Slower metabolism and reduced intake of nicotine from cigarette smoking in Chinese-Americans

Light and intermittent smoking among California's Asian Americans

INTRODUCTION

Asian Americans, along with other ethnic minorities, have been described to be more likely than Whites to be light and intermittent smokers. Characterizing Asian American smoking behavior accurately on a population level requires oversampling groups of different national origin and including non-English-speaking participants.

METHODS

We analyzed the California Health Interview Survey to compare moderate/heavy (> or =10 cigarettes/day), light (0-9 cigarettes/day), and intermittent (not daily) smoking patterns in Asian Americans with those of Whites. We also examined whether social and demographic factors that had been associated with Asian American smoking prevalence also were associated with light and intermittent smoking patterns in each of the national origin groups.

RESULTS

Most Asian American smokers were more likely to be light and intermittent smokers (range = 36.6%-61.5% for men and 29.9%-81.5% for women) compared with Whites, with lower mean cigarette consumption. Asian American light and intermittent smokers were more likely than moderate/heavy smokers to be women (odds ratio [OR] = 2.12, 95% CI = 1.14-3.94), highly educated (OR = 3.16, 95% CI = 1.21-8.28), not Korean (compared with Chinese; OR = 0.32, 95% CI = 0.13-0.79), and bilingual speakers with high English language proficiency compared with English-only speakers (OR = 2.83, 95% CI = 1.21-6.84). Asian American intermittent smokers were more likely than daily smokers to be women (OR = 2.25, 95% CI = 1.08-4.72) and to have lower household income.

DISCUSSION

The predominance of Asian American light and intermittent smoking patterns has important implications for developing effective tobacco control outreach. Further studies are needed to elaborate the relationship between biological, psychosocial, and cultural factors influencing Asian American smoking intensity.

Optimal serum cotinine levels for distinguishing cigarette smokers and nonsmokers within different racial/ethnic groups in the United States between 1999 and 2004

Cotinine, a metabolite of nicotine, is widely used to distinguish smokers from nonsmokers in epidemiologic studies and smoking-cessation clinical trials. As the magnitude of secondhand smoke exposure declines because of proportionally fewer smokers and more clean-indoor-air regulations, the optimal cotinine cutpoint with which to distinguish smokers from nonsmokers is expected to change. The authors analyzed data on 3,078 smokers and 13,078 nonsmokers from the National Health and Nutrition Examination Survey for 1999-2004. Optimal serum cotinine concentrations for discriminating smokers from nonsmokers were determined using receiver operator characteristic curve analysis. Optimal cotinine cutpoints were 3.08 ng/mL (sensitivity = 96.3%, specificity = 97.4%) and 2.99 ng/mL (sensitivity = 86.5%, specificity = 93.1%) for adults and adolescents, respectively. Among adults, optimal cutpoints differed by race/ethnicity: They were 5.92 ng/mL, 4.85 ng/mL, and 0.84 ng/mL for non-Hispanic blacks, non-Hispanic whites, and Mexican Americans, respectively. Among adolescents, cutpoints were 2.77 ng/mL, 2.95 ng/mL, and 1.18 ng/mL for non-Hispanic blacks, non-Hispanic whites, and Mexican Americans, respectively. Use of the currently accepted cutpoint of 14 ng/mL overestimates the number of nonsmokers in comparison with the proposed new overall cutpoint of 3 ng/mL or the race/ethnicity-specific cutpoints of 1-6 ng/mL.

Nicotine chemistry, metabolism, kinetics and biomarkers

Nicotine underlies tobacco addiction, influences tobacco use patterns, and is used as a pharmacological aid to smoking cessation. The absorption, distribution and disposition characteristics of nicotine from tobacco and medicinal products are reviewed. Nicotine is metabolized primarily by the liver enzymes CYP2A6, UDPglucuronosyltransferase (UGT), and flavin-containing monooxygenase (FMO). In addition to genetic factors, nicotine metabolism is influenced by diet and meals, age, sex, use of estrogen-containing hormone preparations, pregnancy and kidney disease, other medications, and smoking itself. Substantial racial/ethnic differences are observed in nicotine metabolism, which are likely influenced by both genetic and environmental factors. The most widely used biomarker of nicotine intake is cotinine, which may be measured in blood, urine, saliva, hair, or nails. The current optimal plasma cotinine cut-point to distinguish smokers from non-smokers in the general US population is 3 ng ml(-1). This cut-point is much lower than that established 20 years ago, reflecting less secondhand smoke exposure due to clear air policies and more light or occasional smoking.

Role of xenobiotic metabolic enzymes in cancer epidemiology

The cause of the majority of cancers is poorly understood albeit multifactorial. The ultimate consequence of etiological factors where defined is an alteration within the cellular genotype, which is manifested in the cells acquiring malignant phenotype. There are several environmental carcinogens that contribute to carcinogenesis. These carcinogens are metabolized by a large number of enzymes, including the cyto-chrome P 450 group, glutathione-S-transferase (GST), the uridine glucuronyl transferase (UGT) super-family, alcohol-metabolizing enzymes, sulphatases, etc. These enzymes can either inactivate carcinogens or in some cases generate reactive moieties that lead to carcinogenesis. This review summarises the available evidence regarding the role of xenobiotic metabolic enzymes and their role in cancer epidemiology. The available data and studies have identified correlates between expression of various metabolizing enzymes with risk of malignancies known to be induced by their substrates. The data may have relevance in one population but not for another for a specific malignancy and at times may be conflicting. We believe that with mature data in the future it may be possible to stratify patients by risk.

Teaching 'race' at medical school: social scientists on the margin

This essay examines the efforts of social scientists and humanities scholars to teach students at a major US medical school about 'race'. The objectives were to explain that race is no longer considered a biologically legitimate concept and to demonstrate that race remains an influential social classification, causing social and biological harm. That is, these educators sought to reframe the medical significance of race. An examination of the email discussions of those involved in this teaching exercise (which included the author) reveals concerns over the credibility of social scientists and humanities scholars speaking on genetics in the modern medical school. It also indicates the intellectual and curricular marginalization of critiques of racial classification in medical education. In science studies journals one can read convincing deconstructions of the new genetics of race, but it is rare to find an analysis of how ideas about race figure in the mundane practice of educating future medical doctors and researchers. Through examination of an exemplary, wide-ranging discussion of an attempt to teach on race in the medical curriculum, this essay addresses the disciplinary and institutional difficulties of translating critiques of controversial science into pedagogy.

Clinical pharmacology of nicotine: implications for understanding, preventing, and treating tobacco addiction

Understanding the basic and clinical pharmacology of nicotine provides a basis for improved prevention and treatment of tobacco addiction. Nicotine acts on nicotinic cholinergic receptors in the brain to release dopamine and other neurotransmitters that sustain addiction. Neuroadaptation and tolerance involve changes in both nicotinic receptors and neural plasticity. Nicotine addiction can occur in the context of physical dependence characterized by self-medication to modulate negative affect and/or to relieve withdrawal symptoms, as well as, in light or occasional smokers, primarily for positive reinforcement in specific situations. Nicotine is metabolized primarily by CYP2A6. Its clearance exhibits considerable individual variability that is determined by genetic, racial, and hormonal (sex) factors. Genetically slow metabolism of nicotine appears to be associated with a lower level of dependence. Nicotine dependence is highly heritable and appears to be influenced by genes coding for some nicotine receptor subtypes, some neurotransmitter genes, and genes involved in neural connectivity. Novel pharmacotherapies for nicotine dependence include partial agonists for nicotinic receptors and nicotine vaccines. Pharmacogenetic studies suggest various candidate genes and a nicotine metabolism phenotype that influence outcome. Human pharmacology studies of nicotine and smoking behavior also provide a basis for assessing the benefits and risks of long-term nicotine use for harm reduction and for a potential cigarette regulatory strategy that includes reducing nicotine content of cigarettes to nonaddictive levels.

Tobacco smoking and cancer: a meta-analysis

We conducted a systematic meta-analysis of observational studies on cigarette smoking and cancer from 1961 to 2003. The aim was to quantify the risk for 13 cancer sites, recognized to be related to tobacco smoking by the International Agency for Research on Cancer (IARC), and to analyze the risk variation for each site in a systematic manner. We extracted data from 254 reports published between 1961 and 2003 (177 case-control studies, 75 cohorts and 2 nested case-control studies) included in the 2004 IARC Monograph on Tobacco Smoke and Involuntary Smoking. The analyses were carried out on 216 studies with reported estimates for 'current' and/or 'former' smokers. We performed sensitivity analysis, and looked for publication and other types of bias. Lung (RR = 8.96; 95% CI: 6.73-12.11), laryngeal (RR = 6.98; 95% CI: 3.14-15.52) and pharyngeal (RR = 6.76; 95% CI: 2.86-15.98) cancers presented the highest relative risks (RRs) for current smokers, followed by upper digestive tract (RR = 3.57; 95% CI: 2.63-4.84) and oral (RR = 3.43; 95% CI: 2.37-4.94) cancers. As expected, pooled RRs for respiratory cancers were greater than the pooled estimates for other sites. The analysis of heterogeneity showed that study type, gender and adjustment for confounding factors significantly influence the RRs estimates and the reliability of the studies.

Determinants of salivary cotinine level: a population-based study in Brazil

OBJECTIVE: A cross-sectional population-based study was conducted to assess, in active smokers, the relationship of number of cigarettes smoked and other characteristics to salivary cotinine concentrations. METHODS: A random sample of active smokers aged 15 years or older was selected using a stepwise cluster sample strategy, in the year 2000 in Rio de Janeiro, Brazil. The study included 401 subjects. Salivary cotinine concentration was determined using gas chromatography with nitrogen-phosphorus detection. A standard questionnaire was used to collect demographic and smoking behavioral data. The relation between the number of cigarettes smoked in the last 24h and cotinine level was examined by means of a nonparametric fitting technique of robust locally weighted regression. RESULTS: Significantly (p<0.05) higher adjusted mean cotinine levels were found in subjects smoking their first cigarette within five minutes after waking up, and in those smoking 1-20 cigarettes in the last 24h who reported inhaling more than ½ the time. In those smoking 1-20 cigarettes, the slope was significantly higher for those subjects waiting for more than five minutes before smoking their first cigarette after waking up, and those smoking "light" cigarettes when compared with their counterparts. These heterogeneities became negligible and non-significant when subjects with cotinine >40 ng/mL per cigarette were excluded. CONCLUSIONS: There was found a positive association between self-reporting smoking five minutes after waking up, and inhaling more than ½ the time are consistent and higher cotinine levels. These can be markers of dependence and higher nicotine intake. Salivary cotinine proved to be a useful biomarker of recent smoking and can be used in epidemiological studies and smoking cessation programs.

Effects of pregnancy on nicotine self-administration and nicotine pharmacokinetics in rats

RATIONALE

Because of the adverse effects of smoking during pregnancy, understanding the factors that influence maternal smoking may help in developing better treatments to help women quit smoking during pregnancy. Animal models could be useful for this purpose.

OBJECTIVE

The purpose of the present study was to begin the development of an animal model of smoking during pregnancy by initially characterizing nicotine self-administration (NSA) in pregnant rats. Another purpose was to begin to explore the effects of pregnancy on nicotine pharmacokinetics in rats.

MATERIALS AND METHODS

In experiment 1, female rats self-administering nicotine during 23-h sessions were examined throughout gestation and lactation. In experiment 2, locomotor activity was measured during pregnancy to assess further potential motor effects of pregnancy. Experiments 3 and 4 compared the single-dose pharmacokinetics of nicotine in male, nonpregnant female, and pregnant females in the first and third trimester of pregnancy and the first week of lactation.

RESULTS

NSA decreased over the course of pregnancy with NSA significantly lower in the third trimester compared to nonpregnant controls. NSA remained suppressed for up to 10 days into lactation. Locomotor behavior was also significantly suppressed during the second and third trimesters and throughout lactation. Nicotine elimination was slower in pregnant females compared to nonpregnant females only in the third trimester.

CONCLUSIONS

NSA, locomotor behavior, and nicotine elimination in rats are decreased during late pregnancy. The present study is the first to characterize NSA during pregnancy in animals, providing a potential model of maternal smoking in humans.

Most Latino smokers in California are low-frequency smokers

AIMS

We examine the phenomenon of low-frequency smoking (non-daily smoking or smoking </= 5 cigarettes daily) among California Latinos and address its implications for addiction theory and population tobacco control.

DESIGN, SETTING AND PARTICIPANTS

Data gathered in 2001 and 2003 through the California Health Interview Survey (CHIS), the largest general health survey in California. The present study focused on Latino current smokers (n = 1254 for CHIS 2001; n = 946 for CHIS 2003).

MEASUREMENT

Latino smokers reporting either non-daily smoking or smoking </=5 cigarettes daily were identified and grouped into one category: low-frequency smokers.

FINDINGS

Weighted by population parameters, more than 70% of Latino smokers in California were found to be low-frequency smokers [70.7% (CI = 67.2%, 73.9%) in 2001 and 70.8% (CI = 67.1%-74.2%) in 2003]. This high proportion cut across all demographic dimensions in both surveys, suggesting pervasiveness and reliability of this phenomenon. Proportions for non-daily smokers and low-rate daily smokers were 48.6% and 22.1% in 2001 and 54.9% and 15.9% in 2003. In both surveys, more than 80% of non-daily smokers consumed </= 5 cigarettes on their smoking days.

CONCLUSIONS

The fact that most Latino smokers are low-frequency smokers calls for a new theoretical framework--beyond withdrawal-based theories--to account for the prevalence of this behavior on the population level. It also calls into question the harm-reduction approach as a tobacco control strategy for California Latino populations. Strategies emphasizing that every cigarette can hurt, and encouraging complete cessation, seem more fitting for this group of smokers.

Genetic variability in CYP2A6 and the pharmacokinetics of nicotine

Nicotine is the psychoactive substance responsible for tobacco dependence. It is also a therapeutic used to aid smoking cessation. Cytochrome P450 (CYP)2A6 is the human hepatic enzyme that mediates most of nicotine’s metabolic inactivation to cotinine. Genetic variation in the CYP2A6 gene can increase or decrease enzyme activity through altering the protein’s expression level or its structure and function. This article reviews CYP2A6 genetic variation and its impact on in vivo nicotine kinetics, including a description of the individual variants, different phenotyping approaches for assessing in vivo CYP2A6 activity and other sources of variation in nicotine metabolism such as gender. In addition, the effect of CYP2A6 polymorphisms on smoking behavior and tobacco-related lung cancer risk are briefly described. Furthering knowledge in this area will improve interpretation of studies examining smoking behavior, as well as those using nicotine as a therapeutic agent.

Identifying health disparities across the tobacco continuum

AIMS

Few frameworks have addressed work-force diversity, inequities and inequalities as part of a comprehensive approach to eliminating tobacco-related health disparities. This paper summarizes the literature and describes the known disparities that exist along the tobacco disease continuum for minority racial and ethnic groups, those living in poverty, those with low education and blue-collar and service workers. The paper also discusses how work-force diversity, inequities in research practice and knowledge allocation and inequalities in access to and quality of health care are fundamental to addressing disparities in health.

METHODS

We examined the available scientific literature and existing public health reports to identify disparities across the tobacco disease continuum by minority racial/ethnic group, poverty status, education level and occupation.

FINDINGS

Results indicate that differences in risk indicators along the tobacco disease continuum do not explain fully tobacco-related cancer consequences among some minority racial/ethnic groups, particularly among the aggregate groups, blacks/African Americans and American Indians/Alaska Natives. The lack of within-race/ethnic group data and its interactions with socio-economic factors across the life-span contribute to the inconsistency we observe in the disease causal paradigm.

CONCLUSIONS

More comprehensive models are needed to understand the relationships among disparities, social context, diversity, inequalities and inequities. A systematic approach will also help researchers, practitioners, advocates and policy makers determine critical points for interventions, the types of studies and programs needed and integrative approaches needed to eliminate tobacco-related disparities.

Nicotine metabolism and CYP2A6 activity in a population of black African descent: impact of gender and light smoking

Genetic variation in CYP2A6 (the main nicotine metabolizing enzyme) accounts for some, but not all, of the interindividual and interethnic variability in the rates of nicotine metabolism. We conducted a nicotine kinetic study in smokers and nonsmokers of black African descent (N=190), excluding those with common genetic variants in CYP2A6, to investigate the association of demographic variables with CYP2A6 activity (3HC/COT ratio) and nicotine disposition kinetics (estimated nicotine AUC). An additional aim was to examine whether impaired CYP2A6 activity and/or nicotine disposition kinetics were associated with lower cigarette consumption in a population of light smokers (mean<or=10 cigarettes per day). We found that smokers had decreased nicotine metabolism (p<0.05), that women had higher CYP2A6 activity (p<0.01) and that, in non-elderly adults, age did not impact CYP2A6 activity (p=0.65) or nicotine disposition kinetics (p=0.06). Our study also demonstrated that neither current alcohol use nor current marijuana use was associated with altered CYP2A6 activity (p=0.55 and 0.72, respectively) or nicotine disposition kinetics (p=0.38 and 0.91, respectively). Despite the light cigarette consumption of the smokers (N=94), higher CYP2A6 activity was associated with greater cigarette consumption (p<0.005). These findings highlight the need for smoking status and gender to be considered when interpreting studies using nicotine.

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.

The role of air nicotine in explaining racial differences in cotinine among tobacco-exposed children

OBJECTIVE

African-American children have higher rates of tobacco-associated morbidity. Few studies have objectively measured racial differences in the exposure of children to tobacco smoke. The objective of this study was to test whether African-American children have higher levels of cotinine compared to white children while accounting for ambient measures of tobacco smoke.

SETTING

Community-based sample of asthmatic children (n = 220) enrolled in an environmental tobacco smoke (ETS) reduction trial.

PARTICIPANTS

A biracial sample (55% African American) of children with asthma aged 5 to 12 years who were routinely exposed to ETS.

MEASUREMENTS

We measured cotinine levels in serum and hair samples at baseline, 6 months, and 12 months. We measured the level of ETS exposure over a 6-month period by placing air nicotine dosimeters in the homes of the children at baseline and at 6-month study visits.

RESULTS

African-American children had significantly higher levels of cotinine at all time points in the study. At the 12-month visit, African-American children had higher levels of serum cotinine (1.39 mug/dL vs 0.80 mug/dL, p = 0.001) and hair cotinine (0.28 ng/mg vs 0.08 ng/mg, p < 0.0001) when compared with white children. In a repeated-measures analysis, African-American children had significantly higher levels of serum cotinine (beta = 0.28, p = 0.04) and hair cotinine (beta = 1.40, p < 0.0001) compared with white children. Air nicotine levels and housing volume were independently associated with higher levels of cotinine.

CONCLUSIONS

Among children with asthma, African-American children have higher levels of serum and hair cotinine compared with white children.

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.

Validity of Expired Carbon Monoxide and Urine Cotinine Using Dipstick Method to Assess Smoking Status

OBJECTIVES

We investigated the validity of the dipstick method (Mossman Associates Inc. USA) and the expired CO method to distinguish between smokers and nonsmokers. We also elucidated the related factors of the two methods.

METHODS

This study included 244 smokers and 50 ex-smokers, recruited from smoking cessation clinics at 4 local public health centers, who had quit for over 4 weeks. We calculated the sensitivity, specificity and Kappa coefficient of each method for validity. We obtained ROC curve, predictive value and agreement to determine the cutoff of expired air CO method. Finally, we elucidated the related factors and compared their effect powers using the standardized regression coefficient.

RESULTS

The dipstick method showed a sensitivity of 92.6%, specificity of 96.0% and Kappa coefficient of 0.79. The best cutoff value to distinguish smokers was 5-6 ppm. At 5 ppm, the expired CO method showed a sensitivity of 94.3%, specificity of 82.0% and Kappa coefficient of 0.73. And at 6 ppm, sensitivity, specificity and Kappa coefficient were 88.5%, 86.0% and 0.64, respectively. Therefore, the dipstick method had higher sensitivity and specificity than the expired CO method. The dipstick and expired CO methods were significantly increased with increasing smoking amount. With longer time since the last smoking, expired CO showed a rapid decrease after 4 hours, whereas the dipstick method showed relatively stable levels for more than 4 hours.

CONCLUSIONS

The dipstick and expired CO methods were both good indicators for assessing smoking status. However, the former showed higher sensitivity and specificity and stable levels over longer hours after smoking, compared to the expired CO method.

A comparison of nicotine dose estimates in smokers between filter analysis, salivary cotinine, and urinary excretion of nicotine metabolites

RATIONALE

Nicotine uptake during smoking was estimated by either analyzing the metabolites of nicotine in various body fluids or by analyzing filters from smoked cigarettes. However, no comparison of the filter analysis method with body fluid analysis methods has been published.

OBJECTIVES

Correlate nicotine uptake estimates between filter analysis, salivary cotinine, and urinary excretion of selected nicotine metabolites to determine the suitability of these methods in estimating nicotine absorption in smokers of filtered cigarettes.

MATERIALS AND METHODS

A 5-day clinical study was conducted with 74 smokers who smoked 1-19 mg Federal Trade Commission tar cigarettes, using their own brands ad libitum. Filters were analyzed to estimate the daily mouth exposure of nicotine. Twenty-four-hour urine samples were collected and analyzed for nicotine, cotinine, and 3'-hydroxycotinine plus their glucuronide conjugates. Saliva samples were collected daily for cotinine analysis.

RESULTS

Each method correlated significantly (p < 0.01) with the other two. The best correlation was between the mouth exposure of nicotine, as estimated by filter analysis, and urinary nicotine plus metabolites. Multiple regression analysis implies that saliva cotinine and urinary output are dependent on nicotine mouth exposure for multiple days. Creatinine normalization of the urinary metabolites degrades the correlation with mouth exposure.

CONCLUSIONS

The filter analysis method was shown to correlate with more traditional methods of estimating nicotine uptake. However, because filter analysis is less complicated and intrusive, subjects can collect samples easily and unsupervised. This should enable improvements in study compliance and future study designs.

Racial and ethnic differences in lung cancer incidence: how much is explained by differences in smoking patterns? (United States)

OBJECTIVES

Lung cancer rates vary considerably among U.S. racial/ethnic groups. We quantitatively analyzed the extent to which these differences can be attributed to differential patterns of smoking.

METHODS

We utilized survey data from the U.S. Census to estimate smoking patterns in the following racial/ethnic groups: non-Hispanic whites, non-Hispanic blacks, Hispanics, Asian/Pacific Islanders and American Indians. We used several dose-response models of smoking and lung cancer to predict relative lung cancer rates in these groups based on reported smoking patterns, specifically, on smoking status (current, former, never), cigarettes per day, age started, and age quit (for former smokers). Predicted rates were compared to observed population rates for these groups.

RESULTS

Black men had slightly lower predicted lung cancer rates than white men, but had 35-47% higher observed rates. Hispanic men had predicted rates about 25% lower than whites but observed rates 50% lower than whites; predicted rates for Hispanic women were 50% lower than whites compared to observed rates that were 60-70% lower. For Asian/Pacific Islanders, predicted and observed rates relative to whites were comparable. Predicted rates for American Indians were slightly higher than whites while observed rates were about 40% lower.

CONCLUSION

Differences in smoking largely explain lower lung cancer rates in Asian/Pacific Islanders relative to whites and partially explain lower rates in Hispanics compared to whites. Increased rates in black men and decreased rates in American Indians are not explained by differences in smoking.

Disparities in Lung Cancer: Focus on Asian Americans and Pacific Islanders, American Indians and Alaska Natives, and Hispanics and Latinos

Significant population changes in the United States are expected over the next few decades. The changing demographics inclusive of native and newly native individuals will significantly impact health care because racial and ethnic groups vary widely in their risks for disease and approach to medical care. For lung cancer specifically, racial and ethnic groups differ in smoking habits, metabolism of nicotine, presentation, stage at diagnosis, treatment received, and outcomes. This article summarizes current information on lung cancer for American and Pacific Islanders, American Indians and Alaska natives,and Hispanics and Latinos with an emphasis on tobacco use, epidemiologic issues sur-rounding acculturation and assimilation, genetic epidemiology, and disparities in treatment outcomes.

Smoking as a complex but critical covariate in neurobiological studies of posttraumatic stress disorders: a review

As smoking rates in the general population continue to fall in response to new information and changing social values, the continued high rate of smoking among persons with psychiatric disorders has caught the attention of society at many levels: public health officials, medical and mental health care providers, and concerned family members alike. As a consequence, research studies aimed at quantifying the problem and understanding its cause have increased dramatically over the past several years. The following review first examines epidemiological studies that have revealed a bidirectional causal relationship between tobacco dependence and posttraumatic stress disorder (PTSD), one of several mental health disorders in which tobacco dependence remains prevalent and resistant to intervention. Second, we use a translational neuroscience perspective to discuss possible neurobiological mediators of the relationship between PTSD and tobacco dependence, hoping to spur further human and animal research that will elucidate pathogenetic mechanisms involved and inspire novel treatment interventions. Finally, to enable more effective clinical research in this area, we provide an overview of effective scientific methods for assessing and managing 'smoking status' as an experimental variable in clinical research studies of PTSD as well as other mental health disorders.

Biological research on drug abuse and addiction in Hispanics: current status and future directions

Impressive progress has been made in the understanding of biological contributions to drug abuse and addiction. An area that has only recently begun to receive attention is potential ethnic and racial differences in biological systems that contribute to, or protect from, problem drug use. This article reviews recent research on drug abuse and addiction in Hispanics in which biological questions have been addressed, including work on genes, gene products (proteins), physiology and pharmacotherapy. Taken together, work to date suggests that there are both similarities and differences between Hispanics and other ethnic groups in biological factors related to drug abuse and addiction. Although the results are intriguing, relatively few studies have been done, and those that have been done have often been inconclusive due to low numbers of Hispanic subjects. Moreover, studies have often failed to recognize the complexity and heterogeneity of Hispanic populations in the United States and around the world. After reviewing the current status of the field, recommendations are given for future research in both humans and relevant animal models that will lead to a better understanding of drug abuse and addiction in Hispanics.

Tailoring nicotine replacement therapy: rationale and potential approaches

Nicotine replacement therapy (NRT) is an effective treatment for smoking cessation, but as with all such pharmacotherapies, the majority of smokers who use NRT products do not stop smoking or remain abstinent long term. Treatment outcome is affected by a range of individual-specific factors, as well as the pharmacokinetic profile of each NRT formulation. This has led to speculation that abstinence rates could be improved if NRT treatments were individually tailored to best match each individual's needs and preferences. There are also populations for whom special product and dosage considerations are warranted to maximise treatment safety.This paper reviews the rationale for NRT treatment, standard dose recommendations and recommendations for how to best match NRT treatment to the specific needs of individual smokers. We also review emerging evidence that genetic profiling may one day be a useful consideration for tailoring NRT treatment.

Effects of a nicotine conjugate vaccine on the acquisition and maintenance of nicotine self-administration in rats

RATIONALE

Immunization of rats against nicotine using a nicotine conjugate vaccine reduces the distribution of nicotine to brain in rats and attenuates some of nicotine's physiological and behavioral effects. It is not known whether such a vaccine can attenuate nicotine's reinforcing effects.

OBJECTIVE

The present experiment was conducted to determine whether a nicotine conjugate vaccine could interfere with the acquisition and maintenance of nicotine self-administration (NSA) in rats given 23 h day(-1) access to nicotine.

METHODS

To examine acquisition of NSA, rats were vaccinated with nicotine or control immunogen prior to being given access to a 0.01 mg kg(-1) infusion(-1) nicotine under a fixed-ratio(FR) 1 schedule for week 1, FR 2 for week 2, and FR 3 for week 3. Acquisition of cocaine self-administration (CSA) was similarly examined to determine the specificity of vaccination effects. To examine maintenance of NSA, rats were initially trained to self-administer nicotine under an FR 3 schedule, and then vaccinated with nicotine or control immunogen while NSA continued to be monitored.

RESULTS

NSA was significantly lower in vaccinated rats compared to controls during the acquisition protocol, with a 38% decrease in the number of infusions during the last week of training. The percentage of rats meeting acquisition criteria in the vaccinated group was lower (36%) than that in the control group (70%), but this difference was not statistically significant. Vaccination did not affect acquisition of CSA, demonstrating its specificity for nicotine. Maintenance of NSA was significantly reduced in vaccinated rats as compared to controls after the final vaccine injection, with a mean reduction of 57%. There was no evidence in either protocol that vaccinated rats attempted to compensate for altered nicotine distribution by increasing nicotine intake.

CONCLUSION

These data suggest that vaccination against nicotine can reduce the reinforcing effects of nicotine in rats and may have therapeutic potential for the treatment of tobacco dependence.

Current status of immunologic approaches to treating tobacco dependence: vaccines and nicotine-specific antibodies

In contrast to current pharmacotherapies, immunologic approaches to treating tobacco dependence target the drug itself rather than the brain. This approach involves the use of nicotine-specific antibodies that bind nicotine in serum, resulting in a decrease in nicotine distribution to the brain and an increase in nicotine's elimination half-life. This review summarizes the literature examining the effects of immunologic interventions on the pharmacokinetics and behavioral effects of nicotine in animal models, as well as recent phase I and II clinical trials in humans. Studies using various vaccines and nicotine-specific antibodies in rodents have shown that immunization can significantly reduce the behavioral effects of nicotine that are relevant to tobacco dependence (eg, nicotine self-administration). These findings provide proof of principle that immunologic interventions could have utility in the treatment of tobacco dependence. Thus far, phase I clinical trials of nicotine vaccines have not produced any serious adverse events in humans and have produced dose-dependent increases in serum antibody levels. Although preliminary data from these small trials suggest that vaccination can facilitate abstinence from tobacco use, more advance trials are needed. By acting outside the nervous system, immunologic approaches are less likely to produce the adverse side effects associated with current medications. In addition, the unique mechanism of action of immunotherapy makes it particularly suitable for combination with other pharmacological approaches. Taken together, the work completed to date provides substantial evidence that immunologic interventions could play an important role in future treatment strategies for tobacco dependence.

The influence of gender, race, and menthol content on tobacco exposure measures

Research has suggested that race, gender, and menthol cigarette use influence tobacco-smoke exposure measures and smoking-related disease risk. For example, a high proportion of Black smokers prefer menthol cigarettes and, despite smoking fewer cigarettes per day (CPD) than do Whites, tend to have higher cotinine levels. Additionally, Black males are more at risk for smoking-related lung cancer. High cotinine levels and smoking menthol cigarettes may lead to higher toxin intake, which contributes to increased disease risk. We explored the relationship between tobacco exposure variables (i.e., cotinine, CPD, carbon monoxide [CO], nicotine content, and nicotine dependence) with respect to race, gender, and menthol content in a sample of 307 smokers recruited from the greater Boston area to participate in a smoking cessation treatment trial. The pattern of correlations between tobacco exposure measures and cotinine showed a consistently positive correlation between cotinine and CO in all smokers and a correlation between cotinine and CPD in those who smoked nonmenthol cigarettes. Cotinine and CPD correlations varied by gender and race among menthol cigarette smokers. Consistently, we found a significant gender x race x menthol interaction on salivary cotinine level as well as cotinine/CPD ratio. These findings suggest that the relationship between number of cigarettes consumed and salivary cotinine is more complex than previously believed. It is not sufficient to look at race alone; researchers and clinicians need to look at race and gender concurrently, as well as type of cigarette consumed.

Nondaily smokers should be asked and advised to quit

BACKGROUND

Nondaily smokers are a growing subpopulation of smokers. Current cessation guidelines were developed for daily smokers, and how clinicians might help nondaily smokers is not clear.

METHODS

Analyzing the 2000 National Health Interview Survey in 2004, we compared characteristics of nondaily smokers with never smokers and daily smokers. We used multivariate logistic regression to compare predictors of wanting to quit in 6 months between nondaily and daily smokers.

RESULTS

About one in five current smokers was a nondaily smoker. Nondaily smokers reported better health than daily smokers, but had some health status indicators suggesting worse health than never smokers. Nondaily smokers were more likely to want to quit (odds ratio [OR]=1.31, 95% confidence interval [CI]=1.10-1.56) than daily smokers, but were less likely to report a physician having asked about tobacco use (41% vs 50%, p<0.0001) or advised quitting (31% vs 41%, p<0.0001). In both nondaily and daily smokers, physician advice (nondaily OR=1.50, 95% CI=1.03-2.2; daily OR=1.58, 95% CI=1.32-1.89), and the belief that secondhand smoke harms others (nondaily OR=1.48, 95% CI=1.04-2.1; daily OR=1.80, 95% CI=1.56-2.1), predicted wanting to quit. Higher-educated nondaily smokers were less likely to want to quit (OR=0.54, 95% CI=0.32-0.91), unlike in daily smokers (OR=1.48, 95% CI=1.15-1.89). Latino nondaily smokers were less likely (OR=0.43, 95% CI=0.30-0.64) than whites, and African-American daily smokers were more likely (OR=1.27, 95% CI=1.04-1.55) than whites, to want to quit.

CONCLUSIONS

While daily smokers may seem a higher cessation priority, nondaily smokers may be more likely to quit with brief interventions. Cessation messages should address health risks of any smoking, ethnic differences, smoke-free messages, and situational triggers.

Phase I pharmacokinetic study of S-1 plus cisplatin in patients with advanced gastric carcinoma

PURPOSE

The conversion rate of tegafur (a component of S-1) to fluorouracil (FU) differs in Asians and whites because of polymorphic differences in the CYP2A6 gene. S-1 with cisplatin is considered highly active in Japanese gastric cancer patients. Therefore, we initiated a phase I pharmacokinetic study of this combination in our gastric cancer patients.

PATIENTS AND METHODS

Patients received cisplatin intravenously on day 1 and S-1 orally, twice daily, on days 1 to 21 every 28 days. At level 1, the S-1 dose was 25 mg/m2/dose (50 mg/m2/d), but it was increased by 5 mg/m2/dose for the next level. Cisplatin was administered at 75 mg/m2 (for levels 1 and 2) but was then reduced to 60 mg/m2 (level 1A). At every level, a cohort of three patients, which could be expanded to six patients, was studied. Maximum-tolerated dose (MTD) was determined based on the dose-limiting toxicity (DLT) in the first cycle. Patients with histologic proof of gastric adenocarcinoma and near-normal organ function were studied.

RESULTS

Sixteen patients were enrolled. No DLTs occurred at level 1. However, DLTs occurred at levels 2 and 1A. The area under the curve for FU correlated significantly with DLT (P = .006) and grade 3 to 4 diarrhea (P = .004). Six partial responses were confirmed, including three at the MTD.

CONCLUSION

At the established MTD of S-1 plus cisplatin, the S-1 dose (50 mg/m2/d for 21 days) is lower in our study than in the Japanese study (80 mg/m2/d for 21 days). A multi-institutional phase II study of this active combination is currently accruing patients.

Validation and application of a method for the determination of nicotine and five major metabolites in smokers' urine by solid-phase extraction and liquid chromatography-tandem mass spectrometry

An SPE-LC-MS/MS method was developed, validated and applied to the determination of nicotine and five major metabolites in human urine: cotinine, trans-3'-hydroxycotinine, nicotine-N-glucuronide, cotinine-N-glucuronide and trans-3'-hydroxycotinine-O-glucuronide. A 500 microL urine sample was pH-adjusted with phosphate buffer (1.5 mL) containing nicotine-methyl-d3, cotinine-methyl-d3 and trans-3'-hydroxycotinine-methyl-d3 internal standards. For the unconjugated metabolites, an aliquot (800 microL) of the buffered solution was applied to a 30 mg Oasis HLB-SPE column, rinsed with 2% NH4OH/H2O (3.0 mL) and H2O (3.0 mL) and eluted with methanol (500 microL). The eluate was analyzed isocratically (100% methanol) by LC-MS/MS on a diol column (50 x 2.1 mm). For the total metabolites, a beta-glucuronidase/buffer preparation (100 microL) was added to the remaining buffered solution and incubated at 37 degrees C (20 h). An aliquot (800 microL) of the enzymatically treated buffered solution was extracted and analyzed in the same manner. The conjugated metabolites were determined indirectly by subtraction. The quantitation range of the method (ng/mL) was 14-10,320 for nicotine, 15-9800 for cotinine and 32-19,220 for trans-3'-hydroxycotinine. The validated method was used to observe diurnal variations from a smoker's spot urine samples, elimination half-lives from a smoker's 24 h urine samples and metabolite distribution profiles in the spot and 24 h urine samples.

Nicotine metabolism: the impact of CYP2A6 on estimates of additive genetic influence

To conduct a pharmacogenetic investigation of nicotine metabolism in twins. One hundred and thirty nine twin pairs [110 monozygotic (MZ) and 29 dizygotic (DZ)] underwent a 30-min infusion of stable isotope-labelled nicotine and its major metabolite, cotinine, followed by an 8-h in-hospital stay. Blood and urine samples were taken at regular intervals for analysis of nicotine, cotinine and metabolites by gas chromatography-mass spectrometry or liquid chromatography-mass spectrometry and subsequent characterization of pharmacokinetic and metabolism phenotypes. DNA was genotyped to confirm zygosity and for variation in the gene for the primary enzyme involved in nicotine metabolism, CYP2A6 (alleles tested: *1, *1x2, *2, *4, *7, *9 and *12). Univariate biometric analyses quantified genetic and environmental influences on each pharmacokinetic measure in the presence and absence of covariates, including measured CYP2A6 genotype. The best-fitting model identified a substantial amount of variation in the weight-adjusted rate of total clearance of nicotine attributable to additive genetic influences [59.4%, 95% confidence interval (CI)=44.7-70.7]. The majority of variation in the clearance of nicotine via the cotinine pathway was similarly genetically influenced (60.8%, 95% CI=46.9-71.5). Heritability estimates were reduced to 54.2% and 51.8%, respectively, but remained substantial after taking into account the effect of variation in CYP2A6 genotype. These results suggest the involvement of additional genetic factors (e.g. uncharacterized or novel CYP2A6 alleles as well as other genes in the metabolic pathway) that remain to be identified.

Effect of cigarette smoking on gastric emptying of solids in Japanese smokers: a crossover study using the 13C-octanoic acid breath test

BACKGROUND

Cigarette smoking is associated with an increased risk of peptic ulcer and gastroesophageal reflux disease. Gastric emptying disorders may play a role in the development of these upper gastrointestinal diseases. Thus, studies examining a link between smoking and gastric emptying disorders have clinical relevance. This study was conducted to investigate the effect of smoking on gastric emptying of solids in Japanese smokers.

METHODS

The (13)C-octanoic acid breath test was performed in eight male habitual smokers on two randomized occasions (either sham smoking or actively smoking). The time vs (13)CO(2) excretion rate curve was mathematically fitted to a conventional formula of y (t) = m*k*beta*e(-k*t)*(1 - e(-k*t))(beta-1), and the parameters of k and beta were determined: under the crossover protocol, a larger (smaller) beta indicates slower (faster) emptying in the early phase, and a larger (smaller) k indicates faster (slower) emptying in the later phase. The half (13)CO(2) excretion time (t(1/2b) = -[ln(1 - 2(-1/beta))]/k) and the time of maximal (13)CO(2) excretion rate (t(max) = [lnbeta]/k) were also calculated. Between the two occasions, k, beta, t(1/2b), and t(max) were compared by the Wilcoxon signed-rank test.

RESULTS

After smoking, k was significantly increased. No significant differences were found in beta, t(1/2), and t(max) between the two occasions.

CONCLUSIONS

The increase in k suggests the acceleration of gastric emptying in the later phase. For the first time, this study has revealed that acute smoking speeds the gastric emptying of solids in Japanese habitual smokers.

Monoclonal nicotine-specific antibodies reduce nicotine distribution to brain in rats: dose- and affinity-response relationships

Vaccination against nicotine is being studied as a potential treatment for nicotine dependence. Some of the limitations of vaccination, such as variability in antibody titer and affinity, might be overcome by instead using passive immunization with nicotine-specific monoclonal antibodies. The effects of antibodies on nicotine distribution to brain were studied using nicotine-specific monoclonal antibodies (NICmAbs) with K(d) values ranging from 60 to 250 nM and a high-affinity polyclonal rabbit antiserum (K(d) = 1.6 nM). Pretreatment with NICmAbs substantially increased the binding of nicotine in serum after a single nicotine dose, reduced the unbound nicotine concentration in serum, and reduced the distribution of nicotine to brain. Efficacy was directly related to antibody affinity for nicotine. Efficacy of the highest affinity NICmAb, NICmAb311, was dose-related, with the highest dose reducing nicotine distribution to brain by 78%. NICmAb311 decreased nicotine clearance by 90% and prolonged the terminal half-life of nicotine by 120%. At equivalent doses, NICmAb311 was less effective than the higher affinity rabbit antiserum but comparable efficacy could be achieved by increasing the NICmAb311 dose. These data suggest that passive immunization with nicotine-specific monoclonal antibodies substantially alters nicotine pharmacokinetics in a manner similar to that previously reported for vaccination against nicotine. Antibody efficacy is a function of both dose and affinity for nicotine.

Racial differences in exposure to environmental tobacco smoke among children

Exposure to environmental tobacco smoke (ETS) is a major cause of morbidity and mortality among U.S. children. Despite African-American children's having a lower reported exposure to tobacco compared to whites, they suffer disproportionately from tobacco-related illnesses and have higher levels of serum cotinine than white children. The goal of this study was to test whether African-American children have higher levels of serum and hair cotinine, after accounting for ETS exposure and various housing characteristics. We investigated the level of cotinine in both hair and serum in a sample of 222 children with asthma. Using a previously validated survey for adult smokers, we assessed each child's exposure to ETS. We collected detailed information on the primary residence, including home volume, ventilation, and overall home configuration. Despite a lower reported ETS exposure, African-American children had higher mean levels of serum cotinine (1.41 ng/mL vs. 0.97 ng/mL; p = 0.03) and hair cotinine (0.25 ng/mg vs. 0.07 ng/mg; p < 0.001) compared with white children. After adjusting for ETS exposure, housing size, and other demographic characteristics, serum and hair cotinine levels remained significantly higher in African-American children (ss = 0.34, p = 0.03) than in white children (ss = 1.06, p < 0.001). Housing volume was significantly associated with both serum and hair cotinine but did not fully explain the race difference. Our results demonstrate that, despite a lower reported exposure to ETS, African-American children with asthma had significantly higher levels of both serum and hair cotinine than did white children. Identifying causes and consequences of increased cotinine may help explain the striking differences in tobacco-related illnesses.

Nicotine delivery capabilities of smokeless tobacco products and implications for control of tobacco dependence in South Africa

OBJECTIVES

Smokeless tobacco (SLT) use is popular among black South African women and children. The study sought to determine the nicotine delivery capability of popular industrialised and traditional SLT brands in South Africa, and to provide information for policy action by regulatory authorities.

DESIGN

Laboratory chemical analysis of four industrialised and one traditional SLT products commercially available, using previously published analytical methods. Potential for dependence was inferred from nicotine delivery capabilities determined by the percentage free base nicotine.

MEASUREMENTS

Moisture, pH, total nicotine, and percentage free base nicotine.

RESULTS

Total nicotine content was between 6-16 mg/g. The pH varied between 7-10 and this correlated with percentage free base nicotine, which ranged between 10-99%. The nicotine delivery capability of the traditional product was lower than that of the industrialised products except for the recently introduced portion bag snus, which had comparable total nicotine but the lowest pH and percentage free base nicotine. The most popular SLT brands showed the highest percentage free base nicotine ever reported for any industrialised SLT or cigarette brands. Small cans contained higher nicotine than the large cans of the same brand tested. Findings from the study support a potential for limited "product graduation" by users.

CONCLUSIONS

South African SLT users are mostly exposed to potentially very highly addictive levels of nicotine that may favour tobacco dependence and its consequent health risks. The increasing use of SLT by women of childbearing age support the need for intensified policy action to control its use.

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.

Differences in drug pharmacokinetics between East Asians and Caucasians and the role of genetic polymorphisms

Interethnic variability in pharmacokinetics can cause unexpected outcomes such as therapeutic failure, adverse effects, and toxicity in subjects of different ethnic origin undergoing medical treatment. It is important to realize that both genetic and environmental factors can lead to these differences among ethnic groups. The International Conference on Harmonization (ICH) published a guidance to facilitate the registration of drugs among ICH regions (European Union, Japan, the United States) by recommending a framework for evaluating the impact of ethnic factors on a drug's effect, as well as its efficacy and safety at a particular dosage and dosage regimen. This review focuses on the pharmacokinetic differences between East Asians and Caucasians. Differences in metabolism between East Asians and Caucasians are common, especially in the activity of several phase I enzymes such as CYP2D6 and the CYP2C subfamily. Before drug therapy, identification of either the genotype and/or the phenotype for these enzymes may be of therapeutic value, particularly for drugs with a narrow therapeutic index. Furthermore, these differences are relevant for international drug approval when regulatory agencies must decide if they accept results from clinical trials performed in other parts of the world.

N-glucuronidation of nicotine and cotinine by human liver microsomes and heterologously expressed UDP-glucuronosyltransferases

Nicotine is considered the major addictive agent in tobacco. Tobacco users extensively metabolize nicotine to cotinine. Both nicotine and cotinine undergo N-glucuronidation. Human liver microsomes have been shown to catalyze the formation of these N-glucuronides. However, which UDP-glucuronosyltransferases contribute to this catalysis has not been identified. To identify these enzymes, we initially measured the rates of glucuronidation by 15 human liver microsome samples. Fourteen of the samples glucuronidated both nicotine and cotinine at rates ranging from 146 to 673 pmol/min/mg protein and 140 to 908 pmol/min/mg protein, respectively. The rates of nicotine glucuronidation and cotinine glucuronidation by these 14 samples were correlated, r = 0.97 (p < 0.0001). The glucuronidation of nicotine and cotinine by heterologously expressed UGT1A3, UGT1A4, and UGT1A9 was also determined. All three enzymes catalyzed the glucuronidation of nicotine. However, the rate of catalysis by UGT1A4 Supersomes was more than 30-fold greater than that by either UGT1A3 Supersomes or UGT1A9 Supersomes. Interestingly, when expressed per UGT1A protein, measured by a UGT1A specific antibody, cell lysate from V79-expressed UGT1A9 catalyzed nicotine glucuronidation at a rate 17-fold greater than did UGT1A9 Supersomes. UGT1A4 Supersomes also catalyzed cotinine N-glucuronidation, but at one-tenth the rate of nicotine glucuronidation. Cotinine glucuronidation by either UGT1A3 or UGT1A9 was not detected. Both propofol, a UGT1A9 substrate, and imipramine, a UGT1A4 substrate, inhibited the glucuronidation of nicotine and cotinine by human liver microsomes. Taken together, these data support a role for both UGT1A9 and UGT1A4 in the catalysis of nicotine and cotinine N-glucuronidation.

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.

Watson and Crick 50 years on. From double helix to pharmacogenomics

The second half of the 20th century has seen quantum leaps in our understanding of molecular biology. The technological advances, which facilitated the recent successful completion of the Human Genome Project, have provided the tools for deciphering the complexity of the human condition. At present, the function of only 50% of genes is known. However, as understanding of the human genome improves, a plethora of gene targets for treating disease will be uncovered - leading to therapies which will be considered revolutionary. Genome related science has begun to impact almost every facet of medicine including anaesthesia and intensive care. Better understanding of interindividual differences will enable better prediction of illness susceptibility as well as response to treatment. These insights will permit therapies to be tailored to individuals or racial groups. At present, there is only rudimentary knowledge of factors controlling gene regulation, but in the future, better understanding of gene-environment interactions and gene expression will enable pharmaceutical companies to develop new therapies and permit clinicians to optimise their effects, without recourse to current laborious testing regimens. As genomic science progresses, new ethical, legal, social and philosophical dilemmas will also continue to emerge.

Pulmonary function as a predictor of lung cancer mortality in continuing cigarette smokers and in quitters

BACKGROUND

Forced expiratory volume in 1 second (FEV(1)) may be useful for identifying smokers at higher risk of lung cancer. We examined the association of FEV(1) with lung cancer mortality (LCM) among cigarette smokers in the Multiple Risk Factor Intervention Trial (MRFIT).

METHODS

In all, 6613 MRFIT baseline smokers alive at trial end in 1982 had acceptable FEV(1) measures and complete smoking history; men were classified as during-trial long-term quitters (N = 1292), intermittent quitters (1961), and never quitters (3360). Proportional hazards models for LCM were fit with quintiles of average FEV(1), adjusted for age, height, race, smoking history, and other risk factors.

RESULTS

For long-term, intermittent, and never quitters respectively, mean baseline cigarettes/ day was 28, 32, and 35; trial-averaged FEV(1) was 3201, 3146, and 3082 ml; and average decline in FEV(1) was -46.0, -54.6, and -62.5 ml/year. With median post-trial mortality follow-up of 18 years, there were 363 lung cancer deaths. Age-adjusted LCM rates varied across FEV(1) quintiles from 50 (lowest quintile) to 11 (highest quintile), 58 to 11, and 76 to 20, per 10 000 person-years, for long-term quitters, intermittent quitters, and never quitters, respectively. Multivariate adjusted hazard ratios for 100 ml higher FEV(1) were 0.92 [P = 0.004], 0.95 [P = 0.003], and 0.95 [P < 0.0001] respectively.

CONCLUSIONS

These results demonstrate the strong predictive value of FEV(1) for lung cancer among cigarette smokers independent of smoking history; results did not differ by during-trial quit status. FEV(1) may be a biological marker for smoking dose or it may be that genetic susceptibilities to both decreased FEV(1) and lung cancer are associated.

Tobacco cessation in primary care: maximizing intervention strategies

The most effective preventive intervention that a clinician can provide for tobacco-using patients against heart disease, cancer, cerebrovascular disease and chronic obstructive pulmonary disease is an empathic, personalized smoking cessation intervention program with extended assistance and follow-up. The goal of the intervention must be complete smoking cessation. Reduction provides no direct health benefits to the individual smoker. Interventions are readily available, but underutilized, in part due to lack of clinician training and organizational support. The present article summarizes the current guidelines for smoking cessation interventions as a framework from which to start. The guidelines incorporate the Transtheoretical Model of patient behavioral change and the "Five A's": Ask, Advise, Assess, Assist and Arrange. Pharmacotherapeutic tools, including nicotine replacement therapies (nicotine gums, patches, nasal sprays, inhalers and new therapies) and non-nicotine therapies (bupropion, clonidine, nortriptyline and other antidepressants and anxiolytics) are considered. Adherence validation methods, new approaches to tobacco and addiction treatment that appear in the recent research literature are reviewed. Beyond this framework, specific categories of tobacco users (including smokeless tobacco users), cultural and ethnic minorities, adolescents using snuff and bidis, women, Medicaid recipients, and users of multiple forms of tobacco require special consideration. With this framework and the modifications that may be required for specific categories of patients, practicing clinicians can incorporate into daily practice a successful tobacco cessation intervention program with quit rates approaching 20%.

Cognitive effects of nicotine in humans: an fMRI study

To elucidate the neural correlates of cognitive effects of nicotine, we examined behavioral performance and blood oxygenation level-dependent regional brain activity, using functional magnetic resonance imaging, during a parametric "n-back" task in healthy nonsmoking males after the administration of nicotine (12 microg/kg body weight) or saline. Nicotine, compared to placebo, improved accuracy (P = 0.008) in all active conditions (2%-11%), and had a load-specific effect on latency (P = 0.004; 43.78% decrease at the highest memory load). Within a network of parietal and frontal areas activated by the task (P < 0.05, corrected at the voxel level), nicotine produced an increased response (P < 0.05; uncorrected within the regions of interest) in the anterior cingulate, superior frontal cortex, and superior parietal cortex. It also produced an increased response in the midbrain tectum in all active conditions and in the parahippocampal gyrus, cerebellum, and medial occipital lobe during rest (P = 0.05; uncorrected). The present observations point to altered neuronal activity in a distributed neural network associated with on-line task monitoring and attention and arousal systems as underlying nicotine-related enhancement of attention and working memory in human subjects.

Nicotine metabolism, human drug metabolism polymorphisms, and smoking behaviour

Large interindividual differences occur in human nicotine disposition, and it has been proposed that genetic polymorphisms in nicotine metabolism may be a major determinant of an individual's smoking behaviour. Hepatic cytochrome P4502A6 (CYP2A6) catalyses the major route of nicotine metabolism: C-oxidation to cotinine, followed by hydroxylation to trans-3'-hydroxycotinine. Nicotine and cotinine both undergo N-oxidation and pyridine N-glucuronidation. Nicotine N-1-oxide formation is catalysed by hepatic flavin-containing monooxygenase form 3 (FMO3), but the enzyme(s) required for cotinine N-1'-oxide formation has not been identified. trans-3'-Hydroxycotinine is conjugated by O-glucuronidation. The uridine diphosphate-glucuronosyltransferase (UGT) enzyme(s) required for N- and O-glucuronidation have not been identified. CYP2A6 is highly polymorphic resulting in functional differences in nicotine C-oxidation both in vitro and in vivo; however, population studies fail to consistently and conclusively demonstrate any associations between variant CYP2A6 alleles encoding for either reduced or enhanced enzyme activity with self-reported smoking behaviour. The functional consequences of FMO3 and UGT polymorphisms on nicotine disposition have not been investigated, but are unlikely to significantly affect smoking behaviour. Therefore, current evidence does not support the hypothesis that genetic polymorphisms associated with nicotine metabolism are a major determinant of an individual's smoking behaviour and exposure to tobacco smoke.