Nicotine Population Pharmacokinetics in Healthy Adult Smokers: A Retrospective Analysis

Nicotine and Cardiovascular Health: When Poison is Addictive - a WHF Policy Brief

Nicotine is universally recognized as the primary addictive substance fuelling the continued use of tobacco products, which are responsible for over 8 million deaths annually. In recent years, the popularity of newer recreational nicotine products has surged drastically in many countries, raising health and safety concerns. For decades, the tobacco industry has promoted the myth that nicotine is as harmless as caffeine. Nonetheless, evidence shows that nicotine is far from innocuous, even on its own. In fact, numerous studies have demonstrated that nicotine can harm multiple organs, including the respiratory and cardiovascular systems. Tobacco and recreational nicotine products are commercialized in various types and forms, delivering varying levels of nicotine along with other toxic compounds. These products deliver nicotine in profiles that can initiate and perpetuate addiction, especially in young populations. Notably, some electronic nicotine delivery systems (ENDS) and heated tobacco products (HTP) can deliver concentrations of nicotine that are comparable to those of traditional cigarettes. Despite being regularly advertised as such, ENDS and HTP have demonstrated limited effectiveness as tobacco cessation aids in real-world settings. Furthermore, ENDS have also been associated with an increased risk of cardiovascular disease. In contrast, nicotine replacement therapies (NRT) are proven to be safe and effective medications for tobacco cessation. NRTs are designed to release nicotine in a slow and controlled manner, thereby minimizing the potential for abuse. Moreover, the long-term safety of NRTs has been extensively studied and documented. The vast majority of tobacco and nicotine products available in the market currently contain nicotine derived from tobacco leaves. However, advancements in the chemical synthesis of nicotine have introduced an economically viable alternative source. The tobacco industry has been exploiting synthetic nicotine to circumvent existing tobacco control laws and regulations. The emergence of newer tobacco and recreational nicotine products, along with synthetic nicotine, pose a tangible threat to established tobacco control policies. Nicotine regulations need to be responsive to address these evolving challenges. As such, governments should regulate all tobacco and non-medical nicotine products through a global, comprehensive, and consistent approach in order to safeguard tobacco control progress in past decades.

Cigarette Smoking as a Risk Factor for Hematoma Expansion in Primary Intracerebral Hemorrhage: Analysis From a Randomized Clinical Trial

Background Cigarette smoking is a well-known risk factor for ischemic and hemorrhagic stroke. We evaluated the impact of smoking status on hematoma expansion and clinical outcome in patients with primary intracerebral hemorrhage. Methods and Results This is a post hoc exploratory analysis of the ATACH (Antihypertensive Treatment at Acute Cerebral Hemorrhage)-2 trial. Patients with intracerebral hemorrhage were randomized into intensive blood pressure lowering (systolic blood pressure, <139 mm Hg) versus standard blood pressure lowering (systolic blood pressure, 140-179 mm Hg) in this study. We compared the demographic characteristics; hematoma size, location, and expansion rate; and clinical outcome based on subjects' smoking status. Of a total of 914 patients in the trial with known smoking status, 439 (48%) patients were ever smokers (264 current smokers and 175 former smokers). Current and former smokers were younger and more likely to be men. Baseline Glasgow Coma Scale score and initial hematoma size did not vary based on smoking status. Ever smokers had higher rates of thalamic hemorrhage (42% versus 34%) and intraventricular hemorrhage (29% versus 23%); this rate was highest among former smokers versus current smokers (49% versus 35%, respectively). Ever smokers had a higher rate of hematoma expansion in 24 hours (adjusted relative risk [RR] [95% CI], 1.46 [1.08-1.96]) compared with nonsmokers on multivariate analysis. There was no significant difference in the rate of death and disability at 90 days between the 2 groups (adjusted RR [95% CI], 1.18 [0.998-1.40]). Conclusions Our analysis demonstrates cigarette smoking as an independent predictor for hematoma expansion. There was no significant difference in death and disability based on smoking status.

Prolonged, physiologically relevant nicotine concentrations in the airways of smokers

Nicotine from cigarette smoke is a biologically active molecule that has pleiotropic effects in the airway, which could play a role in smoking-induced lung disease. However, whether nicotine and its metabolites reach sustained, physiologically relevant concentrations on airway surfaces of smokers is not well defined. To address these issues, concentrations of nicotine, cotinine, and hydroxycotinine were measured by mass spectrometry (MS) in supernatants of induced sputum obtained from participants in the subpopulations and intermediate outcome measures in COPD study (SPIROMICS), an ongoing observational study that included never smokers, former smokers, and current smokers with and without chronic obstructive pulmonary disease (COPD). A total of 980 sputum supernatants were analyzed from 77 healthy never smokers, 494 former smokers (233 with COPD), and 396 active smokers (151 with COPD). Sputum nicotine, cotinine, and hydroxycotinine concentrations corresponded to self-reported smoking status and were strongly correlated to urine measures. A cutoff of ∼8-10 ng/mL of sputum cotinine distinguished never smokers from active smokers. Accounting for sample dilution during processing, active smokers had airway nicotine concentrations in the 70-850 ng/mL (∼0.5-5 µM) range, and concentrations remained elevated even in current smokers who had not smoked within 24 h. This study demonstrates that airway nicotine and its metabolites are readily measured in sputum supernatants and can serve as biological markers of smoke exposure. In current smokers, nicotine is present at physiologically relevant concentrations for prolonged periods, supporting a contribution to cigarette-induced airway disease.

Evaluation of Ethnicity Effect on Intranasal Esketamine Pharmacokinetics by Population Pharmacokinetic Modeling Using Data From a Japanese Phase 2b Study

Esketamine is used for the treatment of treatment-resistant depression in many countries. A population pharmacokinetic (popPK) model of esketamine and its metabolite (noresketamine) has been previously developed, which included Asian race and Japanese ethnicity as covariates on their exposures. The present study aimed to update the popPK model by adding new data from a phase 2b study in Japanese patients and reassess intrinsic and extrinsic factors on esketamine and noresketamine exposures. The updated model identified the effects of body weight on the fraction of the esketamine dose absorbed in the nasal cavity and elimination rate constant of esketamine, and Asian race on the apparent clearance of noresketamine. The model predicted that an increase of 30 kg of body weight would decrease esketamine exposures by ≈20%. Noresketamine exposures would be affected by Asian race and body weight. However, those newly identified covariates were not considered to have clinically relevant impacts, and therefore dose adjustments were not necessary. In conclusion, the popPK model of esketamine and noresketamine was successfully updated and suggested that interindividual variability of esketamine exposures can be better explained by body weight, rather than by race/ethnicity. The new findings obtained in this study should be useful information for the further development of esketamine and for clinical practice in the future.

The pH of Smokeless Tobacco Determines Nicotine Buccal Absorption: Results of a Randomized Crossover Trial

Nicotine absorption rate influences tobacco products' addictiveness. For smokeless tobacco, nicotine buccal absorption is associated with its free-base form; the pH of smokeless tobacco defines the proportion of free-base (i.e., unprotonated) vs. protonated nicotine. This was the first study to compare nicotine pharmacokinetics (PK) and pharmacodynamics (PD) after the use of commercial smokeless tobacco products that were experimentally manipulated to differ only in pH and percent free-base nicotine. Moist snuff users (N = 40) completed four crossover visits and used a single 2 g portion of Copenhagen Original Long Cut amended to 4 pH levels: 5.0, 7.7, 8.2, and 8.6 (free-base nicotine 0.1, 32, 60, and 79%) for 30 minutes. Nicotine PK and PD were assessed for 4 hours post-use. Nicotine PK substantially depends on its free-base proportion, with more than 4-fold increases in mean plasma nicotine maximum concentration and area under the curve over 240 minutes (3.9 to 16.7 ng/mL; 385 to 1810 ng min/mL, respectively, both P < 0.001) from pH 5.0 to 8.6. The autonomic cardiovascular effects of smokeless tobacco use reflected percent free-base nicotine, with small (albeit significant) systematic increases in heart rate and blood pressure associated with free-base nicotine. Smokeless tobacco product pH and percent free-base nicotine play a major role in the rate and extent of nicotine absorption, determining product PD effects and abuse potential. Research and regulation of smokeless tobacco products should consider both total nicotine content and product pH. Further research may address the impact of modifying pH on the addictiveness of smokeless tobacco and associated use behaviors.

Effectiveness of Non-Nicotinic E-Cigarettes to Reduce Cue- and Abstinence-Induced Cigarette Craving in Non-Treatment Seeking Daily Dependent Smokers

RATIONALE

Electronic cigarettes (e-cigarettes) are potential tools for smoking cessation because they deliver nicotine and simulate smoking behaviors. The contribution of sensorimotor versus pharmacological substitution is unknown.

OBJECTIVES

To evaluate whether non-nicotinic e-cigarettes, used alone or with nicotine lozenges, can attenuate cigarette craving following visual cue presentation or acute (3 h post ad-lib use) abstinence in dependent daily smokers.

METHODS

Following overnight (12 hours) abstinence, 41 daily smokers were exposed to 4 experimental conditions on separate days: (i) tobacco cigarettes (CIG); (ii) non-nicotinic e-cigarettes with placebo lozenges (EPL); (iii) non-nicotinic e-cigarettes with 4 mg nicotine lozenge (ENL); and (iv) 4 mg nicotine lozenge (NL). Cigarette craving was assessed following presentation of neutral and smoking cues at various time points using the Brief Questionnaire of Smoking Urges (QSU-B) and visual analog scales (VAS).

RESULTS

All experimental conditions significantly reduced participants' baseline overnight abstinence cigarette craving. ENLs and NLs attenuated smoking-cue-induced cravings to a greater extent than CIGs, where cravings were significantly higher with CIGs compared to ENLs [mean difference (MD) ± standard error (SE) in QSU-B = 3.2 ± 0.84, P = 0.002; VAS = 12.7 ± 2.7, P < 0.0005] and NLs [MD ± SE in QSU-B = 2.7 ± 0.92, P = 0.031; VAS = 8.1 ± 2.3, P = 0.005]. Craving responses to cues after 3 h were higher after smoking CIGs compared to ENLs [MD ± SE in QSU-B = 3.9 ± 1.4, P = 0.047; VAS = 14.1 ± 3.6, P = 0.002] and NLs [MD ± SE in QSU-B = 3.2 ± 1.1, P = 0.046; VAS = 9.7 ± 3.1, P = 0.017].

CONCLUSIONS

Behavioral simulation of smoking with or without nicotine reduces nicotine craving. Compared to cigarettes, ENL with NL or NL alone attenuates cigarette craving over time. Future clinical trials should evaluate the combination of ENL and NL as a method for smoking reduction or cessation.

TRIAL REGISTRATION

NCT02108626.

Effects of smoking on delayed neuropsychiatric sequelae in acute carbon monoxide poisoning: A prospective observational study

Smoking is a well-known risk factor for cardio-cerebrovascular disease. However, several studies have reported the "smoker's paradox" whereby smokers have a better prognosis for cardio-cerebrovascular diseases. Similar to cardio-cerebrovascular diseases, hypoxia is one of the major mechanisms of injury in carbon monoxide (CO) poisoning. This study investigated the association between smoking and delayed neuropsychiatric sequelae (DNS) in acute CO poisoning.This study involved patients with CO poisoning treated at a university hospital in Bucheon, Korea between September 2017 and March 2020. The exclusion criteria were age <18 years, discharge against medical advice, loss to follow-up, persistent neurological symptoms at discharge, transfer from another hospital 24 hours after exposure, and transfer from another hospital after hyperbaric oxygen therapy. Logistic regression analysis was performed to find factors associated with DNS.Two hundred sixty three patients visited the hospital due to CO poisoning and of these, 54 were excluded. DNS was evaluated up to 3 months after discharge, and until this time, DNS occurred in 35 (16.8%) patients. And the incidence rate of DNS was lower in smokers than non-smokers (15, 12% vs 20, 23.8%, P = .040). Multivariable logistic regression analysis revealed that CO exposure time (odds ratio [OR] 1.003; confidence interval [CI] 1.001-1.005; P = .003), the Glasgow coma scale (GCS) (OR 0.862; CI 0.778-0.956; P = .005), and pack-years (OR 0.947; CI 0.903-0.993; P = .023) were statistically significant for DNS development.These results indicate that more pack-years smoked were associated with reduced risk of the development of DNS in acute CO poisoning, and that CO exposure time and GCS is a predictive factor for DNS occurrence.

Nicotine Population Pharmacokinetics in Healthy Smokers After Intravenous, Oral, Buccal and Transdermal Administration

Background

In 4 decades, numerous nicotine replacement therapy products have been developed. Population pharmacokinetic models can support exposure–response modeling and inform nicotine replacement therapy product development, but only limited model-based cross-study population pharmacokinetic analyses for nicotine replacement therapy products have been published.

Objectives

The aim of this retrospective analysis was to assess the population pharmacokinetics of nicotine across intravenous, oral, transdermal and oromucosal (mouth spray, chewing gum, lozenge and inhaler) routes and formulations in healthy smoking subjects.

Methods

Data on 930 unique subjects (46,016 observations) from 29 single- and repeated-dose studies with multiple formulations across intravenous, oral, transdermal and oromucosal routes of administration were included. Data from intravenous and extravascular routes of administration were modelled separately for run efficiency reasons. For developing extravascular models, clearance and disposition parameters and their inter-individual variabilities were fixed to the estimates for intravenously delivered nicotine. Detectable pre-dose nicotine concentrations were modelled as a hypothetical nicotine bolus into the central compartment at the start of wash-out. Modelling repeated-dose oral and buccal administrations required a time-dependent increase in clearance or decrease in bioavailability to describe the data adequately.

Results

Disposition of intravenous nicotine was best described by a three-compartment model with initial and terminal half-lives of 7 min and 4.5 h, respectively, and the absorption of single oral doses was best described with a first-order absorption rate constant of 1.55 h⁻¹. The data of buccal formulations were modelled with parallel oromucosal absorption and gastrointestinal absorption of a part of the dose that is swallowed. For transdermal nicotine, parallel zero- and first-order release from the patch and a transit-compartment absorption model best described the data. Key pharmacokinetic parameters were reliably estimated, with typical values for clearance (67 L/h for a 70-kg subject), volume of distribution (4.3 L/kg), oral bioavailability (40%) and transdermal bioavailability (76%) within expected ranges. The estimated fraction of the dose swallowed for buccal formulations ranged from 55% (gum) to 69% (lozenge).

Conclusions

Robust population pharmacokinetic models were developed for five nicotine replacement therapy product types and for intravenous and oral nicotine. These population pharmacokinetic models are used in exposure–response analyses and simulation-based nicotine replacement therapy product design.

Electronic supplementary material

The online version of this article (10.1007/s40262-020-00960-5) contains supplementary material, which is available to authorized users.

Low acetylcholine during early sleep is important for motor memory consolidation

The synaptic homeostasis theory of sleep proposes that low neurotransmitter activity in sleep optimizes memory consolidation. We tested this theory by asking whether increasing acetylcholine levels during early sleep would weaken motor memory consolidation. We trained separate groups of adult mice on the rotarod walking task and the single pellet reaching task, and after training, administered physostigmine, an acetylcholinesterase inhibitor, to increase cholinergic tone in subsequent sleep. Post-sleep testing showed that physostigmine impaired motor skill acquisition of both tasks. Home-cage video monitoring and electrophysiology revealed that physostigmine disrupted sleep structure, delayed non-rapid-eye-movement sleep onset, and reduced slow-wave power in the hippocampus and cortex. Additional experiments showed that: (1) the impaired performance associated with physostigmine was not due to its effects on sleep structure, as 1 h of sleep deprivation after training did not impair rotarod performance, (2) a reduction in cholinergic tone by inactivation of cholinergic neurons during early sleep did not affect rotarod performance, and (3) stimulating or blocking muscarinic and nicotinic acetylcholine receptors did not impair rotarod performance. Taken together, the experiments suggest that the increased slow wave activity and inactivation of both muscarinic and nicotinic receptors during early sleep due to reduced acetylcholine contribute to motor memory consolidation.

Assessing the lung cancer risk reduction potential of candidate modified risk tobacco products

Smoking is the major cause of lung cancer. While the risk of lung cancer increases with the number of cigarettes smoked and the duration of smoking, it also decreases upon smoking cessation. The development of candidate modified risk tobacco products (cMRTP) is aimed at providing smokers who will not quit with alternatives to cigarettes that present less risk of harm and smoking-related disease. It is necessary to assess the risk reduction potential of cMRTPs, including their potential to reduce the risk of lung cancer. Assessing the lung cancer risk reduction potential of cMRTPs is hampered by (i) the absence of clinical risk markers that are predictive of future lung cancer development, (ii) the latency of lung cancer manifestation (decades of smoking), and (iii) the slow reduction in excess risk upon cessation and a fortiori upon switching to a cMRTP. It is, therefore, likely that only long-term epidemiology will provide definitive answers to this question and allow to first verify that a cMRTP reduces the risk of lung cancer and if it does, to quantify the reduction in excess lung cancer risk associated with a cMRTP. For this to be possible, the cMRTP would need to be available in the market and used exclusively by a large portion of current smokers. Here, we propose that a mechanism-based approach represents a solid alternative to show in a pre-market setting that switching to a cMRTP is likely to significantly reduce the risk of lung cancer. This approach is based on the causal chain of events that leads from smoking to disease and leverages both non-clinical and clinical studies as well as the principles of systems toxicology. We also discuss several important challenges inherent to the assessment of cMRTPs as well as key aspects regarding product use behavior.

Effect of Cigarette Smoking on Functional Outcomes in Patients with Spontaneous Intracerebral Hemorrhage

BACKGROUND

Nicotine may have neuroprotective effects on the injured brain through modulation of the cholinergic anti-inflammatory pathway.

AIMS

This study aimed to evaluate the relationship between cigarette smoking and outcomes in patients with spontaneous intracerebral hemorrhage (ICH).

METHODS

This was a retrospective review of consecutive ICH patients enrolled in the ICH Outcomes Project from 2009 to 2017. Patients with age ≥18 years and baseline modified Rankin Scale (mRS) score 0-2 were included. Smoking patterns were categorized as recent smoker (≤30 days prior to ICH) and not recent smoker (>30 days prior to ICH). Not recent smokers were further categorized into former smokers and nonsmokers. The primary outcome was good outcome (90-day mRS ≤ 2). Secondary outcomes were excellent outcome (90-day mRS 0-1), 90-day Barthel Index, and in-hospital and 90-day mortality.

RESULTS

The study cohort comprised 545 patients, including 60 recent smokers and 485 not recent smokers. Recent smokers had higher rates of good (35% versus 23%; odds ratio [OR] = 1.787, P = .047) and excellent (25% versus 13%; OR = 2.220, P = .015) outcomes compared to not recent smokers. These differences were not significant after baseline adjustments. Recent smokers had higher rates of good (36% versus 24%; OR = 1.732, P = .063) and excellent (25% versus 13%; OR = 2.203, P = .018) outcomes compared to nonsmokers. These differences were not significant after baseline adjustments. A 90-day Barthel Index, in-hospital, and 90-day mortality were comparable between recent and not recent smokers, recent and nonsmokers, and former and nonsmokers.

CONCLUSIONS

Despite potential neuroprotective effects of nicotine found in cigarettes, these may be outweighed by the detrimental effects of cigarette smoking on health outcomes.

Nicotine pharmacokinetic profiles of the Tobacco Heating System 2.2, cigarettes and nicotine gum in Japanese smokers

Two open-label randomized cross-over studies in Japanese smokers investigated the single-use nicotine pharmacokinetic profile of the Tobacco Heating System (THS) 2.2, cigarettes (CC) and nicotine replacement therapy (Gum). In each study, one on the regular and one on the menthol variants of the THS and CC, both using Gum as reference, 62 subjects were randomized to four sequences: Sequence 1: THS - CC (n = 22); Sequence 2: CC - THS (n = 22); Sequence 3: THS - Gum (n = 9); Sequence 4: Gum - THS (n = 9). Plasma nicotine concentrations were measured in 16 blood samples collected over 24 h after single use. Maximal nicotine concentration (Cmax) and area under the curve from start of product use to time of last quantifiable concentration (AUC0-last) were similar between THS and CC in both studies, with ratios varying from 88 to 104% for Cmax and from 96 to 98% for AUC0-last. Urge-to-smoke total scores were comparable between THS and CC. The THS nicotine pharmacokinetic profile was close to CC, with similar levels of urge-to-smoke. This suggests that THS can satisfy smokers and be a viable alternative to cigarettes for adult smokers who want to continue using tobacco.