A Comparison of Use Topography and Nicotine Pharmaco*kinetics Among Loose and Portioned Smokeless Tobacco Users (2024)

Search for other works by this author on:

Article history

Abstract

Introduction

Smokeless tobacco (ST) refers to tobacco products that are consumed by chewing, sucking, holding in the oral cavity, or sniffing, rather than smoking, and describes a heterogenous class of products used in 127 countries worldwide, with the highest prevalence of adult users in South and Southeast Asia.¹ In the United States, an estimated 2.4% of adults report current use (use in the past 30 days) of ST products, representing roughly 5.9 million adults.² Given that ST use is associated with nicotine dependence,³ and may lead to oral and pancreatic cancer,⁴ oral mucosal lesions,⁵ and periodontal disease and tooth loss,⁶ ST use is a serious public health concern.

Currently, moist snuff, the leading type of ST in the US market,⁷ is available in two distinct formats: loose and portioned. Loose moist snuff ST products (hereafter referred to as loose ST products) consist of cut tobacco leaves stored loosely in a container (eg, can). Loose ST users take a “pinch” of moist snuff from the can and place it in the mouth between the cheek and gum. Portioned moist snuff ST products (hereafter referred to as portioned ST products) consist of moist snuff contained within pouches resembling small tea bags. Like loose ST products, portioned ST products are typically placed between the cheek and gum.

ST use topography, such as frequency of use, deposition time in the mouth, and the amount of product used per occasion, varies widely between ST users, and evidence suggests such changes in use topography may affect nicotine exposure.^8–10 Further, data from a survey study conducted in Sweden (n = 2,914) suggests loose snus users consume a greater amount of snus per day than portioned snus users (29–32 g vs. 11–12 g, respectively).¹¹ However, no published clinical studies to date have prospectively examined use behavior, abuse liability, and nicotine exposure as a function of ST product format among moist snuff users.

Product characteristics, such as total nicotine content, have also been found to affect nicotine absorption from ST products.¹² Further, some clinical evidence suggests free nicotine content may affect nicotine exposure from ST products.^13,14 Free nicotine (or unprotonated nicotine) content is determined by total nicotine content and product pH. Free nicotine is believed to be more readily absorbed through oral tissue than the protonated forms.^15,16 The free nicotine content of marketed ST products varies widely in the United States, ranging from 1% to 75% of total nicotine content¹⁷; therefore, the impact of the free nicotine content of ST products on abuse liability and use behavior warrants further investigation.

The current study evaluated the behavioral pharmacology of loose versus portioned ST use within a single study session among adult daily ST users. The primary aims of the current study were to evaluate differences in ST use topography between users of loose and portioned ST products and to compare nicotine pharmaco*kinetic (PK) parameters between users of loose versus portioned ST products. In addition, post hoc analyses examined possible associations between ST nicotine content (free nicotine and total nicotine) and nicotine exposure.

Methods

Participants

Battelle recruited prospective participants via local printed and online advertisem*nts in the Baltimore, Maryland, United States, area. Participants were compensated for participating in the study up to $300 (USD) for those completing all assessments. Prior to study recruitment, all procedures were approved by the Battelle and U.S. Food and Drug Administration institutional review boards. Participants were daily ST users who were current users of loose ST (n = 30) or portioned ST (n = 20). Inclusion criteria were (1) fluent in English, (2) 18 to 65 years of age, (3) daily ST use of a single brand and type of either loose or portioned moist ST for the past 6 months, (4) not seeking treatment for tobacco use, and (5) no clinically significant contraindications. Exclusion criteria were (1) use of any smoking cessation medications or nicotine replacement therapy within the past 60 days, (2) a clinically significant concomitant medical condition at screening, (3) evidence of any oral lesions of the lips, palate, tongue, or gums, (4) signs of obvious intoxication on test day, (5) participation in any other clinical trials involving a medication or tobacco product during past 6 months, and (6) declared intent to stop using ST in the next month.

Study Design and Measures

This was a single-center, open-label, two-parallel-arm study that compared use behavior, nicotine exposure, and other abuse liability outcomes between daily loose and portioned ST users. Participant visits took place at Battelle’s clinical pharmacology laboratory in Baltimore, Maryland, United States, between July 24, 2015 and August 26, 2016. All products used in the study were usual-brand ST purchased by the research participants. Following overnight abstinence from nicotine and tobacco products, each participant attended one laboratory session wherein they used their usual brand of ST (loose or portioned). During the first hour of the session, participants used a single “pinch” or portion of ST, and plasma nicotine concentrations were measured from blood samples collected before and 5, 10, 15, 30, 45, and 60 min after use. During the remaining 7 h, participants used ST ad libitum, and plasma nicotine concentrations were measured every 30 min until 180 min had elapsed since first use and then every hour until 8 h had elapsed since first use. PK parameters (C_max [peak plasma concentration], T_max [time to peak plasma concentration], and AUC [area under the curve]) were determined from the plasma nicotine concentrations. The measures of C_max and T_max were directly observed from the data, whereas AUC profiles were evaluated using the non-compartmental analysis module in the WinNonlin software program (Version 6.4, Pharsight Corporation, Sunnyvale, CA). Topography measurements of ST product use were recorded, including the time the product was used, the amount of product used (weight of loose product or number of pouches), the number of times it was used, and the length of time the product was kept in the mouth. Baseline nicotine dependence was assessed using a modified Hooked on Nicotine Checklist¹⁸ and modified fa*gerström Test for Nicotine Dependence.¹⁹

Product Characterization

Participants provided an unopened package of their usual brand of ST for chemical characterization (total and free nicotine content, pH). Chemical characterization analyses were conducted by Enthalpy Analytical (Richmond, VA). Product nicotine content was analyzed using Gas chromatography–mass spectrometry AM 100 methods. Samples were extracted with aqueous sodium hydroxide (2N) and methanol, and nicotine was quantified using an internal standard (quinoline or d4-nornicotine) and reported as µg/g. The aqueous pH of the products was tested from tobacco extracts prepared by grinding the product. Degassed water was added, and the samples were shaken. Free nicotine was estimated using the Henderson-Hasselbalch equation.²⁰ Finally, participant plasma samples were analyzed for nicotine at Virginia Commonwealth University School of Pharmacy using Liquid chromatography–mass spectrometry methods.

Statistical Analysis

The non-parametric Mann-Whitney test was used to compare outcomes between loose and portioned groups. Spearman’s rank correlations (r_s) were estimated to assess the strength of association between two outcomes, including associations between ST nicotine content (free nicotine and total nicotine), use topography, and nicotine exposure. Nonparametric tests were used due to the small sample size and lack of assumption about the distribution of the data. For all statistical tests, statistical significance was defined as p < .05.

Results

Participants averaged 34.1 years of age, were 74% white, 4% Hispanic/Latino, and 98% male. Of the sample, 34% had a high school diploma or Graduate Equivalency Degree (GED), 34% had some level of college education, and 14% of participants were fully employed. There were no significant demographic differences between the two ST format groups (see Supplementary Table 1).

Regarding baseline tobacco-use characteristics, modified Hooked on Nicotine Checklist (M = 7.3, SD = 2.5) and fa*gerström Test for Nicotine Dependence (M = 4.9, SD = 2.4) scores were not significantly different between the two groups. Participants reported first ST use on average at 21 (SD = 8.6) years of age and regular use by 24.2 (SD = 9.2) years of age. The average duration of regular use in the two groups was 8.2 (SD = 5.0) years. The number of uses per day averaged 8.6 (SD = 4.4) dips for the loose ST group and 7.4 (SD = 3.2) pouches for the portioned ST group. Among the loose ST group, the most popular ST brands were Grizzly (33%), Copenhagen (30%), and Skoal (23%). Among the portioned ST group, the most popular ST brands were Grizzly (60%), Camel (25%), and Skoal (15%). In both groups, 80% reported regular use of wintergreen or mint flavored ST products. Finally, 51% of participants indicated that they were current dual users of ST and combusted cigarettes (58.3% loose ST group, 42.1% portioned ST group), 43.2% indicated they were current users of cigars (38.1% loose ST group, 50.0% portioned ST group), and 17.1% indicated they were current e-cigarette users (13.6% loose ST group, 23.1% portioned ST group).

Data from two participants were removed from subsequent analyses as outliers. One participant was in the portioned ST group and used a product with 20.48 mg/g free nicotine (5.9 standard deviations above the mean), and the other participant was in the loose ST group and used a total amount of 74.7 g (5.8 standard deviations above the mean).

Table 1 shows the product characteristics of participants’ usual-brand ST products, including total nicotine content, pH, and free nicotine content. The pH of the ST products was within the range of pH levels observed in other ST products on the US market^21–23 and did not differ significantly between the portioned (M = 7.11, SD = 0.25) and loose (M = 7.18, SD = 0.37) ST groups (p > .05). Total nicotine content, and to a greater extent, free nicotine content, varied considerably across products. The range of total nicotine content for all products was 12.52 to 54.73 mg/g, and the range of free nicotine content for all products was 0.72 to 6.68 mg/g. Free nicotine content also varied considerably within the same brand. For example, the free nicotine content of Grizzly Long Cut Wintergreen ranged from 2.64 mg/g to 6.68 mg/g. On average, portioned ST products had significantly higher total nicotine concentration than loose ST products (M = 31.63 mg/g, SD = 12.53 vs. M = 20.54 mg/g, SD = 4.01; U = 131, p = .002). Free nicotine concentration did not significantly differ between the portioned (M = 3.42 mg/g, SD = 1.39) and loose (M = 2.79 mg/g, SD = 1.53) ST groups. These patterns were not observed across all loose and portioned products, such that some portioned ST products had similar or lower nicotine and free nicotine concentrations relative to some loose ST products.

Table 2 shows use topography outcomes measured during experimental sessions. Overall, participants in the loose ST group had significantly higher average amount per use during test day (M = 2.99 g, SD = 1.83 vs. M = 1.52 g, SD = 0.70; U = 144, p = .005; 95% confidence interval (CI) of the difference between loose and portioned measures = 0.31−2.05 g) and total amount used during the test day (M = 11.45 g, SD = 6.50 vs. M = 5.40 g, SD = 2.57; U = 129, p = .002; 95% CI of difference = 2.35−9.79 g). Frequency of use, as well as average and total deposition time over test day, did not significantly differ between the two groups.

Table 3 shows summary statistics for plasma nicotine PK parameters. First use nicotine C_max was significantly higher among the loose ST group than the portioned ST group (M = 33.4 ng/ml, SD = 18.0 vs. M = 19.0 ng/ml, SD = 13.0; U = 137.5, p = .003; 95% CI. of difference = 4.9−21.6 ng/ml), as was AUC_{0–1 h} (M = 1474.8 min*ng/ml, SD = 868.1 vs. M = 807.2 min*ng/ml, SD = 606.9; U = 136, p = .003; 95% CI of difference = 224−909 min*ng/ml). In addition, nicotine C_max during the ad libitum use period was significantly higher among the loose ST group than the portioned ST group (M = 56.3 ng/ml, SD = 25.0 vs. M = 30.8 ng/ml, SD = 16.4; U = 95, p < .00; 95% CI of difference = 11.9−32.9 ng/ml), as was AUC_{0–8 h} (M = 15827.9 min*ng/ml, SD = 8690.7 vs. M = 8155.3 min*ng/ml, SD = 5657.9; U = 112.5, p < .001; 95% CI of difference = 3000−10 300 min*ng/ml). No significant differences were observed between groups with respect to nicotine T_max.

The majority of product use behaviors were not significantly correlated with total or free nicotine content, with the exception of average amount per use of loose ST and total nicotine content (r_s = .385, p = .040), total amount used and free nicotine content (r_s = −0.381, p = .042 loose ST only), and average deposition time per use and free nicotine content (r_{s =} 0.382, p = .042 loose ST only). Notably, correlations were not estimated to examine relationships between average amount per use of portioned ST products and other variables because the amount used by portioned ST users was primarily determined by pouch size and showed limited variability across participants.

Due to the correlations observed between some measures of use topography and total or free nicotine content, partial Spearman’s rank correlations between plasma nicotine and total/free nicotine content were adjusted for amount used by participants. Table 4 shows correlations between total and free nicotine content and plasma nicotine PK parameters. There were no significant correlations between total nicotine content and plasma nicotine PK parameters. However, significant positive correlations were observed between free nicotine content and first use nicotine C_max for the loose ST group (r_s =.488, p = .011), but not the portioned ST group, and between free nicotine content and AUC_{0–1 h} for both ST groups (r_s =.448, p = .028, loose; r_s = .441, p = .024, portioned), even when adjusting for amount used. No significant correlations were observed between total or free nicotine content and first use nicotine T_max for either group.

Discussion

To our knowledge, the current study is the first to evaluate differences in use topography and nicotine PK among loose and portioned ST users who used their own brand of ST products while in a laboratory setting. The results show several differences in use topography between these two groups, including greater amounts of product per use, greater total amount used over the entire test day, and greater deposition time per use in loose ST users relative to portioned ST users. These findings extend findings of a previous study that showed greater self-reported amounts of product used by loose snus users relative to portioned snus users.¹¹

Further, these findings underscore potential differences in relative risks associated with using loose versus portioned ST products. Although the current study did not measure biomarkers of tobacco-specific nitrosamines or chemically characterize ST products for harmful or potentially harmful constituents other than nicotine, the greater amount of ST used by loose ST users may lead to greater exposure to harmful or potentially harmful constituents relative to portioned ST users. Indeed, loose ST users in the current study had significantly higher nicotine exposure relative to portioned ST users even though both total and free nicotine content were higher for the portioned ST products, replicating previous findings that differences in use topography are associated with differences in nicotine exposure.^8–10 These differences in use behavior and nicotine exposure also suggest loose ST products may have higher abuse liability than portioned ST products. However, despite these differences in use behavior and nicotine exposure, baseline nicotine dependence did not differ significantly between the loose and portioned ST users. Thus, at least in the context of the current study, nicotine dependence measures did not correspond with differences in actual nicotine self-administration, although the current study was not powered to detect differences in dependence measures.

Nicotine content, especially free nicotine, varied considerably across participant’s usual-brand ST products, replicating previously published reports on the nicotine content of ST products in the U.S. market.¹⁷ Further, free nicotine content varied considerably even within ST brands. Other studies have also shown considerable variability in free nicotine content within the same brand of ST products.²¹ However, the extent of such within-brand variability is unclear, as is whether such differences are due to differences in formulation, storage conditions, location of sale, or other factors. ST products analyzed in the current study were likely purchased in and around Baltimore, Maryland in 2015 and 2016; however, study participants could have purchased the products in other locations. Regardless of where the products were purchased, results from this study suggest that free nicotine content varies considerably within ST brands, and such variability may warrant further systematic investigation. Moreover, results of the current study show, regardless of ST brand or format, free nicotine content was positively associated with plasma nicotine PK measures, but total nicotine content was not, supporting previous findings that free nicotine content plays an important role in nicotine exposure from ST products.^13,14

The current investigation has several strengths worth noting. First, to our knowledge, this is the first study in which participants used their own brand of ST products in a closely monitored laboratory setting. As such, we captured aspects of more “naturalistic” use as participants used products they were already familiar with while measures of use topography were objectively assessed rather than dependent upon self-report as in previous studies.¹¹ Second, participants’ own brands of ST products were chemically characterized, and associations between product characteristics, use behavior, and nicotine exposure were explored.

Several study limitations are also worth noting. First, product formulations and characteristics such as free and total nicotine content were not prospectively isolated as independent variables; thus, these and other product characteristics (eg, flavor ingredients, cut of tobacco) varied between participants and may have influenced outcomes. Second, participants in the current study were not randomized to loose or portioned ST groups, and the relationships observed between ST content and study outcomes, including use topography and nicotine exposure, were correlational in nature. Future investigations may experimentally isolate some of these variables. Indeed, a randomized study recently isolated the effects of pH and found a strong relationship between the free nicotine content of ST products and abuse liability.²⁴ Third, due to the ad libitum phase of the study, which resulted in different times of use and amounts of tobacco used (eg, pinches or pouches), there was no “typical” concentration-time profile, and therefore, only non-adjusted PK parameters were reported. As such, user-specific modulators were not controlled for, particularly the body weight of the participant (which may have affected nicotine metabolism) and how factors such as length of time of ST use (eg, <1 year vs. several years) and dual-use factors (eg, dual-users vs. polytobacco users) affect use topography and nicotine exposure. Finally, the current study was made up of almost entirely White, male participants. Although this is the demographic that typically uses ST in the United States,^2,25 other demographics may be better represented in populations of ST users around the globe, and ST products produced in other countries may also differ from ST products manufactured in the United States^11,26; therefore, the generalizability of the current findings to other user populations and ST products may be topics of future investigations.

Study limitations notwithstanding, the current study was the first to demonstrate differences in use topography and nicotine exposure between loose and portioned ST users. Results suggest that loose ST users may use more ST products than portioned ST users. Results also showed that nicotine exposure from ST was more strongly associated with free nicotine content than total nicotine content, particularly among loose ST users. Additional research may be warranted to determine whether increased use of loose ST or exposure to free nicotine may lead to increased dependence or exposure to other ST constituents (eg, tobacco-specific nitrosamines). Although the current study found no relationship between ST format and baseline measures of dependence, investigating this relationship in a larger sample may be warranted.

Supplementary Material

A Contributorship Form detailing each author’s specific involvement with this content, as well as any supplementary data, are available online at https://academic.oup.com/ntr.

Funding

Research was supported by a contract awarded to Battelle by the Food and Drug Administration (Center for Tobacco Products) Contract HHSF223201310030I/HHSF22301002T.

Declaration of Interests

The authors have no conflicts of interest to disclose.

Disclaimer

The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Food and Drug Administration.

Data Availability Statement

The data underlying this article will be shared on reasonable request to the corresponding author.

References

Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco 2022.

Comments

0 Comments

I agree to the terms and conditions. You must accept the terms and conditions.

Email alerts

Citing articles via

More from Oxford Academic