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Sensory and physiologic effects of menthol and non-menthol cigarettes with differing nicotine delivery.

Many smokers choose menthol-flavored cigarettes, however, the influence of menthol on the effects of smoke-delivered nicotine is unknown. Research and commercial cigarettes, menthol and non-menthol, that delivered a wide range of nicotine were evaluated. Menthol (n=18) and non-menthol (n=18) cigarette smokers participated in a single session during which three cigarettes were smoked 45 min apart, in random order. Federal Trade Commission (FTC) nicotine yields of the three cigarettes were: research, low yield, 0.2 mg, commercial cigarettes (average), 1.2 mg; research, high yield, 2.5 mg. Commercial and high-yield cigarettes increased heart rate (HR) and blood pressure more than low-yield cigarettes; although, no differences in exhaled carbon monoxide (CO) occurred. Participants smoked commercial cigarettes faster and with fewer puffs than either of the research cigarette indicating production differences can affect topography. There was a significant group by cigarette interaction on satisfaction, and relief from cigarette craving. High-yield non-menthol cigarettes reduced craving and were rated as more satisfying than high-yield menthol cigarettes. No differences between menthol and non-menthol cigarettes on other subjective measures (strength, psychological reward, negative effects) were observed. Our findings indicate that nicotine delivery, but not mentholation, influences cardiovascular and most subjective measures. These results illustrate the importance of threshold levels of nicotine on subjective responses to cigarette smoking.

Adult↗

Enantiomeric analysis of (+)-menthol and (-)-menthol by fluorogenic derivatization and liquid chromatography.

A simple and sensitive liquid chromatography is described for the quantitative analysis of enantiomeric (+)-menthol and (-)-menthol that are lack of chromophore. The method is based on the derivatization of (+)-menthol and (-)-menthol with a fluorescent reagent, naproxen acyl chloride, in toluene. The resulting diastereomic derivatives were separated on a C8 column with methanol-water-tetrahydrofuran (80:18:2, v/v) as a mobile phase; they were sensitively monitored with a fluorimetric detector (excitation 235 nm and emission 350 nm). The linear range for the quantitation of the enantiomers was 5.0-50 microM with a detection limit (signal to noise ratio = 3, injected volume 10 microl) of about 1 microM. Application of the method to the enantiomeric analysis of menthol in mint plants proved simple and feasible. Toluene was used for the extraction of menthol from the leaves of mint, and the resulting toluene extract was directly used for subsequent derivatization without solvent replacement.

Chromatography, High Pressure Liquid↗

Positive correlation between menthol content and in vitro menthol tolerance in Mentha arvensis L. cultivars.

Menthol is a highly valued monoterpene produced by Japanese mint (Mentha arvensis) as a natural product with wide applications in cosmetics, confectionery, flavours, beverages and therapeutics. Selection of high menthol yielding genotypes is therefore the ultimate objective of all genetic improvement programmes in Mentha arvensis. A positive correlation was observed in the present study between menthol content in oils of evaluated genotypes and the level of tolerance to externally supplied menthol of explants of these genotypes in culture medium. The easy use of this relationship as a selectable biochemical marker opens the practical applicability of large scale in vitro screening of the germplasm, clones and breeders' material for selection of elite genotypes.

Drug Resistance↗

Determination of menthol and menthol glucuronide in human urine by gas chromatography using an enzyme-sensitive internal standard and flame ionization detection.

The rate of peppermint oil absorption and excretion, following peroral administration, was determined by measuring urinary levels of menthol glucuronide. Menthol, a major component of peppermint oil, was liberated from its glucuronide metabolite by treating raw urine with beta-D-glucuronidase (Patella vulgata). Phenyl glucuronide was employed as an enzyme-sensitive internal standard. Menthol and phenol were recovered by ethyl acetate extraction and quantitated by capillary gas chromatography using flame ionization detection. Standard curves were linear between 25 and 250 micrograms/ml with a detection limit (signal-to-noise ratio = 2) of 0.25 microgram/ml. Assay precision was shown to be +/- 1.2% relative standard deviation.

Chromatography, Gas↗

Disposition kinetics and effects of menthol.

BACKGROUND: Menthol is widely used in a variety of commercial products and foods, but its clinical pharmacology is not well studied. To determine the disposition kinetics and to examine subjective and cardiovascular effects of menthol, we conducted a crossover placebo-controlled study that compared pure menthol versus placebo, along with an uncontrolled exposure to menthol in food or beverage. A novel assay for the measurement of menthol in biological fluids was also developed. METHODS: Twelve subjects were studied; each received a 100 mg l-menthol capsule, a placebo capsule, and 10 mg menthol in mint candy or mint tea on three different occasions. Plasma and urine levels of menthol and conjugated menthol (glucuronide), cardiovascular measurements, and subjective effects were measured at frequent intervals. RESULTS: Menthol was rapidly metabolized, and only menthol glucuronide could be measured in plasma or urine. The plasma half-life of menthol glucuronide averaged 56.2 minutes (95% confidence interval [CI], 51.0 to 61.5) and 42.6 minutes (95% CI, 32.5 to 52.7) in menthol capsule and mint candy/mint tea conditions, respectively (P < .05). The plasma area under the plasma concentration-time curve ratios for menthol capsule to mint candy/mint tea treatment averaged 9.2 (95% CI, 8.2 to 10.1). Urinary recovery of menthol as the glucuronide averaged 45.6 and 56.6% for menthol capsule and mint candy/tea, respectively (difference not significant). After menthol capsule dosing, the decrease in heart rate was less than the decrease after placebo administration (P < .05). Menthol reduced subjective vigor value at 30 minutes. CONCLUSIONS: We conclude that pure menthol and menthol in food or beverages have a similar systemic bioavailability and that menthol has a small cardioaccelerating effect.

Adult↗

Menthol pharmacology and its potential impact on cigarette smoking behavior.

Menthol is the only tobacco additive promoted and advertised by the tobacco industry. Although a considerable body of research has examined the effects of menthol when it is administered alone and unburned, the effects of menthol when burned in cigarette smoke are more complex because it is administered in a matrix of more than 4,000 substances. Therefore, it is difficult to isolate potential pharmacological and toxic effects of menthol when it is administered in a smoke mixture. Menthol properties include cooling and local anesthesia, as well as effects on drug absorption and metabolism, bronchodilation and respiration changes, and electrophysiology. Subjective effects of smoothness and less harshness have been identified as reasons for menthol cigarette smoking, but findings have been inconclusive regarding the effect of menthol on carbon monoxide exposure and smoking topography parameters. Gaps in the research literature and future research areas include the following: (a) What is the role of menthol in tobacco reinforcement and addiction? (b) In the absence of nicotine, is menthol reinforcing? (c) Are the pharmacological and physiological effects of menthol mediated by a menthol-specific receptor or some other central nervous system-mediated action? (d) What are the influences of menthol and menthol metabolism on the metabolic activation and detoxification of carcinogens in tobacco smoke? and (e) Do differences exist in cigarette smoking topography in relation to the interaction of ethnicity, gender, and menthol cigarette preference? Answers to these questions will help to elucidate the function of menthol in cigarettes and its impact on smoking behavior.

Behavior, Addictive↗

Does menthol attenuate the effect of bupropion among African American smokers?

BACKGROUND: African Americans have higher tobacco-related morbidity and mortality and are more likely to smoke menthol cigarettes than their white counterparts. This study examined differences between African American menthol and non-menthol smokers in smoking characteristics and cessation. METHODS: The study sample consisted of 600 African American smokers enrolled in a clinical trial that assessed the efficacy of sustained-release bupropion for smoking cessation. Menthol (n = 471) and non-menthol (n = 129) smokers were compared on smoking-related characteristics and abstinence rates at 6 weeks and 6 months. RESULTS: Menthol smokers were younger (41.2 versus 52.9 years), more likely to be female (73.7% versus 56.6%) and more likely to smoke their first cigarette within 30 minutes of waking up (81.7% versus 69.8%) compared to non-menthol smokers (all P < 0.01). Cigarette taste (50% versus 40%, P = 0.054) was rated non-significantly higher by menthol smokers. Seven-day point-prevalence abstinence from smoking at 6 weeks were 28% and 42% (P = 0.006) and at 6 months were 21% and 27% (P = 0.21) for menthol and non-menthol smokers, respectively. At 6 weeks follow-up, stepwise logistic regression revealed that among those younger than 50 years, non-menthol smokers were more likely to quit smoking (odds ratio = 2.0; 95% CI = 1.03-3.95) as were those who received bupropion (odds ratio = 2.12; 95% CI = 1.32-3.39). CONCLUSION: African American menthol smokers had lower smoking cessation rates after 6 weeks of treatment with bupropion-SR, thereby putting menthol smokers at greater risk from the health effects of smoking. Lower overall cessation rates among African Americans menthol smokers may partially explain ethnic differences in smoking-related disease risks.

Adult↗

Little evidence that "denicotinized" menthol cigarettes have pharmacological effects: an EEG/heart-rate/sujective-response study.

RATIONALE: A substantial portion of cigarette smokers prefer menthol-flavored cigarettes. To date, however, no studies have examined whether menthol in cigarettes has central pharmacological effects. OBJECTIVE: We investigated psychophysiological and subjective effects of smoking menthol versus non-menthol cigarettes in both menthol and non-menthol smokers. To assess these effects independently of the immediate effects of nicotine, all cigarettes employed were "denicotinized" (FTC nicotine yield = 0.06 mg). METHODS: The psychophysiological measures were EEG and heart rate (HR). The subjective measures assessed mental alertness, muscular relaxation, anxiety/nervousness, and how much a participant wanted to smoke one of his usual brand of cigarettes. Menthol and non-menthol smokers participated in a single session in which each participant smoked both a menthol and a non-menthol denicotinized cigarette (order balanced across participants). The psychophysiological and subjective measures were recorded before and after smoking each cigarette. RESULTS: Out of 48 F-ratios spanning 22 analyses of variance involving the critical interaction between pre-/post-smoking and menthol/non-menthol cigarette, only one unambiguously fit a "pharmacological" pattern, a result indistinguishable from a type-I statistical error. We report evidence that menthol smokers may be chronically less aroused and more sensitive to the effects of nicotine than non-menthol smokers. CONCLUSIONS: We found little evidence that menthol in cigarettes has central pharmacological effects.

Adolescent↗

Possible effects on smokers of cigarette mentholation: a review of the evidence relating to key research questions.

Menthol (2-isopropyl-5-methyl-cyclohexan-1-ol) is used in food, pharmaceutical, and tobacco products. Despite its long usage history and GRAS status, scientific literature on effects of cigarette mentholation is limited. Because African-American men have high lung cancer rates and predominantly smoke mentholated cigarettes, and because menthol's cooling effect might affect puffing and smoke inhalation, possible adverse effects of cigarette mentholation have been suggested. We review the evidence on the effects of mentholation on smokers, and we also identify areas for further study. Five large epidemiological studies provide no evidence that cigarette mentholation increases lung cancer risk. Mentholation cannot explain the higher risk for lung cancer in African-American male smokers, who also predominantly smoke mentholated cigarettes. Limited data on other cancers also suggest no risk from mentholation. The scientific literature suggests that cigarette mentholation does not increase puff number or puff volume of smoked cigarettes, and has little or no effect on heart rate, blood pressure, uptake of carbon monoxide, tar intake or retention, or blood cotinine concentration. Mentholation has little effect on other smoke constituents, and no apparent effect on nicotine absorption, airway patency and smoking initiation, dependency or cessation. Any toxicological effects of cigarette mentholation on adult smokers are probably quite limited.

Adult↗

Capsaicin and neurokinin A-induced bronchoconstriction in the anaesthetised guinea-pig: evidence for a direct action of menthol on isolated bronchial smooth muscle.

1. For many years menthol has been used in the treatment of respiratory disorders although, a bronchodilator effect of menthol has yet to be described. Using the bronchoconstrictors capsaicin (acting via stimulating the release of neuropeptides from sensory afferents) and neurokinin A (NKA) we have raised airways resistance in the guinea-pig (GP) and studied the effect of menthol on both capsaicin and NKA-induced bronchoconstriction in vivo. In vitro the effect of menthol on acetylcholine (ACh) and KCl precontracted GP bronchi was also studied. 2. GP (n = 13) were anaesthetized (urethane 1.5 g kg-1, i.p.) and a bolus injection of capsaicin (7.5 micrograms ml-1, i.v.) or infusion of NKA (1 microgram min-1, i.v.) was given either in the presence of air (0.81 min-1) or air impregnated with menthol vapour (7.5 micrograms l-1) freely breathed from a tracheal cannula via a T-piece. Airways resistance (Raw) and ventilation were measured throughout. Bronchi of mean internal diameter (1029 + 73.6 microns; n = 24) were removed from GP (n = 16) and mounted in the Cambustion myograph. Bronchial rings were maximally precontracted with 80 mM KCl or 2 mM ACh. Relaxation due to a cumulative dose of menthol (1- 3000 microM) was measured. 3. Menthol produced a significant (P < 0.05) 51.3% reversal of the capsaicin-induced increase in Raw, and also inhibited the significant (P < 0.05) reduction in minute ventilation (Ve) associated with the capsaicin-induced increased in Raw. Menthol also caused a significant (P < 0.05) 41% reversal of the NKA-induced increase in Raw. The NKA-induced decrease in Ve was again significantly (P < 0.05) reversed with menthol inhalation. Menthol caused a significant (P < 0.001) dose-dependent relaxation of KCl and ACh precontracted bronchi. 4. We have shown that menthol attenuates both capsaicin and NKA-induced bronchoconstriction in vivo and relaxes KCl and ACh preconstricted bronchi in vitro. Menthol inhibition of NKA and capsaicin-induced bronchoconstriction could be, in part, explained by a direct action of menthol on bronchial smooth muscle.

Airway Resistance↗

Enhanced oral bioavailability of ibuprofen in rats by poloxamer gel using poloxamer 188 and menthol.

To improve the oral bioavailability of poorly water-soluble ibuprofen with poloxamer and menthol, the effects of menthol and poloxamer 188 on the aqueous solubility of ibuprofen were investigated. The dissolution and pharmacokinetic study of ibuprofen delivered by the ibuprofen-loaded preparations composed of poloxamer 188 and menthol were then performed. In the absence of poloxamer, the solubility of ibuprofen increased until the ratio of menthol to ibuprofen increased from 0:10 to 4:6 followed by an abrupt decrease in solubility above the ratio of 4:6, indicating that four parts menthol formed eutectic mixture with six parts ibuprofen. In the presence of poloxamer, the solutions with the same ratio of menthol to ibuprofen showed an abrupt increase in the solubility of ibuprofen. The poloxamer gel with menthol/ibuprofen ratio of 1:9 and higher than 15% poloxamer 188 showed the maximum solubility of ibuprofen, 1.2 mg/mL. The simultaneous addition of menthol and poloxamer 188 significantly improved the dissolution rates of ibuprofen from aqueous solution due to the ibuprofen solubility-improving effect of menthol in the presence of poloxamer. Furthermore, the ibuprofen-loaded preparation with menthol and poloxamer 188 gave significantly higher initial plasma concentrations, Cmax, and AUC of ibuprofen than did the preparation without menthol and poloxamer 188, indicating that the simultaneous addition of menthol and poloxamer 188 could improve the oral bioavailability of ibuprofen in rats. In modern pain management it is always desirable for the ibuprofen-loaded preparation with poloxamer 188 and menthol to show a rapid onset of action with a minimal phase of lag time to feel the decreased pain. From an industry point of view, it is more desirable for a formulation to be fast acting, easy to use, and cost effective. Thus, the ibuprofen-loaded preparation with poloxamer 188 and menthol was a more effective oral dosage form for poorly water-soluble ibuprofen.

Administration, Oral↗

Inhibition of human liver microsomal (S)-nicotine oxidation by (-)-menthol and analogues.

(-)-Menthol is a widely used flavoring ingredient present in mouthwash, foods, toothpaste, and cigarettes; yet, the pharmacological effects of menthol have not been widely studied. Mentholated cigarette smoking may increase the risk for lung cancer. Many African American smokers smoke mentholated cigarettes, and African Americans have a significantly higher incidence of lung cancer as compared with whites. There may be a relationship between the incidence of lung cancer and the type of cigarette smoked because the use of mentholated cigarettes by white smokers is significantly less and the incidence of lung cancer is less. The mechanism whereby (-)-menthol could increase the health risk of smoking is not known. The results of our in vitro studies herein show that (-)-menthol and synthetic congeners inhibit the microsomal oxidation of nicotine to cotinine and the P450 2A6-mediated 7-hydroxylation of coumarin. Replacement of the alcohol oxygen atom of menthol with other heteroatoms increased the potency of P450 2A6 inhibition. Thus, the K(i) value of (-)-menthol for inhibition of microsomal nicotine oxidation was 69.7 micro M but neomenthyl thiol possesses a K(i) value of 13.8 micro M. Menthylamine inhibited nicotine oxidation with a K(i) value of 49.8 micro M, but its hydroxylamine derivative gave an IC(50) value of 2.2 micro M. A series of 16 menthol derivatives and putative metabolites were procured or chemically synthesized and tested as inhibitors of P450 2A6. While highly potent inhibition of P450 2A6 was not observed for the menthol analogues examined, it is nevertheless possible that smoking mentholated cigarettes leads to inhibition of nicotine metabolism and allows the smoker to achieve a certain elevated dose of nicotine each day. This may be another example of self-medication to obtain the desired effect of nicotine.

Animals↗

Characterization of measured menthol in 48 U.S. cigarette sub-brands.

More than 25% of cigarettes sold in the United States are branded as mentholated, and these cigarettes are smoked disproportionately among populations with disparate tobacco-related health outcomes. This study is the first (independent of the tobacco industry) to report menthol for 48 popular commercially available mentholated cigarette sub-brands. The dependent variable "menthol per cigarette" was obtained by gas chromatography-mass spectrometer assay, whereas average per-cigarette milligram weight of tobacco filler ("tobacco per cigarette") was determined gravimetrically. Pearson's correlations assessed associations among continuous variables. Analyses of variance assessed mean differences on the independent variables of interest: manufacturer, brand family, industry descriptors of length (100 mm and King [85 mm]) and label (ultralight, light, medium/mild, and regular/full flavor), and a category constructed by the authors of exclusively menthol brand families (those without a non-menthol offering; Kool, Newport, and Salem) versus others (GPC, Camel, and Marlboro). Results showed menthol per cigarette and menthol per tobacco (i.e., milligrams of menthol per gram of tobacco filler) to be significantly greater in cigarettes labeled with industry descriptors of ultralight or light, belying the common consumer perception that "light" means less. Menthol per cigarette and tobacco per cigarette were significantly greater in 100-mm compared with 85-mm cigarettes. The study results are consistent with prior research that suggests menthol may be used to offset reductions in smoke delivery or impact and to facilitate compensatory smoke inhalation behaviors in smokers of cigarettes with reduced machine-measured smoke delivery. Tobacco manufacturers should be required by federal or other regulatory agencies to report the amount of menthol added to cigarettes.

Analysis of Variance↗