Disposition kinetics and effects of intravenous nicotine

Non-conventional toxin WTX and its disulfide-fixed synthetic fragments: Interaction with nicotinic acetylcholine receptors and reduction of blood pressure

Non-conventional snake venom toxins, such as WTX from the cobra Naja kaouthia, are three-finger proteins containing a fifth disulfide bond in the N-terminal polypeptide loop I and inhibiting α7 and muscle-type nicotinic acetylcholine receptors (nAChRs). Because the central polypeptide loop II of non-conventional toxins plays an important role in their biological activity, we synthesized several WTX loop II fragments with two cysteine residues added at the N- and C-termini and oxidized to form a disulfide bond. The inhibition by peptides of several nAChRs subtypes was investigated using different methods and the effects of peptides on the rat arterial pressure and heart rate were analyzed. The synthetic fragments inhibited α7 and muscle-type nAChRs more potently than WTX. We showed for the first time that WTX and its fragments inhibited α9α10 as well as neuronal α3β2 and α4β2 nAChRs, again the synthetic fragments being more potent than WTX. The loop II fragments reduced blood pressure more potently than WTX in normotensive, awake rats. In connection with this, the WTX cardiovascular effects were analyzed and it was found that toxin very weakly affected parameters of papillary muscle contractions with no influence on aortic ring contractility. The observed effects were not so significant to explain the decrease in BP, the hemodynamic effects of WTX appearing not to result from direct influence on the myocardium and blood vessels. The synthetic fragments of the N- and C-terminal loops I and III were inactive in all tests. Thus, both in inhibition of all analyzed nAChR subtypes and in reduction of blood pressure, fragments of the central loop II were more active than WTX. This appears to be a first indication for three-finger proteins that the fragments of the central loop II are more active than the native toxin.

Effects of Device Settings and E-Liquid Characteristics on Mouth-Throat Losses of Nicotine Delivered with Electronic Nicotine Delivery Systems (ENDS)

Currently it is not fully understood how the device settings and electronic liquid (e-liquid) composition, including their form of nicotine content, impact mouth and throat losses, and potentially lead to the variations in total nicotine delivery to the human lungs. An in situ size assessment method was developed for real-time measurements at the mouthpiece and outlet of a biorelevant mouth-throat to account for the dynamic nature of the aerosol. The aerosol size, temperature, and delivery through the mouth-throat replica and the exhaled aerosol between the puff intervals were measured at different wattages using various e-liquid compositions. The effects of body temperature and humidity on aerosol size and nicotine delivery were also explored to evaluate the importance of considering realistic in vivo conditions in in vitro measurements. Notably, in vitro tests with body temperature and humidity in mouth-throat model vs room conditions, resulted in larger aerosol size at the end of the throat (Dv50=5.83±0.33 μm vs 3.05±0.15 μm), significantly higher thoracic nicotine delivery (>90% vs 50-85%) potentially due to the lower exhaled amount (<10% vs 15-50%). Besides, higher VG/PG ratios resulted in significantly lower exhaled amount and higher mouth-throat nicotine deposition. One of the main outcomes of the study was finding significantly lower exhaled amount and higher thoracic nicotine delivery with nicotine salt form vs free-base. Considering body temperature and humidity also showed significant enhancement in nicotine delivery, so it is essential to account for biorelevant experimental conditions in benchtop testing.

Assessment of nicotine delivery and uptake in users of various tobacco/nicotine products

Today various tobacco and nicotine products are available, many of them can be regarded as potentially risk-reduced products when compared to the most frequently used product, combustible cigarettes (CCs). A commonality of these products is that they deliver nicotine, although in quite different amounts and uptake routes, the most common of which are inhalation through the lung and absorption through the oral mucosa. Product-specific nicotine delivery as well as the subject-related use patterns are important factors which determine the pharmacokinetics and achieved internal dose levels of the alkaloid. The latter two parameters are highly relevant for the long-term product loyalty and, consequently, for the implicated health risks, since the risk-reduced products will replace CCs in the long-term only when users will experience a similar level of satisfaction. We measured nicotine and its major metabolites in plasma, saliva and urine samples collected in a controlled clinical study with habitual users (10 per group) of CCs, electronic cigarettes (ECs), heated tobacco products (HTP), oral tobacco (OT), and nicotine replacement therapy (NRT). Non-users (NU) of any tobacco/nicotine products served as (negative) control group. Moderate to strong correlations were observed between the daily consumption and the urinary nicotine equivalents (comprising nicotine and its 10 major metabolites, Nic + 10) or plasma and saliva cotinine concentrations. The average daily nicotine dose as measured by the urinary excretion of Nic + 10 (reflecting approximately 95 % of the absorbed nicotine) amounted to 17 and 22 mg/24 h for smokers (CC) and OT users, respectively, while it was in the range of 6-12 mg/24 h for users of ECs, HTP and NRT products, with high inter-individual variations in each user group. The individual daily nicotine intake, which was calculated by applying product-specific models, showed none to good agreement with the corresponding internal nicotine dose measured by Nic + 10 excretion. Possible reasons for the observed deviations between calculated and objectively measured nicotine doses are discussed.

Adverse effects of cigarette and noncigarette smoke exposure on the autonomic nervous system: mechanisms and implications for cardiovascular risk

This review summarizes the detrimental effects of cigarette and noncigarette emission exposure on autonomic function, with particular emphasis on the mechanisms of acute and chronic modulation of the sympathetic nervous system. We propose that the nicotine and fine particulate matter in tobacco smoke lead to increased sympathetic nerve activity, which becomes persistent via a positive feedback loop between sympathetic nerve activity and reactive oxidative species. Furthermore, we propose that baroreflex suppression of sympathetic activation is attenuated in habitual smokers; that is, the baroreflex plays a permissive role, allowing sympathoexcitation to occur without restraint in the setting of increased pressor response. This model is also applicable to other nontobacco cigarette emission exposures (e.g., marijuana, waterpipes [hookahs], electronic cigarettes, and even air pollution). Fortunately, emerging data suggest that baroreflex sensitivity and autonomic function may be restored after smoking cessation, providing further evidence in support of the health benefits of smoking cessation.

Nicotine poisoning due to intravenous injection of cigarette soakage

A 27-year-old female nurse intravenously injected 5 mL of cigarette soakage solution that contained approximately 5.7 mg nicotine, in a suicidal attempt. Clinical manifestations consisted of nausea, palpitation, abdominal pain, repeated vomiting, and diarrhea. She remained fully conscious during this episode. About 7 hours later, she visited emergency department on foot and received fluid infusion for dehydration. She fully recovered at night of the day. This is the first documented report of acute nicotine poisoning due to intravenous injection of cigarette soakage in humans. Signs and symptoms appeared immediately after the injection, but this case seemed to be relatively mild in terms of clinical manifestation. The elimination half-life of nicotine seems to be short, that is, less than 1 hour. Therefore, if initial treatment is appropriate and the patient can survive acute phase of nicotine poisoning, prognosis is good.

Nicotinic plant poisoning

INTRODUCTION

A wide range of plants contain nicotinic and nicotinic-like alkaloids. Of this diverse group, those that have been reported to cause human poisoning appear to have similar mechanisms of toxicity and presenting patients therefore have comparable toxidromes. This review describes the taxonomy and principal alkaloids of plants that contain nicotinic and nicotinic-like alkaloids, with particular focus on those that are toxic to humans. The toxicokinetics and mechanisms of toxicity of these alkaloids are reviewed and the clinical features and management of poisoning due to these plants are described.

METHODS

This review was compiled by systematically searching OVID MEDLINE and ISI Web of Science. This identified 9,456 papers, excluding duplicates, all of which were screened. Reviewed plants and their principal alkaloids. Plants containing nicotine and nicotine-like alkaloids that have been reported to be poisonous to humans include Conium maculatum, Nicotiana glauca and Nicotiana tabacum, Laburnum anagyroides, and Caulophyllum thalictroides. They contain the toxic alkaloids nicotine, anabasine, cytisine, n-methylcytisine, coniine, n-methylconiine, and gamma-coniceine.

MECHANISMS OF TOXICITY

These alkaloids act agonistically at nicotinic-type acetylcholine (cholinergic) receptors (nAChRs). The nicotinic-type acetylcholine receptor can vary both in its subunit composition and in its distribution within the body (the central and autonomic nervous systems, the neuromuscular junctions, and the adrenal medulla). Agonistic interaction at these variable sites may explain why the alkaloids have diverse effects depending on the administered dose and duration of exposure.

TOXICOKINETICS

Nicotine and nicotine-like alkaloids are absorbed readily across all routes of exposure and are rapidly and widely distributed, readily traversing the blood-brain barrier and the placenta, and are freely distributed in breast milk. Metabolism occurs predominantly in the liver followed by rapid renal elimination.

CLINICAL FEATURES

Following acute exposure, symptoms typically follow a biphasic pattern. The early phase consists of nicotinic cholinergic stimulation resulting in symptoms such as abdominal pain, hypertension, tachycardia, and tremors. The second inhibitory phase is delayed and often heralded by hypotension, bradycardia, and dyspnea, finally leading to coma and respiratory failure.

MANAGEMENT

Supportive care is the mainstay of management with primary emphasis on cardiovascular and respiratory support to ensure recovery.

CONCLUSIONS

Exposure to plants containing nicotine and nicotine-like alkaloids can lead to severe poisoning but, with prompt supportive care, patients should make a full recovery.

Cigarette smoking as a cause of delay in conception

Epidemiological studies relating cigarette smoking to the ability to conceive and maintain a pregnancy provide information on the clinical significance of smoking on reproductive health. Cigarette smoking by females has significantly increased in the decades after World War II, and now has an average initiation at ages 18–20 years. Maternal smoking is a hazard to the general health, the reproductive health and the life of both mother and child. Gestational smoking renders the fetus a passive smoker. This can result in fetal and neonatal death and in reduced fecundity of adult daughters.

Determination of hair nicotine by gas chromatography-mass spectrometry

Hair nicotine is a known biomarker for monitoring long-term environmental tobacco smoke (ETS) exposure and smoking status. In general, hair nicotine assay involves alkaline digestion, extraction and instrumental analysis. The gas chromatography-mass spectrometry (GC-MS) assay currently developed has shown to be of high throughput with average approximately 100 hair samples being extracted and analyzed per day. This was achieved through simplified extraction procedure and shortened GC analysis time. The extraction was improved by using small volume (0.4 mL) of organic solvent that does not require further evaporation and salting steps prior to GC-MS analysis. Furthermore, the amount of hair utilized in the extraction was very little (5 mg) while the sensitivity and selectivity of the assay is equal, if not better than other established methods. The linearity of the assay (r(2)>0.995), limit of quantitation (0.04 ng/mg hair), within- and between-assays accuracies and precisions (<11.4%) and mean recovery (92.6%) were within the acceptable range.

Behavioural studies in humans: anxiety, stress and smoking

Numerous observers have reported that smokers smoke more under stressful conditions. The most frequent explanation is that nicotine reduces anxiety, an intervening variable identified as a negative reinforcer for smoking behaviour. The conditions under which anxiety reduction occurs in response to smoking, however, have not been well defined, nor are underlying mechanisms well understood. There are several possible explanations, including Schachter's theory based on stress-induced changes in urinary pH and the hypothesis of endogenous opioid involvement. The work of Collins and his associates in animals has shown that genetic variations in corticosteroid responsiveness to nicotine are associated with differences in sensitivity to nicotine. Research in our laboratory has extended to humans Collins' findings that sensitivity to nicotine is inversely related to corticosteroid activity. We also found that the combination of a psychological stressor and smoking produced additive effects on cortisol release in humans. These findings suggest a novel way of explaining the interaction between smoking and stress, in that increased nicotine intake in the context of stress may in part reflect behavioural compensation for diminished sensitivity to nicotine when corticosteroid activity is enhanced by the stressor.

Pharmacokinetic considerations in understanding nicotine dependence

The pharmacokinetic and pharmacodynamic characteristics of a drug are important determinants of whether users become dependent on it and of the temporal patterns of drug use. Characteristics of cigarette smoking, which produces a high degree of dependence, and the use of nicotine gum, which has a relatively low risk of dependence, are compared. Nicotine from tobacco smoke is rapidly absorbed and transferred into the brain. This results in high brain concentrations and intensive psychological effects, with relatively little development of tolerance. The smoker may titrate the level of drug and associated psychological effects of nicotine. Thus, smoking provides a nearly optimal situation for behavioural reinforcement. Chewing nicotine gum results in slow absorption of nicotine, leading to lower levels of nicotine in the brain and substantial time for development of tolerance. Thus, the intensity of effect is less and the onset of effect is delayed from the onset of dosing, providing less opportunity for behavioural reinforcement. Pharmacokinetic and pharmacodynamic modelling techniques have been applied to these processes and used to assess the implications for understanding the daily smoking cycle.

Interaction between nicotine and MPTP/MPP+ in rat brain endothelial cells

To examine the interaction between nicotine and MPTP/MPP+ in the blood-brain barrier, cellular uptake of MPTP and MPP+ was studied in the presence of nicotine and several compounds, including MPTP/MPP+ analogs and a specific inhibitor of organic cation transporter (OCT) in an adult rat brain microvascular endothelial cell line (ARBEC). The kinetic properties of the uptake of MPTP, MPP+, and nicotine were also examined. In addition, a microdialysis study was performed to evaluate the in vivo effect of nicotine (i.p.) on extracellular levels of MPTP and MPP+ in the brain after intravenous administration of MPTP. The results showed that uptake of MPTP, MPP+, and nicotine was partly mediated by a carrier system that was sensitive to decynium22, a specific OCT inhibitor. RT-PCR showed the presence of OCT1 mRNA in ARBEC. Capacity for uptake of MPTP and nicotine was much higher than that for MPP+ (Km and Vm values of 10.94+/-1.44 microM and 0.049+/-0.007 pmol/mg s, respectively, for MPP+, compared to values of 35.75+/-0.85 microM and 40.95+/-3.56 pmol/mg s for MPTP and 25.29+/-6.44 microM and 51.15+/-14.18 pmol/mg s for nicotine). In addition, nicotine competitively inhibited the uptake of both MPTP and MPP+, with inhibition constants (Ki) of 328 microM and 210 microM, respectively. In vivo microdialysis results showed that nicotine significantly reduced brain extracellular levels of MPTP in the first 30 min (507.4+/-8.5 ng/ml vs. 637.9+/-30.8 ng/ml with and without nicotine pre-treatment, respectively), but did not have significant effect on those of MPP+. In conclusion, nicotine can inhibit in vitro cellular uptake and in vivo transfer of MPTP across the blood-brain barrier, which can be mediated by multiple pathways including OCT1.

Application of nicotine enantiomers, derivatives and analogues in therapy of neurodegenerative disorders

This review gives a brief overview over the major aspects of application of the nicotine alkaloid and its close derivatives in the therapy of some neurodegenerative disorders and diseases (e.g. Alzheimer's disease, Parkinson's disease, Tourette's syndrome, schizophrenia etc.). The issues concerning methods of nicotine analysis and isolation, and some molecular aspects of nicotine pharmacology are included. The natural and synthetic analogues of nicotine that are considered for medical practice are also mentioned. The molecular properties of two naturally occurring nicotine enantiomers are compared--the less-common but less-toxic (R)-nicotine is suggested as a natural compound that may find its place in pharmaceutical practice.

In vivo human buccal permeability of nicotine

The aim was to examine the in vivo buccal pH-dependent permeability of nicotine in humans and furthermore compare the in vivo permeability of nicotine to previous in vitro permeability data. The buccal permeability of nicotine was examined in a three-way cross-over study in eight healthy non-smokers using a buccal perfusion cell. The disappearance of nicotine from perfusion solutions with pH 6.0, 7.4, and 8.1 was studied for 3h. The apparent permeability of nicotine (P(app)) was determined at each pH value. Parotid saliva was collected in an attempt to assess systemic levels of nicotine. The disappearance rate of nicotine increased significantly as the pH increased, which resulted in P(app) values of 0.57+/-0.55 x 10(-4), 2.10+/-0.23 x 10(-4), and 3.96+/-0.54 x 10(-4)cms(-1) (mean+/-S.D.) at pH 6.0, 7.4, and 8.1, respectively. A linear relationship (R(2)=0.993) was obtained between the P(app) values and non-ionised nicotine, which indicates that the nicotine transfer occurred by means of passive diffusion. P(app) values of 0.60 x 10(-4) and 6.18 x 10(-4)cms(-1) were obtained for the mono-protonated and non-ionised species of nicotine, respectively. The analysis of the parotid saliva samples indicated that these samples might be useful in the assessment of systemic absorption of nicotine. Previous buccal in vitro models underestimated the in vivo human permeability of nicotine. However, the in vitro models were capable of predicting the effect of pH on the nicotine permeability.

Involvement of specific transport system of renal basolateral membranes in distribution of nicotine in rats

We measured the nicotine concentrations in tissues after a bolus i.v. administration of [(3)H]nicotine to rats to characterize the distribution profile of nicotine. The kidney showed the greatest distribution of nicotine compared to other tissues including liver, lung, heart, brain, and intestine. We also performed an HPLC assay for the determination of nicotine and its major metabolite, cotinine, and found that cotinine was negligible in the distribution of almost all tissues, except for the kidney and lung. In the kidney, cotinine was detected at a lower level than nicotine, while cotinine tended to be distributed in the lung compared to nicotine. [(3)H]Nicotine was accumulated in renal slices in a concentration dependent fashion, suggesting that the nicotine uptake in the renal tubules could be mediated by a specific transport system. Unlabeled nicotine, cotinine, and quinidine showed potent inhibitory effects on [(3)H]nicotine uptake by renal slices. In contrast, tetraethylammonium (TEA), cimetidine, and N(1)-methylnicotinamide (NMN), which were substrates of renal organic cation transporters, had no effects on the uptake. These findings suggested that a specific transporter was involved in nicotine transport at the basolateral membranes of rat renal tubules, which could mediate the high accumulation of nicotine from blood into the kidney.

Human variability for metabolic pathways with limited data (CYP2A6, CYP2C9, CYP2E1, ADH, esterases, glycine and sulphate conjugation)

Human variability in the kinetics of a number of phase I (CYP2A6, CYP2C9, CYP2E1, alcohol dehydrogenase and hydrolysis) and phase II enzymes (glycine and sulphate conjugation) was analysed using probe substrates metabolised extensively (>60%) by these routes. Published pharmacokinetic studies (after oral and intravenous dosing) in healthy adults and available data on subgroups of the population (effects of ethnicity, age and disease) were abstracted using parameters relating primarily to chronic exposure [metabolic and total clearances, area under the plasma concentration time-curve (AUC)] and acute exposure (C(max)). Interindividual differences in kinetics for all these pathways were low in healthy adults ranging from 21 to 34%. Pathway-related uncertainty factors to cover the 95th, 97.5th and 99th centiles of healthy adults were derived for each metabolic route and were all below the 3.16 kinetic default uncertainty factor in healthy adults, with the possible exception of CYP2C9*3/*3 poor metabolisers (based on a very limited number of subjects). Previous analyses of other pathways have shown that neonates represent the most susceptible subgroup and this was true also for glycine conjugation for which an uncertainty factor of 29 would be required to cover 99% of this subgroup. Neonatal data were not available for any other pathway analysed.

Relationship between environmental tobacco smoke and urinary cotinine levels in passive smokers at their residence

Studies of the health effects of environmental tobacco smoke (ETS) using measured air concentrations are subject to bias. Cotinine, a nicotine metabolite detected in urine, has been recommended as a quantitative measure of nicotine intake and thus as a marker for ETS exposure in humans. The aim of this study was to correlate home indoor ETS levels with passive smokers' urinary cotinine levels. The urinary cotinine concentrations of 57 non-smoking women who spend >19 h a day at home and the nicotine levels in their living room air were measured over a period of 24 h. Nicotine and urinary cotinine levels were analyzed using GC/MS and HPLC/UV, respectively. In addition, information was collected regarding the smoking habits of the subjects' families. A significant correlation was found between the nicotine levels in indoor air and the urinary cotinine to creatinine ratio of the passive smokers. The smoking habits of the subjects' family members were also correlated to the urinary cotinine levels of the passive smokers.

Influence of arterial vs. venous sampling site on nicotine tolerance model selection and parameter estimation

In this modeling study we utilize previously published nicotine pharmacokinetic (PK) and pharmacodynamic (PD, heart rate) data to investigate the influence of PK sampling site (venous vs. arterial) on the selection of a specific PD tolerance model and estimation of its parameters. We describe a general model for tolerance which includes as special cases feedback (TF), and kinetic based tolerance (TK) models. A TK model has arterial plasma drug concentrations (Ca) driving (hypothetical) effect (Ce) and antagonist (Cm) site concentrations, which drive a non-feedback effect (Enf): tolerance depends on the relative rate of equilibration of Ce and Cm with Ca. The TF model adds feedback which makes tolerance depend on Enf, not just on drug kinetics for nicotine. The arterial-sampling-analysis (PKPDa) has Ca driving Ce and Cm. The venous-sampling-analysis (PKPDv) does the same but estimates Ca from venous data by means of deconvolution. A TF model (with Cm = Ce) was always selected in the PKPDa. According to this model tolerance developed rapidly with a median half-life of 6.6 min, and median decrease of effect due to tolerance of 31%. Different variants of the TF or TK models were selected in the PKPDv. Parameter estimates for PKPDv show higher variability, and, for the TF model, lower rate and extent of tolerance development and threefold increase in EC50. The study shows that (i) TF models are more appropriate than TK models to describe nicotine effect data, (ii) venous sampling may lead to incorrect model selection and inaccurate and imprecise parameter estimation in respect to arterial sampling, and (iii) arterial sampling should be preferred for accurate (non-steady-state) PD modeling.

Endothelin-1: increased plasma clearance, pulmonary affinity and renal vasoconstriction in young smokers

Pulmonary and renal haemodynamics and elimination of endothelin-1 (ET-1) were studied in six young smokers in response to 20 min intravenous infusion of ET-1 (4 pmol kg(-1) min(-1)) after smoking. At 20 min of ET-1 infusion fractional ET-1 extractions in the lungs and kidneys were 60 +/- 2 and 60 +/- 7%, respectively. Cardiac output and renal blood flow (RBF) fell by 18 +/- 4% (P<0.05) and 34 +/- 5% (P<0.01). Mean systemic arterial pressure increased (P<0.05) whereas pulmonary pressures were unchanged. Compared with previously published data in non-smokers (Weitzberg et al., 1991, 1993) basal arterial ET-1 and ET-1-values during ET-1 infusion were lower with a more rapid return to basal value. Smokers had higher pulmonary extraction of ET-1 at the same pulmonary arterial concentration (P<0.05). RBF reduction was more pronounced (P<0.05). Systemic vascular resistance increased while pulmonary vascular resistance did not increase as in non-smokers. Increased plasma clearance and more efficient pulmonary elimination of ET-1 lowers the arterial level in young smokers. In addition ET-1 evokes more pronounced renal vasoconstriction in these individuals.

Brain imaging and the effects of caffeine and nicotine

Caffeine and nicotine are the most common psychostimulant drugs used worldwide. Structural neuroimaging findings associated with caffeine and nicotine consumption are limited and primarily reflect the putative relationship between smoking and white matter hyperintensities (WMH), a finding that warrants further appraisal of its clinical implications. The application of newer brain imaging modalities that measure subtle haemodynamic changes or tissue-based chemistry in order to better elucidate brain functional processes, including mechanisms underlying addiction to nicotine and caffeine and the brain functional consequences, provide intriguing findings. Potential influences of caffeine and nicotine on the functional contrast, or metabolic response, to neural activation also necessitates the careful appraisal of the effects that these commonly used drugs may have on the results of functional imaging.

Cardiovascular and mood responses to quantified doses of cigarette smoke in oral contraceptive users and nonusers

Previous research suggests that the female sex hormones may moderate cardiovascular and mood responses to cigarette smoking and abstinence. To test this possibility, acute effects of cigarette smoking on cardiovascular reactivity and mood were examined in 12 oral contraceptive users and 12 nonusers across two menstrual phases (early and late cycle). After overnight deprivation, each participant attended two sessions in which they first sham-smoked and then smoked two standard cigarettes, via a quantified smoke delivery system. Oral contraceptive users exhibited larger cigarette smoking-induced increases in heart rate compared with nonusers. In addition, cigarette smoking-induced cardiovascular changes varied with both the phase of the menstrual cycle and oral contraceptive use. No menstrual phase-dependent effects were observed for tobacco withdrawal symptoms, premenstrual symptoms, or moods prior to smoking. Cardiovascular hyperreactivity to cigarette smoke in oral contraceptive users may help explain the mechanisms by which smoking and oral contraceptive use contribute to an elevated risk for coronary heart disease.

Urinary Cotinine and Exposure to Parental Smoking in a Population of Children with Asthma

Background: Studies of the effects of tobacco smoke often rely on reported exposure to cigarette smoke, a measure that is subject to bias. We describe here the relationship between parental smoking exposure as assessed by urinary cotinine excretion and lung function in children with asthma.

Methods: We studied 90 children 4–14 years of age, who reported a confirmed diagnosis or symptoms of asthma. In each child, we assessed baseline pulmonary function (spirometry) and bronchial responsiveness to carbachol stimulation. Urinary cotinine was measured by HPLC with ultraviolet detection.

Results: Urinary cotinine concentrations in the children were significantly correlated (P &lt;0.001) with the number of cigarettes the parents, especially the mothers, smoked. Bronchial responsiveness to carbachol (but not spirometry test results) was correlated (P &lt;0.03) with urinary cotinine in the children.

Conclusion: Passive smoke exposure increases the bronchial responsiveness to carbachol in asthmatic children.

Nicotine is more efficient than cotinine at passing the blood-brain barrier in rats

1. Nicotine and its main metabolite, cotinine, were reported to have distinct behavioral activities in mammals. 2. In this study, cotinine was synthesized without detectable nicotine contamination to compare the ability of nicotine and cotinine to pass the blood-brain barrier (BBB) in rats. 3. The alkaloids were extracted from plasma and brain tissues by methanol, identified by thin-layer chromatography, and quantified by high-pressure liquid chromatography and radioimmunoassays. 4. Consistently, the three methods showed that the passage of cotinine was time, route of administration, and dose dependent and that nicotine was more efficient than cotinine to pass the BBB. 5. The results suggest that these alkaloids may have central activities that probably result from their actions at distinct molecular levels.

Desensitization and resensitization of norepinephrine release in the rat hippocampus with repeated nicotine administration

Desensitization of norepinephrine release was investigated with repeated intravenous (i.v.) infusions of nicotine and in vivo microdialysis of the hippocampus. At 100 min intervals, rats received three infusions of one of the following doses of nicotine: 0.045, 0.09 or 0.135 mg/kg. Doses of 0.09 mg/kg or higher increased norepinephrine release (F= 2.41, P < 0.05). However, the norepinephrine response to the second or third infusion was significantly reduced, compared to the first. The extent of desensitization and rate of resensitization was investigated further by administering consecutive infusions of nicotine (0.135 mg/kg) 40, 60, 100 or 200 min apart. Less norepinephrine was released after a second nicotine infusion given 40 to 100 min later, but this was not reduced further by a third infusion. Norepinephrine release was unchanged with a 200 min inter-infusion interval. Therefore, in the hippocampus, maximal desensitization of nicotine-stimulated norepinephrine release occurs as early as 40 min and persists for at least 100 min; thereafter, resensitization becomes the dominant process.

Immunodetection of cotinine protein in granulosa-lutein cells of women exposed to cigarette smoke

OBJECTIVE

To detect immunoreactivity to cotinine protein, a major metabolite of nicotine, in granulosa-lutein cells from patients exposed to cigarette smoke, as measured by levels of cotinine in follicular fluid (FF) samples.

DESIGN

Controlled immunocytochemical study.

SETTING

Hospital IVF-ET program treating infertile patients.

PATIENT(S)

Twenty-eight women classified by self-reported smoking habits: active smokers (n = 17), passive smokers (n = 4), and nonsmokers (n = 7).

INTERVENTION(S)

Ovarian hyperstimulation.

MAIN OUTCOME MEASURE(S)

Grades of immunostaining intensity were assessed in granulosa-lutein cells. Patient scores of cell immunostaining were calculated and regressed on levels of FF cotinine.

RESULT(S)

Cotinine levels in FF were higher in active smokers than in passive smokers or nonsmokers. Cotinine immunostaining was visualized in the nucleus and cytoplasm of granulosa-lutein cells. Mean grades and mean scores of immunostaining intensity were higher in active smokers than in passive smokers or nonsmokers. There was a strong positive correlation between scores of cell immunostaining and FF cotinine levels.

CONCLUSION(S)

The association between cotinine expression in granulosa-lutein cells and FF cotinine provides reliable evidence for a dose-related effect. This constituent of cigarette smoke appears to interact directly with and incorporate into these ovarian cells. Our approach seems useful for monitoring ovarian exposure to environmental toxins.

Nicotine and sympathetic neurotransmission

Nicotine increases heart rate, myocardial contractility, and blood pressure. These nicotine-induced cardiovascular effects are mainly due to stimulation of sympathetic neurotransmission, as nicotine stimulates catecholamine release by an activation of nicotine acetylcholine receptors localized on peripheral postganglionic sympathetic nerve endings and the adrenal medulla. The nicotinic acetylcholine receptor is a ligand-gated cation channel with a pentameric structure and a central pore with a cation gate, which is essential for ion selectivity and permeability. Binding of nicotine to its extracellular binding site leads to a conformational change of the central pore, which results in the influx of sodium and calcium ions. The resulting depolarization of the sympathetic nerve ending stimulates calcium influx through voltage-dependent N-type calcium channels, which triggers the nicotine-evoked exocytotic catecholamine release. In the isolated perfused guinea-pig heart, cardiac energy depletion sensitizes cardiac sympathetic nerves to the norepinephrine-releasing effect of nicotine, as indicated by a leftward shift of the concentration-response curve, a potentiation of maximum transmitter release, and a delay of the tachyphylaxis of nicotine-evoked catecholamine release. This sensitization was also shown to occur in the human heart under in vitro conditions. Through the intracardiac release of norepinephrine, nicotine induces a beta-adrenoceptor-mediated increase in heart rate and contractility, and an alpha-adrenoceptor-mediated increase in coronary vasomotor tone. The resulting simultaneous increase in oxygen demand and coronary resistance has a detrimental effect on the oxygen balance of the heart, especially in patients with coronary artery disease. Sensitization of the ischemic heart to the norepinephrine-releasing effect of nicotine may be a trigger for acute cardiovascular events in humans, such as acute myocardial infarction and/or life-threatening ventricular tachyarrhythmias.

Dissociating the nicotine and airway sensory effects of smoking

This study examined the subjective and cardiovascular effects of two of the components of cigarette smoking when given separately: nicotine and airway sensations. Using a within-subjects design, six healthy volunteer smokers, age 18-45 years, who smoked at least 20 cigarettes per day were given six conditions in a randomized, counterbalanced order. The effects of IV nicotine, IV saline, and denicotinized cigarettes were compared to a standard 1-mg cigarette. The standard cigarette produced more of a calming effect and more irritability reduction than either the nicotine or airway sensations alone. The denicotinized cigarette was similar to the standard cigarette condition, except the cigarette condition was associated with higher feelings of "exhilaration." Many of the positive subjective effects from a denicotinized cigarette were comparable to that of a standard cigarette. These data support the hypothesis that replacement of the sensory cues of smoking with "airway sensory replacement" may be useful for smoking cessation.

Acute tolerance to nicotine in smokers: lack of dissipation within 2 hours

Greater understanding of development and dissipation of acute tolerance to nicotine may help explain temporal patterns of nicotine self-administration in smokers. The time course of dissipation of acute tolerance to nicotine was examined in 16 smokers (8M, 8F) participating in four sessions differing on pretreatment exposure or time interval prior to nicotine (20 micrograms/kg) challenge: placebo 30 min before, or nicotine (20 micrograms/kg) 30, 60, or 120 min before challenge. Nicotine and placebo were administered by measured-dose nasal spray. The measurement battery consisted of subjective, cardiovascular, thermal pain detection, and behavioral performance measures. Results demonstrated significant acute tolerance (i.e. smaller responses to nicotine challenge following nicotine versus placebo pretreatment) for most subjective measures and for heart rate. Acute tolerance dissipated with lengthening inter-dose interval for two subjective measures, dose strength and arousal, but there was no tolerance dissipation for other measures. In contrast, nicotine pretreatment resulted in acute sensitization of finger temperature (vasoconstriction) response, which dissipated with lengthening interval. No acute tolerance was observed for thermal pain detection or performance measures. These findings demonstrate that acute tolerance develops quickly to some subjective and cardiovascular effects of nicotine. However, acute tolerance to most effects did not dissipate over 2 h, suggesting that, following acute tolerance development during initial exposure, most smokers generally obtain similar magnitude of effects from each subsequent nicotine exposure (i.e. cigarettes smoked later in the day).

Acute pharmacodynamic tolerance to the subjective effects of cigarette smoking

A brief feeling state questionnaire was completed before and after each cigarette, over a day of smoking. Feelings of stress/anxiety demonstrated a pattern of repetitive vacilation over the day, with high stress before smoking, reduced stress after smoking, and stress levels increasing again between cigarettes. There was no evidence of acute pharmacodynamic tolerance, with cigarettes leading to altered feelings of anxiety/stress over the whole day of smoking. Self-rated feelings of arousal also demonstrated a pattern of vacilation over the day, with low arousal pre-smoking increased arousal post-smoking, but arousal levels reducing again between cigarettes. The ANOVA drug x time interaction was significant, with the greatest arousal change following the first cigarette of the day. However, later cigarettes led to similar amounts of arousal change over the rest of day, thus questioning whether acute pharmacodynamic tolerance was occurring. Instead, the heightened arousal response to the first cigarette of the day may reflect the influence of two other factors. Firstly, overnight deprivation, with the first cigarette of the day leading to the greatest increase in plasma nicotine. Secondly, low early-morning arousal with its associated potential for increased arousal. Overall, therefore, there was little indication of acute pharmacodynamic tolerance to the subjective effects of nicotine. Cigarettes were associated with altered feelings of stress and arousal, over the whole day of smoking.

Variables affecting nicotine metabolism

Nicotine metabolism is exceedingly sensitive to perturbation by numerous host factors. To reduce the large variations and discrepancies in the literature pertaining to nicotine metabolism, investigators in future studies need to recognize and better control these host factors. Recent advances in the understanding of nicotine metabolism have suggested new approaches to elucidating underlying mechanisms of certain toxic effects associated with cigarette smoking.

Nicotine transdermal systems

OBJECTIVE

To review the role of transdermal nicotine as an aid to smoking cessation.

DATA SOURCES

A MEDLINE search was performed that included clinical studies published in English involving transdermal nicotine; references used in those articles were screened for additional published information.

STUDY SELECTION

Published clinical trials were reviewed with particular emphasis on controlled trials that evaluated safety and efficacy.

DATA SYNTHESIS

Transdermal nicotine therapy has been shown to be a safe and effective pharmacologic aid in a smoking cessation program when used in conjunction with a psychologic or behavior support system. Habitrol, Nicoderm, Nicotrol, and PROSTEP differ in some characteristics (i.e., delivery systems, total nicotine content and amount absorbed, rate of delivery, recommended duration of application); however, the clinical implication of these differences has not been determined.

CONCLUSIONS

Transdermal nicotine is effective for patients who are motivated to quit smoking and receive concomitant behavior support.

A clinical pharmacological study of subcutaneous nicotine

The stable isotope-labeled compound 3',-3'-dideuteronicotine (nicotine-d2) was used to investigate the disposition kinetics and effects of nicotine administered subcutaneously to 6 smokers. Plasma nicotine-d2 concentrations were measured for 8 h after subcutaneous injection of 4 doses (0.4, 0.8, 1.2, and 2.4 mg). Peak plasma nicotine concentration correlated well with the dose, averaging 2.8 to 14.8 ng/ml, 19 to 25 min after injection of the 0.4 mg and 2.4 mg doses, respectively. The plasma clearance over bioavailability ratio (CL/f) averaged 12 to 13 ml.min-1.kg-1, similar to the clearance reported previously for intravenously administered nicotine. Thus, bioavailability appears to be approximately 100%. The heart rate response was more sensitive to the nicotine dose than the blood pressure response. Subjective effects showed large interindividual variability. The results reported herein may be useful in planning future studies. Administration of nicotine by the subcutaneous route appears to be a practical and safe method for studying the human pharmacology of nicotine.

Smoking and decreased fertilisation rates in vitro

To examine possible mechanisms for the association between cigarette smoking and reduced fertility, we have measured the concentration of the nicotine metabolite cotinine in ovarian follicular fluid collected at the time of oocyte recovery during treatment for in-vitro fertilisation. In a group of women in whom follicular fluid cotinine could not be detected (limit of accurate measurement 20 ng/ml) 116 oocytes were collected, of which 84 became fertilised (72%), whereas among women with cotinine concentration greater than 20 ng/ml 20/45 (44%) oocytes did so (p < 0.01). The median fertilisation rates for individuals (range 1-8 eggs each) in the high and low cotinine groups were 57% and 75%, respectively (p < 0.05). These findings suggest that infertile women should be advised to stop or reduce smoking generally, and especially before treatment by in-vitro fertilisation.

A physiologically based pharmacokinetic model for nicotine disposition in the Sprague-Dawley rat

A physiologically based pharmacokinetic (PBPK) model was developed to describe the disposition of nicotine in the Sprague-Dawley (SD) rat. Parameters for the model were either obtained from the literature (blood flows, organ volumes) or determined experimentally (partition coefficients). Nicotine metabolism was defined in the liver compartment by the first-order rate constants KNC and KNP which control the rate of nicotine metabolism to cotinine and "polar metabolites" (PM), respectively. These rate constants were estimated by optimizing the model fit to pharmacokinetic data obtained by administering an intraarterial (S)-[5-3H]nicotine bolus of 0.1 mg/kg to 6 rats. Model simulations that optimized for the appearance of cotinine in plasma estimated KNC and KNP to be 75.8 and 24.3 hr-1, respectively. Use of these constants in the model allowed us to accurately predict nicotine plasma kinetics and the fraction of the dose eliminated by renal (8.5%) and metabolic (91.5%) clearance. To validate the model's ability to predict tissue kinetics of nicotine, 21 male SD rats were administered 0.1 mg/kg (S)-[5-3H]nicotine intraarterially. At seven time points following treatment, 3 rats were euthanized and tissues were removed and analyzed for nicotine. Model-predicted nicotine tissue kinetics were in agreement with those determined experimentally in muscle, liver, skin, fat, and kidney. The brain, heart, and lung exhibited nonlinear nicotine elimination, suggesting that saturable nicotinic binding sites may be important in nicotine disposition in these organs. Inclusion of saturable receptor binding expressions in the mathematical description of these compartments resulted in better agreement with the experimental data. The Bmax and KD estimated by model simulations for these tissues were brain, 0.009 and 0.12; lung, 0.039 and 2.0; and heart, 0.039 nmol/tissue and 0.12 nM, respectively. This PBPK model can successfully describe the tissue and plasma kinetics of nicotine in the SD rat and will be a useful tool for pharmacologic studies in humans and experimental animals that require insight into the plasma or tissue concentration-effect relationship.

Cigarette smoking and nicotine addiction

Smokers smoke in large part because of the addictive effects of nicotine. Nicotine affects mood and performance and has been clearly implicated as the source of addiction to tobacco. People smoke to deliver desired doses of nicotine to their bodies, with certain rates of delivery and intervals between doses; these behaviors tend to be consistent for a person from day to day. Rational treatment of the pharmacologic aspects of tobacco addiction includes nicotine substitution therapy. New formulations of nicotine substitutes will provide more options to the physician for tailoring treatment to the needs of individual smokers. Other pharmacotherapies, particularly antidepressant drugs, hold promise for certain smokers.

The role of vasopressin in the nicotine-induced stimulation of ACTH and cortisol in men

Experimental evidence indicates that arginine vasopressin (AVP) contributes to the release of ACTH under certain conditions. The present study investigates the role of vasopressin as a secretagogue of ACTH during cigarette smoking or nicotine infusion with additional injection of corticotropin releasing hormone (CRH) and using the specific AVP antagonist d(CH2)5Tyr(Me)-AVP. We first tested the effect of the AVP antagonist (10 micrograms/kg body weight i.v.) on ACTH and cortisol release following cigarette smoking in 15 healthy young male smokers. Smoking led to marked increments in plasma nicotine and to a small rise in plasma ACTH and cortisol. Mean plasma ACTH and cortisol levels were at no time significantly altered by the antagonist. This might be due to a slight agonistic effect of the AVP antagonist, to high interindividual variability of the ACTH and cortisol responses after smoking or to a negligible role of AVP in smoking-induced ACTH release. In a second study we performed the following tests in six healthy male non-smokers: (1) nicotine infusion (1.0 micrograms/kg body weight per min); (2) CRH i.v. (100 micrograms); (3) AVP antagonist i.v. (5 micrograms/kg); (4) nicotine infusion plus CRH i.v.; (5) nicotine infusion plus AVP antagonist i.v.; (6) nicotine infusion plus CRH and AVP antagonist i.v.; and (7) sham infusion. Nicotine infusion led to greater increments of AVP, ACTH and cortisol than smoking without causing nausea. Peak nicotine levels after nicotine infusion were lower than after smoking. The AVP antagonist in the reduced dosage given alone had no effect on hormone levels. However, it slightly attenuated the effect of nicotine on ACTH and cortisol (P less than 0.05, ANOVA).(ABSTRACT TRUNCATED AT 250 WORDS)

Persistent decrease in heart rate after smoking cessation: a 1-year follow-up study

The heart rate of 11 smokers was collected throughout their first year of abstinence. One day after smoking cessation, we recorded a significant mean heart rate drop of 9.07 beats per min, from 74.18 to 65.11 beats per min. No significant variation was afterwards detected at any chosen time point (week 1, 2, 3, 4, 6, month 3, 6, 12). In fact, 1 year after cessation the mean heart rate was still 66.36 beats per min, well below initial baseline values. These data indicate that the decrease in heart rate following smoking cessation mostly represents a permanent return to individual normal values in the absence of nicotine self-administration. Nonetheless, three subjects did show a trend toward the recovery of their precessation heart rate and one subject fully recovered it between months 3 and 6 of abstinence. This trend suggests that, while heart rate adaptation to nicotine is largely of an acute nature, there may also be a chronic component. Its role, though usually minor, should become detectable in a few subjects, because of wide interindividual variability.

Research on stress and smoking: progress and problems

Despite evidence that smoking behaviour increases in the context of stress, there has yet to be a clear-cut demonstration that nicotine intake is similarly enhanced. Although nicotine intake has been shown to reduce reported anxiety in the context of stress, the controlling conditions (type of stressor, intensity, temporal relationships, etc.) need further exploration. Recent findings involving nicotine's effects on the hypophyseal-adrenal axis provide a new perspective on these issues, in that increased nicotine intake during exposure to a stressor may represent, at least in part, behavioral compensation for diminished sensitivity to nicotine brought about by nicotine-stimulated corticosteroid release. Corticosteroids may decrease central nervous system excitability in a way that could account for anxiety reduction; on the other hand, anxiety reduction may be an epiphenomenon with respect to the reinforcement of smoking behaviour. The integration of behavioural, physiological, and biochemical research exemplified by the above approach should lead to a better understanding of stress and smoking.

Cigarette classification as a consumer message

Cigarette yields of tar, nicotine, and carbon monoxide, obtained by standard smoking machine procedures, have been adopted as official consumer information throughout the world. However, real-life dynamics of cigarette puffing and inhalation are not standard, but follow widely fluctuating individual behavior. In addition, smokers inhale after puffing, an event that standard smoking machines do not address. Clearly then, analytical cigarette yields alone are insufficient as quantitative predictors of smoke intake valid for all smokers. Bioavailability studies show that virtually all cigarettes, regardless of analytical yield, can satisfy the nicotine demand of any smoker. On the other hand, tar intake and nicotine intake are related according to the tar-to-nicotine ratio of the smoke, which varies with brands. Thus, while a generalized message predictive of quantitative individual intake is not feasible, tar-to-nicotine ratios of standard analytical yields tell any smoker about expectations of proportional tar intake from different brands, and should be adopted as the preferred consumer message.

Exposure to environmental tobacco smoke (ETS) and serum thiocyanate level in infants

The authors measured the concentrations of serum thiocyanate (SCN) of 80 infants in Chang-Ning District, Shanghai, People's Republic of China. The infants were classified into one of three groups according to the total number of cigarettes family members collectively smoked per day: (1) unexposed, (2) lightly exposed (1-19 cigarettes/d), and (3) heavily exposed (20+ cigarettes/d). The serum SCN levels (mean +/- SD, mumol/l) were 27.7 +/- 10.72 for the unexposed group, 31.9 +/- 13.5 for the lightly exposed group, and 36.2 +/- 14.88 for the heavily exposed group. The concentrations in the heavily exposed group were significantly higher than those in the unexposed group (Z = 2.12, p less than .05). Environmental exposure to tobacco smoke accounted for 5.3% of total variance of the SCN levels after adjusting the effects of father's education level and type of feeding. It is concluded that passive exposure to cigarette smoke in the household results in higher levels of serum SCN in infants.

Effect of cimetidine and ranitidine on the hepatic and renal elimination of nicotine in humans

In a randomized, double-blind, cross-over experiment, 6 healthy consenting male subjects were administered cimetidine 600 mg or ranitidine 300 mg or placebo p.o. q12h x 2 days. Nicotine bitartrate was administered i.v. on day 2 (1 microgram/kg/min) x 30 min. After cimetidine mean nicotine total and metabolic clearances were decreased by 30% and 27% while after ranitidine the clearances were decreased by 10% and 7% respectively. Since smokers regulate their smoke intake based in large part on their nicotine blood levels these results suggest that the diminished nicotine total clearance in the presence of cimetidine could be important in assisting smoking reduction or cessation.

Development of central and peripheral smoking effects over time

The present study compared for the first morning cigarettes CO and nicotine absorption as well as the effects on EEG and peripheral functions across a period of 90 min. Eighteen smokers participated in two sessions, one in which they smoked two cigarettes in succession and another in which they smoked three cigarettes at 30-min intervals. Smoking two cigarettes in succession produced a particularly wide range in nicotine absorption so that the subjects could be grouped into high (HN) and low (LN) nicotine absorbers, differing significantly in their CO and nicotine absorption. The smoking-induced cardioacceleration was greater and lasted longer in the HN than in the LN group. While the dominant alpha frequency increased to a significant extent in the HN group only, beta power increased in both groups, alpha power remained unaffected, theta power decreased in the HN group only and the effects on heart rate, dominant alpha frequency and beta power were significantly correlated with nicotine absorption across both groups. Smoking three cigarettes at 30-min intervals produced qualitatively similar but generally smaller effects. However, neither nicotine uptake nor any of the physiological parameters showed differential developments between the two groups, except the dominant alpha frequency, which increased in the HN group only. The development of acute tolerance to smoking across three cigarettes was observed only for finger vasoconstriction, craving to smoke and sickness after smoking, but not for cardioacceleration or any EEG parameters.

The effects of smoking on the mood, cardiovascular and adrenergic reactivity of heavy and light smokers in a non-stressful environment

Following a period of overnight deprivation, 58 smokers participated in a 90-min laboratory assessment in which they viewed a non-stressful movie and smoked two 0.5-mg nicotine-containing cigarettes. The first cigarette was given to all subjects following 25 min of adaptation and baseline. The next cigarette was provided at their request, which occurred 9-12 min later. "Heavy" and "light" smokers were grouped according to their average morning cotinine values, which fell above or below 250 ng/ml, respectively. The results showed that, relative to their baseline, heavy and light smokers experienced about the same level of post-smoking change in blood nicotine, heart rate and blood pressure. However, heavy smokers showed a significantly greater delta from baseline in post-smoking measures of epinephrine, norepinephrine, tension reduction and increase in vigor enhancement. A strong and consistent correlation was observed between post-smoking increases in epinephrine, tension reduction and increased vigor.