Nicotine addiction

Nicotine receptor partial agonists for smoking cessation

BACKGROUND

Nicotine receptor partial agonists may help people to stop smoking by a combination of maintaining moderate levels of dopamine to counteract withdrawal symptoms (acting as an agonist) and reducing smoking satisfaction (acting as an antagonist). Varenicline was developed as a nicotine receptor partial agonist from cytisine, a drug widely used in central and eastern Europe for smoking cessation. The first trial reports of varenicline were released in 2006, and further trials have now been published or are currently are underway.

OBJECTIVES

The primary objective of this review is to assess the efficacy and tolerability of nicotine receptor partial agonists, including varenicline and cytisine, for smoking cessation.

SEARCH STRATEGY

We searched the Cochrane Tobacco Addiction Group's specialised register for trials, using the terms ('varenicline' or 'cytisine' or 'Tabex' or 'nicotine receptor partial agonist') and 'smoking' in the title or abstract, or as keywords. We also searched MEDLINE, EMBASE, PsycINFO and CINAHL using MeSH terms and free text, and we contacted authors of trial reports for additional information where necessary. The latest search was in March 2008.

SELECTION CRITERIA

We included randomized controlled trials which compared the treatment drug with placebo. We also included comparisons with bupropion and nicotine patches where available. We excluded trials which did not report a minimum follow-up period of six months from start of treatment.

DATA COLLECTION AND ANALYSIS

We extracted data in duplicate on the type of participants, the dose and duration of treatment, the outcome measures, the randomization procedure, concealment of allocation, and completeness of follow up. The main outcome measured was abstinence from smoking after at least six months from the beginning of treatment. We used the most rigorous definition of abstinence, and preferred biochemically validated rates where they were reported. Where appropriate we performed meta-analysis to produce a risk ratio, using the Mantel-Haenszel fixed-effect model.

MAIN RESULTS

We found seven trials of varenicline compared with placebo for smoking cessation; three of these also included a bupropion experimental arm. We found one relapse prevention trial, comparing varenicline with placebo. We also found one open-label trial comparing varenicline with nicotine replacement therapy. The nine trials covered 7267 participants, 4744 of whom used varenicline. We identified one trial of cytisine (Tabex) for inclusion. The pooled risk ratio (RR) for continuous abstinence at six months or longer for varenicline versus placebo was 2.33 (95% confidence interval [CI] 1.95 to 2.80). The pooled RR for varenicline versus bupropion at one year was 1.52 (95% CI 1.22 to 1.88). The RR for varenicline versus NRT at one year was 1.31 (95% CI 1.01 to 1.71). The two trials which tested the use of varenicline beyond the 12-week standard regimen found the drug to be well-tolerated during long-term use. The main adverse effect of varenicline was nausea, which was mostly at mild to moderate levels and usually subsided over time. Post-marketing safety data suggest that varenicline may be associated with depressed mood, agitation, and suicidal behaviour or ideation. The labelling of varenicline has been amended, and the FDA is conducting a safety review. The one cytisine trial included in this review found that more participants taking cytisine stopped smoking compared with placebo at two-year follow up, with an RR of 1.61 (95% CI 1.24 to 2.08).

AUTHORS' CONCLUSIONS

Varenicline increased the chances of successful long-term smoking cessation between two- and threefold compared with pharmacologically unassisted quit attempts. More participants quit successfully with varenicline than with bupropion. One open-label trial of varenicline versus nicotine replacement therapy demonstrated a modest benefit of varenicline. The effectiveness of varenicline as an aid to relapse prevention has not been clearly established. The main adverse effect of varenicline is nausea, but mostly at mild to moderate levels and tending to subside over time. Possible links with serious adverse events, including depressed mood, agitation and suicidal thoughts, are currently under review. There is a need for independent community-based trials of varenicline, to test its efficacy and safety in smokers with varying co-morbidities and risk patterns. There is a need for further trials of the efficacy of treatment extended beyond 12 weeks. Cytisine may also increase the chances of quitting, but the evidence at present is inconclusive.

Chronic nicotine exposure has dissociable behavioural effects on control and beta2-/- mice

Nicotine exerts beneficial effects on various neurological and psychiatric pathologies, yet its effects on cognitive performance remain unclear. Mice lacking the beta2 subunit of the nicotinic receptor (beta2-/-) show characteristic deficits in executive functions and are suggested as reliable animal models for some specific endophenotypes of human pathologies, notably ADHD. We use beta2-/- and their controls to investigate the consequences of chronic nicotine exposure on cognitive behaviour. We show that in control mice, this treatment elicits somewhat slight effects, particularly affecting nocturnal activity and self-grooming. By contrast, in beta2-/- mice, chronic nicotine treatment had restorative effects on exploratory behaviour in the open-field and affected rearing, but did not modify motor functions. We confirmed that beta2-/- mice exhibit impaired exploratory and social behaviour, and further demonstrated their nocturnal hyperactivity. These data support the proposal that beta2-/- mice represent a relevant model for cognitive disorders in humans and that nicotine administered chronically at low dose may relieve some of these.

Tobacco addiction

Tobacco use is associated with 5 million deaths per year worldwide and is regarded as one of the leading causes of premature death. Comprehensive programmes for tobacco control can substantially reduce the frequency of tobacco use. An important component of a comprehensive programme is the provision of treatment for tobacco addiction. Treatment involves targeting several aspects of addiction including the underlying neurobiology and behavioural processes. Furthermore, building an infrastructure in health systems that encourages and helps with cessation, as well as expansion of the accessibility of treatments, is necessary. Although pharmacological and behavioural treatments are effective in improving cessation success, the rate of relapse to smoking remains high, emphasising the strong addictive nature of nicotine. The future of treatment resides in improvement in patient matching to treatment, combination or novel drugs, and viewing nicotine addiction as a chronic disorder that might need long-term treatment.

Neurobiology of nicotine addiction: implications for smoking cessation treatment

Nicotine sustains addictive tobacco use, which in turn causes much premature disability and death. The essence of drug addiction is loss of control of drug use. Molecular biology studies suggest that the alpha(4)beta(2) nicotinic acetylcholine receptor subtype is the main receptor mediating nicotine dependence. Nicotine acts on these brain nicotinic cholinergic receptors to facilitate neurotransmitter release (dopamine and others), producing pleasure, stimulation, and mood modulation. Neuroadaptation develops with repeated exposure to nicotine, resulting in tolerance to many of the effects of nicotine. When a smoker stops smoking, a nicotine withdrawal syndrome ensues, characterized by irritability, anxiety, increased eating, dysphoria, and hedonic dysregulation, among other symptoms. Smoking is also reinforced by conditioning, such that specific stimuli that are psychologically associated with smoking become cues for an urge to smoke. These include the taste and smell of tobacco, as well as particular moods, situations, and environmental cues. Pharmacotherapies to aid smoking cessation should ideally reduce nicotine withdrawal symptoms and block the reinforcing effects of nicotine obtained from smoking without causing excessive adverse effects. Further, given the important role of sensory effects of smoking and psychoactive effects of nicotine, counseling and behavioral therapies are important adjuncts to and substantially augment the benefits of pharmacotherapy.

Self-administration of intravenous nicotine in male and female cigarette smokers

Although nicotine is the main addictive chemical in tobacco, there have been few studies of pure nicotine self-administration in humans. The goal of this study was to test the parameters of an intravenous (IV) nicotine self-administration model using nicotine doses presumed to be within the range of those of average intake from cigarette smoking. Six male and four female smokers participated in a double-blind, placebo-controlled, crossover study, which consisted of one adaptation and three experimental sessions. In each experimental session, subjects were randomly assigned to one of the three doses of nicotine (0.1, 0.4, or 0.7 mg). The lowest nicotine dose, 0.1 mg, was chosen to be approximately half the amount of nicotine inhaled from one puff of a cigarette. During each experimental session, subjects first sampled the assigned nicotine dose and placebo and then had the opportunity to choose between nicotine and placebo for a total of six choices over a 90-min period. Out of six options, the average (SEM) number of nicotine choices were 3.0 (0.48) for 0.1 mg, 4.7 (0.48) for 0.4 mg and 4.5 (0.46) for 0.7 mg, indicating a significant effect of nicotine dose on nicotine choice. Both the 0.4 and 0.7, but not the 0.1 mg, nicotine doses were preferred to placebo. These higher doses also produced increases in heart rate, blood pressure, and ratings of drug liking and high. Overall, these findings indicate that smokers chose both the 0.4 and the 0.7 mg nicotine doses over placebo. Our model may be useful in the evaluation of the effects of both behavioral and pharmacological manipulations on nicotine self-administration in humans.

Bupropion inhibits the cellular effects of nicotine in the ventral tegmental area

Each year, tobacco use causes over 4 million deaths worldwide and billions of dollars are spent on treatment for tobacco-related illness. Bupropion, an atypical antidepressant, improves the rates of successful smoking cessation, however, the mechanisms by which bupropion reduces cigarette smoking and depression are unknown. Here we show that clinical concentrations of bupropion inhibit nicotine's stimulatory effects on brain reward areas. Many drugs of abuse, including nicotine, stimulate dopamine (DA) release in the mesoaccumbens reward system. Nicotinic acetylcholine receptors in the ventral tegmental area (VTA) mediate nicotine's stimulation of DA release, as well as its rewarding effects. Nicotinic receptors are expressed by excitatory and inhibitory neurons that control DA neuron excitability, and by the DA neurons themselves. Bupropion is a broad-spectrum non-competitive nicotinic receptor antagonist. Here we report that pre-treatment of brain slices with a clinically relevant concentration of bupropion dramatically reduces the effects of nicotine on DA neuron excitability. Nicotinic receptors on VTA DA neurons and their synaptic inputs are inhibited by 75 - 95% after bupropion treatment. We also find that bupropion alone reduces GABAergic transmission to DA neurons, thereby diminishing tonic inhibition of these neurons. This increases DA neuron excitability during bupropion treatment in the absence of nicotine, and may contribute to bupropion's antidepressant actions.

Varenicline: the newest agent for smoking cessation

PURPOSE

The pharmacology, pharmacokinetics, clinical efficacy, safety, dosage and administration, and place in therapy of varenicline are reviewed.

SUMMARY

Varenicline is the newest therapy approved by the Food and Drug Administration for smoking cessation and the first in its class targeting the neurobiology of nicotine addiction. Varenicline is selective for the alpha4beta2 acetylcholine-receptor subtype as a partial agonist, thus conferring its effect in limiting the reinforcing aspect of the addictive nicotine molecule. Varenicline is completely absorbed orally and not affected by food. Steady state is reached within four days of administration. Three Phase III clinical trials of varenicline have been published. Two studies compared varenicline with bupropion in patients over age 18 years who smoked more than 10 cigarettes daily. When the data of the two trials were pooled, varenicline use was associated with significant improvements in the four-week carbon-monoxide-confirmed continuous quit rate (44.2% at weeks 9-12 compared with bupropion (29.7%) and placebo (17.7%) (p < 0.0001 for each comparison). The third trial found that continuous quit rates were also significantly higher in patients treated with varenicline versus placebo. Varenicline is generally well tolerated. Varenicline has been administered concurrently with warfarin, digoxin, transdermal nicotine, bupropion, cimetidine, and metformin without any clinically significant drug interactions.

CONCLUSION

Varenicline, a newly approved agent for smoking cessation, offers a new option to patients who cannot tolerate the adverse effects associated with nicotine-replacement therapy and bupropion. It is also an alternative to consider in patients with contraindications to such therapies.

Analysis of [3',3'-d(2)]-nicotine and [3',3'-d(2)]-cotinine by capillary liquid chromatography-electrospray tandem mass spectrometry

A selective and sensitive LC/MS/MS assay was developed for the quantification of d(2)-nicotine and d(2)-cotinine in plasma of current and past smokers administered d(2)-nicotine. After solid phase extraction and liquid-liquid extraction, HPLC separation was achieved on a capillary hydrophilic interaction chromatography phase column. The analytes were monitored by tandem mass spectrometry with electrospray positive ionization. Linear calibration curves were generated for d(2)-nicotine (0.03-6.0 ng/ml plasma) and d(2)-cotinine (0.15-25 ng/ml plasma). The lower limits of quantitation were 0.15 ng/ml and 0.25 ng/ml for d(2)-nicotine and d(2)-cotinine, respectively. The coefficient of variation was 3.7% for d(2)-nicotine and 2.5% for d(2)-cotinine. The method was applied to two ongoing studies of d(2)-nicotine metabolism in prior and current smokers. Preliminary analysis of a subset of subjects from these studies detected a significantly lower rate of nicotine conversion to cotinine by past smokers compared to current smokers.

Pharmacological approaches to smoking cessation

Smoking, the most prominent nongenetic factor contributing to mortality, remains the major public health problem throughout the world. There are nearly 1.1 billion users of nicotine and tobacco products worldwide while approximately one third to half of them will die from smoking-related disease. The habit of smoking is mainly propelled by nicotine, a strongly addictive substance, to which the vast majority of smokers fall victim. Except for the general and specific support and counseling strategies there are now effective treatments for nicotine addiction. Two types of pharmacological therapies have been approved and are now licensed for smoking cessation. The first therapy consists of nicotine replacement, substituting the nicotine from cigarettes with safer nicotine formulations. The second therapy is bupropion, an antidepressant of the aminoketone class, which has been demonstrated to be effective in smoking cessation. However, although some cigarette smokers are able to quit, many are not, and standard medications to assist smoking cessation are ineffective. Several agents used for other indications (e.g. neurological diseases, depression, alcoholism) might be used to treat this subgroup. In conclusion, new more effective drugs are needed in order to fight the panepidemic of smoking globally.

Reevaluating the nicotine delivery kinetics hypothesis

RATIONALE

The view of smoking as an addiction to nicotine implies that nicotine is an addictive drug and a primary reinforcer. However, nicotine other than in tobacco does not appear to be very rewarding for smokers. This potential anomaly to the nicotine addiction thesis is resolved by the proposition that the reward associated with smoking depends on "high-nicotine boli." According to the nicotine delivery kinetics hypothesis, smoked nicotine reaches the brain in 5-10 s in high concentrations, which provide reinforcing "hits" of nicotine to the brain.

OBJECTIVES

Because of its essential role in the nicotine addiction thesis, this review set out to examine the current empirical basis of the nicotine delivery kinetics hypothesis.

MATERIALS AND METHODS

We reviewed studies that bear on two questions: First, does nicotine from cigarettes reach the brain significantly faster than from other nicotine delivery devices? Second, is there a relationship between delivery kinetics and any rewarding effects of nicotine?

RESULTS

There is little empirical support for the nicotine delivery kinetics hypothesis. Several studies found that arterial nicotine levels associated with smoking are much lower than predicted by the nicotine delivery kinetics thesis and not higher than with other nicotine delivery devices. More importantly, comparisons of nicotine delivery devices with varying speeds of delivery do not suggest any correlation between nicotine delivery profile and subjective reward.

CONCLUSIONS

This review indicates that the wide endorsement of the nicotine delivery kinetics hypothesis is unjustified. Critical research is required to resolve the anomalies within the nicotine addiction theory of smoking.

Confirmatory factor analyses and reliability of the modified cigarette evaluation questionnaire

We examined the validity and reliability of the modified Cigarette Evaluation Questionnaire (mCEQ) that assesses the degree to which subjects experience the reinforcing effects of smoking. Data came from three phase II clinical trials (n=626, n=627, n=312) on varenicline for smoking cessation. Comparative fit indexes and non-normed fit indexes from a confirmatory factor analysis exceeded 0.90. Cronbach's alpha for internal consistency reliability exceeded 0.70 for the Smoking Satisfaction domain and the Psychological Reward domain but was less than 0.70 for the Aversion domain; test-retest reliability generally exceeded 0.70 on the three multi-item domains and two single items. The validity and, in general, the reliability of the postulated multidimensional framework of the mCEQ are confirmed and supported by the analyses of three independent studies, with multi-item domains on Smoking Satisfaction (satisfying, taste good, enjoy smoking), Psychological Reward (calm down, more awake, less irritable, help concentrate, reduce hunger), and Aversion (dizziness, nauseous), as well as the single-item assessment on Enjoyment of Respiratory Tract Sensations and on Craving Reduction.

Euphoriant effects of nicotine in smokers: fact or artifact?

RATIONALE

The claim that nicotine in cigarettes is euphoriant to smokers is largely based on two studies (Pomerleau and Pomerleau, Psychopharmacology, 108:460-465, 1992; Tobacco Control, 3:374, 1994) in which smokers were instructed to respond to sensations of rush, buzz, or high while smoking low-nicotine or regular cigarettes. However, the assumption that these sensations are pleasurable was not tested and may have biased the results.

OBJECTIVES

The aim of this study was to re-examine the claim that smoked nicotine is euphoriant to smokers.

METHODS

Study 1 surveyed the frequency and pleasantness of the smoking-related sensations of rush, buzz, and high in a sample of smokers. Study 2 replicated Pomerleau and Pomerleau (Psychopharmacology, 108:460-465, 1992) with two sets of instruction. One set, as in the original study, defined these sensations as pleasurable, whereas the other defined them as unpleasant.

RESULTS

Study 1 found that whereas rush and high were perceived as pleasant, buzz was unpleasant to most smokers. Study 2 found that under both sets of instructions, smokers reported more sensations when smoking the regular, as compared to the low-nicotine cigarette. Additionally, the sensations of rush, buzz, and high were rated as more pleasant under the pleasant instructions as compared to the unpleasant instructions. Finally, in the pleasant instructions condition, many participants reported having pressed the button to indicate a pleasurable sensation despite having actually experienced that sensation as unpleasant.

CONCLUSIONS

Our results suggest that the findings of Pomerleau and Pomerleau (Psychopharmacology, 108:460-465, 1992; Tobacco Control, 3:374, 1994) may have been biased by the experimental instructions and cannot be taken as evidence that smoked nicotine is euphoriant to smokers.

Guidelines on nicotine dose selection for in vivo research

RATIONALE

This review provides insight for the judicious selection of nicotine dose ranges and routes of administration for in vivo studies. The literature is replete with reports in which a dosaging regimen chosen for a specific nicotine-mediated response was suboptimal for the species used. In many cases, such discrepancies could be attributed to the complex variables comprising species-specific in vivo responses to acute or chronic nicotine exposure.

OBJECTIVES

This review capitalizes on the authors' collective decades of in vivo nicotine experimentation to clarify the issues and to identify the variables to be considered in choosing a dosaging regimen. Nicotine dose ranges tolerated by humans and their animal models provide guidelines for experiments intended to extrapolate to human tobacco exposure through cigarette smoking or nicotine replacement therapies. Just as important are the nicotine dosaging regimens used to provide a mechanistic framework for acquisition of drug-taking behavior, dependence, tolerance, or withdrawal in animal models.

RESULTS

Seven species are addressed: humans, nonhuman primates, rats, mice, Drosophila, Caenorhabditis elegans, and zebrafish. After an overview on nicotine metabolism, each section focuses on an individual species, addressing issues related to genetic background, age, acute vs chronic exposure, route of administration, and behavioral responses.

CONCLUSIONS

The selected examples of successful dosaging ranges are provided, while emphasizing the necessity of empirically determined dose-response relationships based on the precise parameters and conditions inherent to a specific hypothesis. This review provides a new, experimentally based compilation of species-specific dose selection for studies on the in vivo effects of nicotine.

Nicotine receptor partial agonists for smoking cessation

BACKGROUND

Nicotine receptor partial agonists may help smokers to quit by a combination of maintaining moderate levels of dopamine to counteract withdrawal symptoms (acting as an agonist) and reducing smoking satisfaction (acting as an antagonist). Varenicline was developed as a nicotine receptor partial agonist from cytisine, a drug widely used in central and eastern Europe for smoking cessation. The first trial reports of varenicline were released in 2006, and further trials are underway.

OBJECTIVES

The primary objective of this review is to assess the efficacy and tolerability of nicotine receptor partial agonists, including varenicline and cytisine, for smoking cessation.

SEARCH STRATEGY

We searched the Cochrane Tobacco Addiction Group's specialised register for trials, using the terms ('varenicline' or 'cytisine' or 'Tabex' or 'nicotine receptor partial agonist') and 'smoking' in the title or abstract, or as keywords. We also searched MEDLINE, EMBASE, PsycINFO and CINAHL using MeSH terms and free text, and we contacted authors of trial reports for additional information where necessary. The last search was in October 2006.

SELECTION CRITERIA

We included randomized controlled trials which compared the treatment drug with placebo. We also included comparisons with bupropion where available. We excluded trials which did not report a minimum follow-up period of six months from start of treatment.

DATA COLLECTION AND ANALYSIS

We extracted data in duplicate on the type of participants, the dose and duration of treatment, the outcome measures, the randomization procedure, concealment of allocation, and completeness of follow up. The main outcome measured was abstinence from smoking after at least six months from the beginning of treatment. We used the most rigorous definition of abstinence, and preferred biochemically validated rates where they were reported. Where appropriate we performed meta-analysis using the Mantel-Haenszel fixed-effect model.

MAIN RESULTS

We found five trials of varenicline compared with placebo for smoking cessation; three of these also included a bupropion experimental arm. We also found one relapse prevention trial, comparing varenicline with placebo. The six trials covered 4924 participants, 2451 of whom used varenicline. We identified one trial of cytisine (Tabex) for inclusion. The pooled odds ratio (OR) for continuous abstinence at 12 months for varenicline versus placebo was 3.22 (95% confidence interval [CI] 2.43 to 4.27). The pooled OR for varenicline versus bupropion was 1.66 (95% CI 1.28 to 2.16). The main adverse effect of varenicline was nausea, which was mostly at mild to moderate levels and usually subsided over time. The two trials which tested the use of varenicline beyond the 12-week standard regimen found the drug to be well-tolerated and effective during long-term use. The one cytisine trial included in this review found that more participants taking cytisine stopped smoking compared with placebo at two-year follow up, with an OR of 1.77 (95% CI 1.30 to 2.40).

AUTHORS' CONCLUSIONS

Varenicline increased the odds of successful long-term smoking cessation approximately threefold compared with pharmacologically unassisted quit attempts. In trials reported so far, more participants quit successfully with varenicline than with bupropion. The effectiveness of varenicline as an aid to relapse prevention has not been clearly established. The main adverse effect of varenciline is nausea, but this is mostly at mild to moderate levels and tends to reduce with habituation. There is a need for independent trials of varenicline versus placebo, to test the early findings. There is also a need for direct comparisons with nicotine replacement therapy, and for further trials with bupropion, to establish the relative efficacy of the treatments.Cytisine may also increase the chances of quitting, but the evidence at present is inconclusive.

Weight Gain and Anxiety Levels in Recent Ex-Smokers

OBJECTIVE

To evaluate weight gain and its relation to anxiety in a group of smokers after 3 months of cessation treatment.

PATIENTS AND METHODS

The target population for this prospective, analytical, longitudinal study was smokers being treated in a specialist smoking cessation clinic who were still abstinent at the conclusion of a 3-month treatment program. The following variables were analyzed: age, sex, nicotine dependence (Fagerström test), daily cigarette consumption, number of pack-years, pharmacological treatment (nicotine replacement/bupropion), use of nicotine gum (yes/no), weight gain, body mass index, and degree of state and trait anxiety. Successful cessation was defined as self-reported abstinence confirmed by measurement of expired carbon monoxide (CO) level (< or = 10 ppm). Anxiety was evaluated using the State-Trait Anxiety Inventory. The state anxiety and weight variables were measured on 5 occasions: before smoking cessation, and at the end of week 1, month 1, month 2, and month 3 after cessation. Results for the quantitative variables were expressed as means (SD), and results for the qualitative variables were expressed as percentages and absolute frequencies.

RESULTS

The study population consisted of 122 individuals, 76 of whom were men (62%) and 46 of whom were women (38%). The mean age was 43.9 (9.9) years, and mean nicotine dependence according to the Fagerström scale was 6.2 (2.2) points. Average weight gain was 2.6 kg (3.6%), with no significant difference between the sexes. Weight gain in 25% of this population was greater than 4.2 kg, and maximum weight gain was 9.2 kg. Levels of state anxiety fell progressively as weight increased, although there was no evident relationship between the 2 variables.

CONCLUSIONS

Weight gain is moderate as smokers quit. Anxiety levels, which are greater in the first few weeks after cessation, do not explain weight variation, which is more related to the metabolic effects of nicotine rather than to psychological variables.

Opioid antagonists for smoking cessation

BACKGROUND

The reinforcing properties of nicotine may be mediated through release of various neurotransmitters both centrally and systemically. Smokers report positive effects such as pleasure, arousal, and relaxation as well as relief of negative affect, tension, and anxiety. Opioid (narcotic) antagonists are of particular interest to investigators as potential agents to attenuate the rewarding effects of cigarette smoking.

OBJECTIVES

To evaluate the efficacy of opioid antagonists in promoting long-term smoking cessation. The drugs include naloxone and the longer-acting opioid antagonist naltrexone.

SEARCH STRATEGY

We searched the Cochrane Tobacco Addiction Group specialized register for trials of naloxone, naltrexone and other opioid antagonists and conducted an additional search of MEDLINE using 'Narcotic antagonists' and smoking terms in March 2006. We also contacted investigators, when possible, for information on unpublished studies.

SELECTION CRITERIA

We considered randomized controlled trials comparing opioid antagonists to placebo or an alternative therapeutic control for smoking cessation. We included in the meta-analysis only those trials which reported data on abstinence for a minimum of six months. We also reviewed, for descriptive purposes, results from short-term laboratory-based studies of opioid antagonists designed to evaluate psycho-biological mediating variables associated with nicotine dependence.

DATA COLLECTION AND ANALYSIS

We extracted data in duplicate on the type of study population, the nature of the drug therapy, the outcome measures, method of randomization, and completeness of follow up. The main outcome measure was cotinine- or carbon monoxide-verified abstinence from smoking after at least six months follow up in patients smoking at baseline. Where appropriate, we performed meta-analysis using a fixed-effect model (Mantel-Haenszel odds ratios).

MAIN RESULTS

Four trials of naltrexone met inclusion criteria for meta-analyses for long-term cessation. All four trials failed to detect a significant difference in quit rates between naltrexone and placebo. In a pooled analysis there was no significant effect of naltrexone on long-term abstinence, and confidence intervals were wide (odds ratio 1.26, 95% confidence interval 0.80 to 2.01). No trials of naloxone or buprenorphine reported long-term follow up.

AUTHORS' CONCLUSIONS

Based on limited data from four trials it is not possible to confirm or refute whether naltrexone helps smokers quit. The confidence intervals are compatible with both clinically significant benefit and possible negative effects of naltrexone in promoting abstinence. Data from larger trials of naltrexone are needed to settle the question of efficacy for smoking cessation.

Monoamine oxidase A knockout mice exhibit impaired nicotine preference but normal responses to novel stimuli

Nicotine is thought to act on brain monoamine systems that normally mediate diverse motivational behaviors. How monoamine-related genes contribute to behavioral traits (e.g. responses to novel stimuli) comorbid with the susceptibility to nicotine addiction is still poorly understood. We examined the impact of constitutive monoamine oxidase A (MAOA) deficiency in mice on nicotine reward and responses to novel stimuli. Age-matched, male Maoa-knockout (KO) mice and wild-type (WT) littermates were tested for nicotine-induced conditioned place preference (CPP); voluntary oral nicotine preference/intake; spontaneous locomotor activity in a novel, inescapable open field; and novelty place preference. Nicotine preference in WT mice was reduced in Maoa-KO mice in the CPP and oral preference/intake tests. Control experiments showed that these phenotypes were not due to abnormalities in nicotine metabolism, fluid intake or response to taste. In contrast, Maoa-KO mice were normal in their behavioral response to a novel, inescapable open field and in their preference for a novel place. The observed phenotypes suggest that a constitutive deficiency of MAOA reduces the rewarding effects of nicotine without altering behavioral responses to novel stimuli in mice. Constitutive MAOA activity levels are likely to contribute to the vulnerability or resiliency to nicotine addiction by altering the rewarding effects of nicotine.

The epidemiology of tobacco use and dependence

Tobacco use continues to be a public health issue of great importance. Acute and critical care nurses in particular have a unique opportunity to become a cornerstone for the nation's tobacco control efforts through integration of prevention and cessation interventions as part of patient care. This article provides readers with a working knowledge of tobacco use and dependence as background reading for the subsequent articles presented in this special issue addressing tobacco cessation in acute and critical care settings.

Pharmacologic interventions for smoking cessation

According to the US Public Health Service, all patients attempting to quit smoking should be encouraged to use one or more effective pharmacotherapy agents for cessation except in the presence of special circumstances. This article provides an overview of the pharmacologic agents for acute and critical care nurses to consider when intervening with tobacco-dependent patients. Medications addressed in this article include (1) first-line agents (nicotine replacement therapy, sustained-release bupropion) that have proven efficacy and are approved by the Food and Drug Administration (FDA) for smoking cessation, (2) second-line agents (nortriptyline, clonidine) that have proven efficacy but no FDA indication for smoking cessation, (3) approaches that use of combination or high-dose therapy, (4) herbal therapies, and (5) emerging therapies that are currently under investigation.

Tobacco and its trendy alternatives: implications for pediatric nurses

Although acute and critical care pediatric nurses may not rank tobacco prevention and cessation among their top patient-care priorities, the importance of providing health education, especially during vulnerable moments, cannot be overlooked. This article provides an overview of trendy tobacco alternatives, such as bidis, clove cigarettes, hookah pipes, and smokeless tobacco, that entice youth. The significant health consequences of these tobacco products and the implications for pediatric acute and critical care nursing practice are also discussed.

Neuropsychology and neuropharmacology of P3a and P3b

Perspectives on the P300 event-related brain potential (ERP) are reviewed by outlining the distinction between the P3a and P3b subcomponents. The critical factor for eliciting P3a is how target/standard discrimination difficulty rather than novelty modulates task processing. The neural loci of P3a and P3b generation are sketched and a theoretical model is developed. P3a originates from stimulus-driven disruption of frontal attention engagement during task processing. P3b originates when temporal-parietal mechanisms process the stimulus information for memory storage. The neuropharmacological implications of this view are then outlined by evaluating how acute and chronic use of ethanol, marijuana, and nicotine affect P3a and P3b. The findings suggest that the circuit underlying ERP generation is influenced in a different ways for acute intake and varies between chronic use levels across drugs. Theoretical implications are assessed.

Emerging pharmacological strategies in the fight against cocaine addiction

Cocaine addiction continues to be an important public health problem worldwide. At present, there are no proven pharmacotherapies for cocaine addiction. The studies reviewed here revealed a number of emerging targets for cocaine pharmacotherapy. First, disulfiram, a medication with dopaminergic effects, reduced cocaine use in a number of clinical trials. Second, GABA medications, tiagabine and topiramate, were found promising in clinical trials. Third, a beta-adrenergic blocker, propranolol, may be effective especially among cocaine-addicted individuals with high withdrawal severity. Fourth, treatment with a stimulant medication, modafinil, has reduced cocaine use. Last, a cocaine vaccine that slows entry of cocaine into the brain holds promise. These promising findings need to be further tested in controlled clinical trials.

A neurocomputational hypothesis for nicotine addiction

We present a hypothetical neurocomputational model that combines a set of neural circuits at the molecular, cellular, and system levels and accounts for several neurobiological and behavioral processes leading to nicotine addiction. We propose that combining changes in the nicotinic receptor response, expressed by mesolimbic dopaminergic neurons, with dopamine-gated learning in action-selection circuits, suffices to capture the acquisition of nicotine addiction. We show that an opponent process enhanced by persistent nicotine-taking renders self-administration rigid and habitual by inhibiting the learning process, resulting in long-term impairments in the absence of the drug. The model implies distinct thresholds on the dosage and duration for the acquisition and persistence of nicotine addiction. Our hypothesis unites a number of prevalent ideas on nicotine action into a coherent formal network for further understanding of compulsive drug addiction.

Inclusion of tobacco exposure as a predictive factor for decreased bone mineral content

Tobacco exposure has been implicated as a risk factor for decreased bone density, which might result in osteoporosis. Cotinine, a metabolite of nicotine, is commonly used as a marker for tobacco exposure (active or passive). The objective of the present study was to compare tobacco exposure with other predictive factors for low bone mineral content (BMC), as determined by dual photon bone absorptiometry (DXA) in a national U.S. sample. Publicly available interview and clinical examination data from the Third National Health and Nutrition Examination Survey, 1988-1994 (NHANES-III) were used. Our data included 14,060 subjects from 19,528 randomly selected representative U.S. households. Clinical laboratory data included serum values for calcium and cotinine. BMC was assessed radiologically by DXA at five proximal femur sites. BMC values were adjusted for age, as well as height, weight, and bone area to correct for bone and body size. We used t tests to compare continuous variables and chi-square tests to explore associations between categorical variables. Multivariate regression models were developed for each gender with appropriate covariates. Intertrochanter BMC explained the most variation (highest R2) and was selected as the basis of the comparison. Serum cotinine had a significant inverse relationship to BMC in both males (p = .0069) and females (p = .0063). Serum cotinine, as a marker for tobacco exposure, is a statistically significant risk factor for decreased BMC in both genders and should be included in multivariate regression models to predict low BMC.

DARPP-32 phosphorylation opposes the behavioral effects of nicotine

BACKGROUND

The addictive properties of nicotine are mediated via dopaminergic pathways and their post-synaptic neurons in the striatum. Because post-synaptic neurons within the striatum contain high levels of the dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32), we hypothesized that DARPP-32 may functionally contribute to the behavioral effects of nicotine.

METHODS

We examined the behavioral effects of nicotine and the phosphorylation state of DARPP-32 in wild-type (WT) and DARPP-32 knockout (KO) mice. In one experiment, we assessed voluntary nicotine intake (0-50 microg/ml) of WT and KO mice in a two-bottle choice paradigm. In a separate experiment, the motor-depressant effects of acute and repeated nicotine injections (0-.8 mg/kg, subcutaneously [SC]) were assessed. The phosphorylation of DARPP-32 at threonine34 and threonine75 were examined using Western blotting.

RESULTS

A heightened responsiveness to nicotine was seen in KO mice when compared with WT mice in oral intake and motor depression. The enhanced responsiveness in KO mice was not due to alterations in taste sensations, fluid intake, or blood nicotine or cotinine levels. Systemic injections of nicotine resulted in increased striatal DARPP-32 phosphorylation at threonine34 and threonine75.

CONCLUSIONS

DARPP-32 opposes the behavioral effects of nicotine possibly via concurrent phosphorylation at the two threonine sites.

Nicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-butanone metabolism by cytochrome P450 2B6

Nicotine is the major addictive agent in tobacco; it is primarily metabolized by 5'-oxidation. 4-(Methylnitrosamine)-1-(3-pyridyl)-1-butanone (NNK), a potent lung carcinogen generated from nicotine during the curing of tobacco, is metabolically activated by P450 enzymes. P450 2A6 is the primary hepatic catalyst of nicotine metabolism and also catalyzes NNK alpha-hydroxylation, albeit less efficiently. It was previously reported that P450 2B6 catalyzed nicotine 5'-oxidation. The studies presented here investigate the relative importance of P450 2B6 as a catalyst of nicotine 5'-oxidation and NNK alpha-hydroxylation by human liver microsomes (HLMs). Radioflow high-performance liquid chromatography analysis and tritiated substrates were used to monitor the products of nicotine and NNK metabolism. The primary product of P450 2B6-catalyzed nicotine metabolism was the delta1'(5') iminium ion. The only other metabolite detected was nornicotine, the product of methyl oxidation, formed at about one-fourth the rate of the delta1' (5') iminium ion. We determined that P450 2B6 was a much less efficient catalyst of nicotine 5'-oxidation than previously reported, with an estimated K(m) of 820 microM. In contrast, the K(m) of NNK alpha-hydroxylation was 33 muM. Experiments with P450 2A6- and P450 2B6-selective inhibitory antibodies did not support P450 2B6 as a significant catalyst of nicotine 5'-oxidation by HLMs, and it is unlikely that this enzyme contributes to nicotine metabolism in smokers who express P450 2A6. However, P450 2B6 contributed significantly to NNK metabolism in HLMs expressing both P450 2B6 and P450 2A6, suggesting a possible role for P450 2B6 in NNK metabolic activation.

[Assessment of behavioral dependence with the Glover-Nilsson test in smoking cessation treatment]

OBJECTIVE

To assess behavioral dependence using the Glover-Nilsson test and determine its association with successful smoking cessation.

MATERIAL AND METHODS

An analytical longitudinal study was carried out, the target population of which consisted of smokers who enrolled in a smoking cessation clinic for treatment. The following variables were examined: age, sex, nicotine dependence (Fagerström test), psychoactive drug use, prior attempts at quitting, and behavioral dependence measured with the Glover-Nilsson test. The most recent version of this test is an 11-item questionnaire which classifies behavioral dependence according to the scores obtained: mild (<12), moderate (12-22), severe (23-33), and very severe (>33). Successful cessation was defined as self-reported abstinence confirmed by measurement of expired CO level (< or =10 ppm). Results were expressed as means (SD) for quantitative variables and percentages and absolute frequencies for qualitative variables.

RESULTS

The study population consisted of 167 smokers--89 men (53.3%) and 78 women (46.7%)--with a mean age of 43.5 (9.9) years, a nicotine dependence score (Fagerström test) of 6.5 (2.2) points, and a Glover-Nilsson score of 23.3 (6.6). Of the study population, 65.9% (n=110) had made previous attempts at quitting. Abstinence at 3 months was 55.1% (n=92). Differences between the sexes were found for age and previous attempts at quitting. Younger patients had higher scores on the Glover-Nilsson test and the Fagerström test and lower abstinence rates.

CONCLUSIONS

Severe behavioral dependence can result in less successful cessation outcome. All aspects related to dependence must be assessed to help select the most adequate pharmacological and psychological treatment for results to be optimized.

Nicotine addiction and comorbidity with alcohol abuse and mental illness

The World Health Organization estimates that one-third of the global adult population smokes. Because tobacco use is on the rise in developing countries, death resulting from tobacco use continues to rise. Nicotine, the main addictive component of tobacco, initiates synaptic and cellular changes that underlie the motivational and behavioral alterations that culminate in addiction. Nicotine addiction progresses rapidly in adolescents and is most highly expressed in vulnerable people who have psychiatric illness or other substance abuse problems.

Methylphenidate increases cigarette smoking

RATIONALE

Methylphenidate (Ritalin) and d-amphetamine (Dexedrine), stimulants commonly prescribed for behavioral problems associated with attention deficit hyperactivity disorder (ADHD), produce a similar constellation of behavioral effects. The results of previous studies suggest that d-amphetamine increases rates of smoking and the reinforcing effects of smoking. The effects of methylphenidate on smoking have not been assessed although it is the most commonly prescribed pharmacotherapy for ADHD and individuals with ADHD are at increased risk for smoking.

OBJECTIVE

In this experiment the acute effects of a range of doses of methylphenidate (5, 10, 20, and 40 mg) and placebo were assessed in ten cigarette smokers who were not attempting to quit and were without ADHD or other Axis I psychiatric disorders.

METHODS

Each dose of methylphenidate was tested once, whereas placebo was tested twice. One hour after ingesting drug, participants were allowed to smoke ad libitum for 4 h. Measures of smoking included total cigarettes smoked, total puffs, latency to the first cigarette, and carbon monoxide levels. Snacks and decaffeinated drinks were available ad libitum, and caloric intake during the 4-h smoking session was calculated.

RESULTS

Methylphenidate dose dependently increased the total number of cigarettes smoked, number of puffs, and carbon monoxide levels. As expected, methylphenidate dose dependently decreased the number of food items consumed and caloric intake.

CONCLUSIONS

The results of this experiment suggest that methylphenidate, like d-amphetamine, increases rates of cigarette smoking.

Ventral striatum/nucleus accumbens activation to smoking-related pictorial cues in smokers and nonsmokers: a functional magnetic resonance imaging study

BACKGROUND

Converging evidence from several theories of the development of incentive-sensitization to smoking-related environmental stimuli suggests that the ventral striatum plays an important role in the processing of smoking-related cue reactivity.

METHODS

Twenty-six healthy right-handed volunteers (14 smokers and 12 nonsmoking controls) underwent functional magnetic resonance imaging (fMRI) during which neutral and smoking-related images were presented. Region of interest analyses were performed within the ventral striatum/nucleus accumbens (VS/NAc) for the contrast between smoking-related (SR) and nonsmoking related neutral (N) cues.

RESULTS

Group activation for SR versus N cues was observed in smokers but not in nonsmokers in medial orbitofrontal cortex, superior frontal gyrus, anterior cingulate cortex, and posterior fusiform gyrus using whole-brain corrected Z thresholds and in the ventral VS/NAc using uncorrected Z-statistics (smokers Z = 3.2). Region of interest analysis of signal change within ventral VS/NAc demonstrated significantly greater activation to SR versus N cues in smokers than controls.

CONCLUSIONS

This is the first demonstration of greater VS/NAc activation in addicted smokers than nonsmokers presented with smoking-related cues using fMRI. Smokers, but not controls, demonstrated activation to SR versus N cues in a distributed reward signaling network consistent with cue reactivity studies of other drugs of abuse.

Smoking cessation in patients with coronary artery disease

BACKGROUND

Smoking cessation is an important factor in the primary and secondary prevention of cardiac events. Although multiple clinical trials have examined the efficacy of various smoking cessation aids, a systematic review of the efficacy and safety of smoking cessation aids has not been done.

METHODS

This paper reviews the effects of smoking on coronary artery disease. In addition, we identify randomized controlled trials examining the efficacy and safety of smoking cessation aids from the years 1970 to 2004. We then pooled the trial results for 6- and 12-month rates of continuous smoking abstinence.

RESULTS

The 4 principal mechanisms of cardiovascular damage caused by cigarette smoking are induction of a hypercoagulable state, reduction of oxygen delivery because of carbon monoxide, coronary vasoconstriction, and nicotine-induced hemodynamic effects. Our review of clinical trials suggests that each smoking cessation aid improved continuous smoking abstinence rates at both 6 and 12 months compared with placebo. The 12-month abstinence rates for the active versus placebo treatments were the following: nicotine patch 11.1% versus 5.5%, nicotine gum 27.3% versus 16.5%, nicotine inhaler 16.9% versus 9.1%, bupropion 18.5% versus 6.6%, and behavioral therapy 20.0% versus 13.9%.

CONCLUSIONS

Several smoking-related mechanisms are responsible for the development of atherosclerosis and the induction of cardiac events. Smoking cessation aids effect a modest increase in smoking abstinence at 12 months compared with placebo. In spite the apparent success of cessation aids, smoking relapse rates are quite high.

Nicotine addiction through a neurogenomic prism: ethics, public health, and smoking

Studies are under way to examine the neurogenetic factors contributing to smoking behaviors. The combined approaches of genomics, molecular biology, neuroscience, and pharmacology are expected to fuel developments in pharmacogenetics, to create new genetic tests, and ultimately to provide the basis for innovative strategies for smoking cessation and prevention. The emergence of a neurogenomic understanding of nicotine addiction is likely to induce fundamental changes in popular, clinical, and public health views of smoking, which could significantly shape existing practices and policies to reduce tobacco use. Still a nascent area of research, nicotine addiction provides an excellent case study through which to anticipate key ethical and policy issues in both behavioral genetics and the neurogenomics of addictive behaviors.

Metabolism and disposition kinetics of nicotine

Nicotine is of importance as the addictive chemical in tobacco, pharmacotherapy for smoking cessation, a potential medication for several diseases, and a useful probe drug for phenotyping cytochrome P450 2A6 (CYP2A6). We review current knowledge about the metabolism and disposition kinetics of nicotine, some other naturally occurring tobacco alkaloids, and nicotine analogs that are under development as potential therapeutic agents. The focus is on studies in humans, but animal data are mentioned when relevant to the interpretation of human data. The pathways of nicotine metabolism are described in detail. Absorption, distribution, metabolism, and excretion of nicotine and related compounds are reviewed. Enzymes involved in nicotine metabolism including cytochrome P450 enzymes, aldehyde oxidase, flavin-containing monooxygenase 3, amine N-methyltransferase, and UDP-glucuronosyltransferases are represented, as well as factors affecting metabolism, such as genetic variations in metabolic enzymes, effects of diet, age, gender, pregnancy, liver and kidney diseases, and racial and ethnic differences. Also effects of smoking and various inhibitors and inducers, including oral contraceptives, on nicotine metabolism are discussed. Due to the significance of the CYP2A6 enzyme in nicotine clearance, special emphasis is given to the effects and population distributions of CYP2A6 alleles and the regulation of CYP2A6 enzyme.

Personal factors influencing Korean American men's smoking behavior: addiction, health, and age

The purpose of this qualitative study was to identify factors influencing Korean American men's smoking behavior. Focus-group research method was used, and participants were 22 Korean male smokers in New York City. They talked about their experiences of smoking and smoking cessation. Addiction, health, and age emerged as major personal factors affecting Korean men's smoking behavior. Their experiences in relation to addiction were similar to those reported in other racial/ethnic groups, whereas the dramatic change in the perception of smoking-related health risks coming with their forties, some cessation strategies used by former smokers, and preference for group meetings over individual counseling appeared to be specific to Korean men.

Cigarette smoking and nicotine dependence

Tobacco use is the single most preventable cause of death, disability, and disease in the United States and is projected to be the leading cause of death and disability across all developed countries by the year 2020. Understanding nicotine dependence, its causes, consequences, and effective treatments is critical to the nation's public health agenda. This article presents a brief overview of nicotine dependence with particular emphasis placed on understanding what nicotine dependence is, why it occurs, how it is measured, and how it can be managed through effective treatments.

Cigarette smoking: Evidence to guide measurement

Smoking cessation programs measure outcomes in terms of abstinence from or reduction in smoking. These outcomes can be measured through self-report by the smoker, through measurement with a biological marker of smoking, or through a combination of both. Consideration of the relative advantages of self-report and biomarker approaches is important in the selection of measurement strategies to evaluate outcomes in smoking cessation interventions. In this article both ways of measuring smoking behavior, self-report and biomarkers of carbon monoxide, cotinine, nicotine, thiocyanate, and alkaloids of nicotine, are explored. Measurement approaches are discussed in light of research evidence and their physiologic bases.

MAO-B knockout mice exhibit deficient habituation of locomotor activity but normal nicotine intake

Low levels of monoamine oxidase-B (MAO-B) activity, such as those observed in smokers, are also associated with behavioral traits such as a heightened responsiveness to novelty. However, the exact mechanism by which low MAO-B activity influences smoking and heightened responsiveness to novelty is still poorly understood. We used MAO-B knockout (KO) mice to test the hypothesis that MAO-B concomitantly affects locomotor responses in a novel inescapable open field and nicotine intake. Male wild-type (WT) and MAO-B KO mice were placed in an inescapable open field and their horizontal locomotor activity was measured for 30 min per day for 5 days. MAO-B KO mice exhibited impaired within-session habituation of locomotor activity, as compared to WT mice. Separate groups of male WT and MAO-B KO mice were individually housed in their home cages with two water bottles. One of the bottles contained tap water and the other contained nicotine (0, 3.125, 6.25, 12.5, 25, 50 or 100 micro g/ml). The total amount of water and nicotine solution consumed was measured every three days for 16 days. MAO-B KO mice and WT mice consumed equal amounts of nicotine and exhibited comparable concentration-dependent nicotine preference and aversion over a period of 16 days. The data suggest that the absence of MAO-B impairs the ability of mice to habituate in the inescapable environment, but does not alter their nicotine intake.

Substance abuse and pharmacy practice: what the community pharmacist needs to know about drug abuse and dependence

Pharmacists, the most accessible of health care professionals, are well positioned to help prevent and treat substance use disorders and should prepare themselves to perform these functions. New research improves our knowledge about the pharmacological and behavioral risks of drug abuse, supports the clinical impression that drug dependence is associated with long-lasting neurochemical changes, and demonstrates effective pharmacological treatments for certain kinds of drug dependencies. The profession is evolving. Pharmacists are engaging in new practice behaviors such as helping patients manage their disease states. Collaborative practice agreements and new federal policies set the stage for pharmacists to assist in the clinical management of opioid and other drug dependencies. Pharmacists need to be well informed about issues related to addiction and prepared not only to screen, assess, and refer individual cases and to collaborate with physicians caring for chemically dependent patients, but also to be agents of change in their communities in the fight against drug abuse.At the end of this article the pharmacist will be better able to:1. Explain the disease concept of chemical dependence2. Gather the information necessary to conduct a screen for chemical dependence3. Inform patients about the treatment options for chemical dependence4. Locate resources needed to answer questions about the effects of common drugs of abuse (alcohol, marijuana, narcotics, "ecstasy", and cocaine)5. Develop a list of local resources for drug abuse treatment6. Counsel parents who are concerned about drug use by their children7. Counsel individuals who are concerned about drug use by a loved one.8. Counsel individuals who are concerned about their own drug use

Tobacco use and dependence

OBJECTIVES

To review tobacco use and dependence including nicotine pharmacology and addiction, and pharmacologic treatment.

DATA SOURCES

Professional journals, books, government publications.

CONCLUSION

Smoking is addictive and a major health problem. Habitual nicotine use is central to sustaining smoking dependence. This article provides the necessary basis for understanding nicotine addiction and pharmacologic therapies.

IMPLICATIONS FOR NURSING PRACTICE

Nurses' knowledge about nicotine addiction is important in helping patients to quit smoking.

Rat hepatic CYP2E1 is induced by very low nicotine doses: an investigation of induction, time course, dose response, and mechanism

CYP2E1 is an ethanol- and drug-metabolizing enzyme that can also activate procarcinogens and hepatotoxicants and generate reactive oxygen species; it has been implicated in the pathogenesis of liver diseases and cancer. Cigarette smoke increases CYP2E1 activity in rodents and in humans and we have shown that nicotine (0.1-1.0 mg/kg s.c. x 7 days) increases CYP2E1 protein and activity in the rat liver. In the current study, we have shown that the induction peaks at 4 h postnicotine (1 mg/kg s.c. x 7 days) treatment and recovers within 24 h. No induction was observed after a single injection, and 18 days of treatment did not increase the levels beyond that found at 7 days. We found that CYP2E1 is induced by very low doses of chronic (x 7 days) nicotine with an ED50 value of 0.01 mg/kg s.c.; 0.01 mg/kg in a rat model results in peak cotinine levels (nicotine metabolite) similar to those found in people exposed to environmental tobacco smoke (passive smokers; 2-7 ng/ml). Previously, we have shown no change in CYP2E1 mRNA, and our current mechanistic study indicates that nicotine does not regulate CYP2E1 expression by protein stabilization. We postulated that a nicotine metabolite could be causing the induction but found that cotinine (1 mg/kg x 7 days) did not increase CYP2E1. Our findings indicate that nicotine increases CYP2E1 at very low doses and may enhance CYP2E1-related toxicity in smokers, passive smokers, and people treated with nicotine (e.g., smokers, patients with Alzheimer's disease, ulcerative colitis or Parkinson's disease).

Smoking, stress, and negative affect: correlation, causation, and context across stages of smoking

This transdisciplinary review of the literature addresses the questions, Do stress and negative affect (NA) promote smoking? and Does smoking genuinely relieve stress and NA? Drawing on both human and animal literatures, the authors examine these questions across three developmental stages of smoking--initiation, maintenance, and relapse. Methodological and conceptual distinctions relating to within- and between-subjects levels of analyses are emphasized throughout the review. Potential mechanisms underlying links between stress and NA and smoking are also reviewed. Relative to direct-effect explanations, the authors argue that contextual mediator-moderator approaches hold greater potential for elucidating complex associations between NA and stress and smoking. The authors conclude with recommendations for research initiatives that draw on more sophisticated theories and methodologies.

Is there a role for assessment in smoking cessation treatment?

Recent strides have been made in smoking cessation as a number of behavioral and pharmacological treatments have proven effective. These treatments are briefly reviewed. The role of assessment in the treatment process, however, is less clear. Indeed, to date, there are few data suggesting that specialized assessment can be used to guide prescriptive treatment. As such, the question becomes one of how, or whether, assessment should be used in smoking cessation. We address these questions and argue that despite the dearth of empirical substantiation, certain aspects of smoking behavior should be assessed in that they: (1) help identify behavioral, physiological, and psychological conditions that maintain smoking, (2) help describe the problem (smoking) with enough clarity to foster both clinical understanding and diagnosis, and (3) offer prediction and evaluation of treatment process and outcome. Promising assessment-based treatments are also discussed, as well as recommendations for future directions pertaining to the role of assessment in smoking cessation.

Chemical profile of two types of oral snuff tobacco

The chemical-analytical profile of two US brands of oral moist snuff was determined. These two brands were bought in five geographical locations (NY, MA, CO, CA and KY in the US). They were mixed thoroughly to yield representative samples. Brand A had a pH of 5.84 and nicotine content of 0.42%, while brand B had a pH of 7.99 and nicotine content of 2.73%. At pH 5.84, only 1% of the nicotine is present as a free base while 59% of nicotine is present in unprotonated form at pH 7.99. It is the unprotonated form of nicotine that is most readily absorbed through the mucous membrane in the oral cavity. Snuff A contained also significantly lower levels of moisture, nitrate, nitrite and tobacco-specific nitrosamines than snuff B. The University of Kentucky reference snuff 1S3 was analyzed as an external control sample. These two snuff brands are currently being assayed with rats in a short-term and in long-term bioassays to test the concept that the tobacco-specific N-nitrosamines are major contributors to the carcinogenic activity of oral snuff.

The epidemiology of smoking: health consequences and benefits of cessation

Tobacco use is the single most important preventable health risk in the developed world, and an important cause of premature death worldwide. Smoking causes a wide range of diseases, including many types of cancer, chronic obstructive pulmonary disease, coronary heart disease, stroke, peripheral vascular disease, and peptic ulcer disease. In addition, smoking during pregnancy adversely affects fetal and neonatal growth and development. Recent decades have seen a massive expansion in tobacco use in the developing world and accelerating growth in smoking among women in the developed world. Globally, smoking-related mortality is set to rise from 3 million annually (1995 estimate) to 10 million annually by 2030, with 70% of these deaths occurring in developing countries. Many of the adverse health effects of smoking are reversible, and smoking cessation treatments represent some of the most cost effective of all healthcare interventions. Although the greatest benefit accrues from ceasing smoking when young, even quitting in middle age avoids much of the excess healthcare risk associated with smoking. In order to improve smoking cessation rates, effective behavioural and pharmacological treatments, coupled with professional counselling and advice, are required. Since smoking duration is the principal risk factor for smoking-related morbidity, the treatment goal should be early cessation and prevention of relapse.

Effects of nicotine on alcohol intake in a rat model of depression

Clinical studies suggest that depression facilitates alcohol abuse. Depressed individuals also have increased rates of smoking, and it has been suggested that nicotine may improve depression. It is therefore possible that nicotine may reduce alcohol use in depression. To investigate this potential relationship, we evaluated alcohol intake in an animal model of depression, which consists of administering clomipramine (CLI), a preferential serotonin reuptake inhibitor, to neonatal rats. This pharmacological manipulation produces adult depression-like behaviors, such as reduced aggressiveness, decreased pleasure seeking, diminished sexual activity, increased locomotor activity and increased REM sleep. In this study, we found that CLI rats exhibited significantly higher locomotor activity, lower aggressiveness and higher alcohol intake than control rats. Chronic administration of a low dose of nicotine (0.25 mg/kg/day) or a sham operation did not modify these behaviors. However, chronic administration of nicotine at a higher dose (1.5 mg/kg/day) significantly increased aggressive behavior and reduced alcohol intake in CLI rats. The effect of nicotine on alcohol intake lasted at least 1 month after cessation of nicotine administration. These results indicate that nicotine reverted some depression signs and reduced alcohol self-administration in the CLI model of depression.