session. Significant effects of menthol by timepoint were seen during Stroop, where participants improved across timepoints during the low menthol session. Findings did not support significant effects of inhaled menthol, alone or with nicotine, on cognitive performance. Further research clarifying the impact of varying menthol and nicotine levels in nicotine products may help to elucidate menthol's role in smoking sustainment.

Chemical analysis of fresh and aged Australian e-cigarette liquids

OBJECTIVES

To assess the chemical composition of electronic cigarette liquids (e-liquids) sold in Australia, in both their fresh and aged forms.

DESIGN, SETTING

Gas chromatography-mass spectrometry analysis of commercial e-liquids sold in Australia (online and physical stores).

MAIN OUTCOME MEASURES

Chemical composition of 65 Australian e-liquids - excipients/solvents, flavouring chemicals, other known e-liquid constituents (including nicotine), and polycyclic aromatic hydrocarbons - before and after an accelerated ageing process that simulated the effects of vaping.

RESULTS

The measured levels of propylene glycol and glycerol often diverged from those recorded on the e-liquid label. All e-liquids contained one or more potentially harmful chemicals, including benzaldehyde, menthol, trans-cinnamaldehyde, and polycyclic aromatic hydrocarbons. Nicotine or nicotyrine were detected in a small proportion of e-liquids at extremely low concentrations.

CONCLUSIONS

Australian e-liquids contain a wide variety of chemicals for which information on inhalation toxicity is not available. Further analyses are required to assess the potential long term effects of e-cigarette use on health.

Threshold dose for intravenous nicotine self-administration in young adult non-dependent smokers

RATIONALE

Reducing nicotine content of inhaled tobacco products may prevent nicotine addiction, but the threshold for nicotine reinforcement has not been systematically evaluated in controlled human laboratory studies.

OBJECTIVES

The current study uses a novel double-blind placebo-controlled intravenous (IV) nicotine self-administration (NSA) model to determine threshold for subjective effects of nicotine and nicotine reinforcement using a forced choice self-administration procedure.

METHODS

Young adults (n = 34) had 5 laboratory sessions after overnight nicotine abstinence. In each session, participants sampled and rated the subjective effects of an IV dose of nicotine (0.0125, 0.025, 0.05, 0.1, or 0.2 mg nicotine/70 kg bodyweight) versus saline (placebo), then were given a total of 10 opportunities to self-administer either the IV dose of nicotine or placebo.

RESULTS

Mixed effect models revealed a significant effect of nicotine dose for positive (i.e., "stimulatory" and "pleasurable"; p < .0001) effects, but not "aversive" effects during sampling period. Post hoc comparisons showed that higher doses (i.e., 0.1 and 0.2 mg) were associated with greater stimulatory, pleasurable, and physiological effects than placebo and lower doses. Mixed effect models revealed that only the highest dose (i.e., 0.2 mg) was consistently preferred over placebo. Sex differences were generally weak (p = .03-.05).

CONCLUSIONS

Using our IV nicotine NSA model, the threshold for detecting positive effects of nicotine in young adult smokers is about 0.1 mg, but a higher dose of nicotine, 0.2 mg, is required to produce a consistent nicotine reinforcement. Regarding the regulatory impact, our findings further support the value of nicotine reinforcement threshold as a tobacco regulatory target.

Differences in Cognitive Task Performance, Reinforcement Enhancement, and Nicotine Dependence Between Menthol and Nonmenthol Cigarette Smokers

INTRODUCTION

Menthol has been shown to target similar brain regions and neural receptors as nicotine, yet the association between menthol cigarette use and cognitive performance remains unknown.

AIMS AND METHODS

This study examined differences in cognitive task performance between menthol (MS) and nonmenthol (NMS) cigarette smokers after acute cigarette consumption. Sixty white and black and/or African American, nonabstinent, MS (n = 30) and NMS (n = 30) were assessed presmoking and postsmoking their preferred cigarette on four computerized tasks: Continuous Performance Task (CPT; alerting attention), N-Back Task (working memory), Finger Tapping Task (motor control), and Apple Picker Task (reinforcement enhancement). Self-reported nicotine dependence and objective smoking topography measures were also compared between groups.

RESULTS

Initial unadjusted analyses showed a significant effect of cigarette type × time on CPT speed (p = .042), where MS improved while NMS group worsened in CPT speed after smoking. After controlling for baseline cigarette craving and cigarette nicotine levels, the effect of cigarette type × time for all cognitive outcomes was statistically nonsignificant (ps > .05). However, there remained a significant effect of cigarette type, where MS versus NMS had poorer CPT (p = .046) and N-Back Task accuracy (p = .006) but faster N-Back speed (p = .039). There were no statistically significant differences between groups on reinforcement enhancement, nicotine dependence, or smoking behavior outcomes (ps > .05).

CONCLUSIONS

Contrary to our hypotheses, results did not find a significant effect of cigarette type on the change in cognitive performance after acute smoking in nonabstinent smokers. Further studies are needed to clarify the specific pharmacological effects of nicotine and menthol on cognitive functioning.

IMPLICATIONS

The current study is the first to compare the potential enhancement of cognitive task performance after acute cigarette smoking between satiated menthol and nonmenthol cigarette smokers. Study results suggest that acute menthol cigarette use may not enhance cognitive function above and beyond nonmenthol cigarettes to increase dependence among menthol smokers. However, the contribution of other psychological factors (eg, craving, mood) and cigarette characteristics (eg, nicotine content) may be involved in cognitive function enhancement to perpetuate dependence and smoking persistence for menthol smokers.

The Biological Impact of Menthol on Tobacco Dependence

In the 1920s, tobacco companies created a marketing campaign for what would one day be their most profitable series of products: mentholated tobacco cigarettes. Menthol provides the smoker with a pleasant mint flavor in addition to a cooling sensation of the mouth, throat, and lungs, giving relief from the painful irritation caused by tobacco smoke. Promising a healthier cigarette using pictures of doctors in white coats and even cartoon penguins, tobacco companies promoted these cigarettes to young, beginner smokers and those with respiratory health concerns. Today, smoking tobacco cigarettes causes one in five US Americans to die prematurely, crowning it as the leading cause of preventable death. In contrast to the dubious health claims by tobacco companies, mentholated cigarettes are in fact more addictive. Smokers of mentholated cigarettes have lower successful quit rates and in some cases are resistant to both behavioral and pharmacological treatment strategies. There is now considerable evidence, especially in the last 5 years, that suggest menthol might influence the addictive potential of nicotine-containing tobacco products via biological mechanisms. First, menthol alters the expression, stoichiometry, and function of nicotinic receptors. Second, menthol's chemosensory properties operate to mask aversive properties of using tobacco products. Third, menthol's chemosensory properties aid in serving as a conditioned cue that can both enhance nicotine intake and drive relapse. Fourth, menthol alters nicotine metabolism, increasing its bioavailability. This review discusses emerging evidence for these mechanisms, with an emphasis on preclinical findings that may shed light on why menthol smokers exhibit greater dependence.

IMPLICATIONS

Mentholated cigarettes have been shown to have greater addictive potential than their nonmentholated counterparts. Evidence is pointing toward multiple mechanisms of action by which menthol may alter tobacco dependence. Understanding menthol's biological functions as it pertains to nicotine dependence will be helpful in crafting novel pharmacotherapies that might better serve menthol smokers. In addition, a better understanding of menthol's pharmacology as it relates to tobacco dependence will be valuable for informing policy decisions on the regulation of mentholated cigarettes.

The Impact of Electronic Nicotine Delivery System (ENDS) Flavors on Nicotinic Acetylcholine Receptors and Nicotine Addiction-Related Behaviors

Over the past two decades, combustible cigarette smoking has slowly declined by nearly 11% in America; however, the use of electronic cigarettes has increased tremendously, including among adolescents. While nicotine is the main addictive component of tobacco products and a primary concern in electronic cigarettes, this is not the only constituent of concern. There is a growing market of flavored products and a growing use of zero-nicotine e-liquids among electronic cigarette users. Accordingly, there are few studies that examine the impact of flavors on health and behavior. Menthol has been studied most extensively due to its lone exception in combustible cigarettes. Thus, there is a broad understanding of the neurobiological effects that menthol plus nicotine has on the brain including enhancing nicotine reward, altering nicotinic acetylcholine receptor number and function, and altering midbrain neuron excitability. Although flavors other than menthol were banned from combustible cigarettes, over 15,000 flavorants are available for use in electronic cigarettes. This review seeks to summarize the current knowledge on nicotine addiction and the various brain regions and nicotinic acetylcholine receptor subtypes involved, as well as describe the most recent findings regarding menthol and green apple flavorants, and their roles in nicotine addiction and vaping-related behaviors.

Menthol additives to tobacco products. Reasons for withdrawing mentholated cigarettes in European Union on 20th may 2020 according to tobacco products directive (2014/40/EU)

Menthol, which is a natural cyclic monoterpene alcohol with a minty smell, is one of the main constituents of essential oils that naturally occur in some aromatic plants, such as Mentha × piperita L. This natural compound shows many biological properties, such as anesthetic, analgesic, antibacterial and antifungal, immunomodulating, and skin penetration-enhancing. It is added to a variety of goods, such as food, oral-care products, OTC products, cosmetics, and tobacco products. Menthol is not just a simple flavoring agent, especially when it comes to tobacco products. Its ability to 'mask' the negative effects of nicotine and its additional positive sensory effects makes it the most common additive in such products. For the customers, mentholated tobacco products may be mistakenly perceived as less harmful for health, which may increase their consumption. However, as the evidence shows, menthol cigarettes are no safer than conventional cigarettes and may lead to more frequent disease exacerbation during prolonged exposure to smoke from such products. In addition, because of its complex interactions with nicotine, menthol may affect smoking behavior and may increase addiction to nicotine. For those reasons, the European Union banned flavored cigarettes (whose sale size reached more than 3% of the total tobacco product market) by implementing the Tobacco Products Directive (2014/40/EU) on 20th May 2020. While the menthol ban was based on health concerns, the ultimate effect on consumers, regarding potential quitting, is yet to be determined.

Measures of dependence in menthol and nonmenthol smokers - A comprehensive narrative review

Introduction. More than a decade ago, concerns were raised that menthol in cigarettes might enhance addiction to smoking. This article provides a comprehensive review of published studies examining cigarette dependence among menthol and nonmenthol smokers. The purpose of the review is to evaluate the scientific evidence to determine if menthol increases cigarette dependence. Materials and Methods. The published literature was searched in 2019 for studies that provide evidence on cigarette dependence among menthol compared to nonmenthol smokers. Included in this review are published studies that compare menthol and nonmenthol smokers based on widely accepted and validated measures of dependence, or other established predictors of dependence (age of smoking initiation [first cigarette]/age of progression [regular/daily smoking]) and indicators of dependence (smoking frequency, cigarettes smoked per day, time to first cigarette after waking, night waking to smoke, smoking duration). Results and Conclusion. Based on a review of the available studies, including those with adjusted results and large representative samples, reliable and consistent empirical evidence supports a conclusion that menthol smokers are not more dependent than nonmenthol smokers and thus menthol in cigarettes does not increase dependence.

Effect of menthol on nicotine intake and relapse vulnerability in a rat model of concurrent intravenous menthol/nicotine self-administration

RATIONALE

Epidemiological data suggest that menthol may increase vulnerability to cigarette/nicotine use and relapse. While menthol's sensory properties are often attributed as the underlying cause of the enhanced vulnerability, an alternative possibility is that they are mediated via pharmacological interactions with nicotine.

OBJECTIVE

This study addressed the possibility that menthol enhances nicotine intake and relapse vulnerability via pharmacological interactions with nicotine using a concurrent intravenous menthol/nicotine self-administration procedure.

METHODS

Following acquisition, adolescent rats were given 23-h/day access to nicotine (0.01 mg/kg/infusion), nicotine plus menthol (0.16, 0.32, or 0.64 mg/kg/infusion), or menthol alone (0.16, 0.32, 0.64 mg/kg/infusion) for a total of 10 days. Nicotine-seeking was assessed using an extinction/cue-induced reinstatement procedure following 10 days of forced abstinence. We also assessed the effect of menthol (0.32 mg/kg/infusion) on progressive ratio responding for nicotine (0.01 mg/kg/infusion).

RESULTS

Menthol decreased PR responding for nicotine but did not affect self-administration under extended access conditions. The low dose of menthol tended to decrease subsequent extinction responding, and was not different from menthol alone, whereas the high dose decreased reinstatement responding. Although not significant, the highest levels of extinction responding were observed in a minority of rats in the moderate and high menthol-nicotine groups; rats in these groups also took longer to extinguish.

CONCLUSIONS

Taken together, these results demonstrate that pharmacological interactions of menthol with nicotine reduce, rather than increase, nicotine's reinforcing effects and some measures of relapse vulnerability. Importantly, however, moderate and high menthol doses may increase some aspects of relapse vulnerability in a minority of individuals.