Showing papers by "Neal L. Benowitz published in 2007"

Guidelines on nicotine dose selection for in vivo research

Abstract: 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.

The pharmacogenetics research network: from SNP discovery to clinical drug response.

Abstract: The NIH Pharmacogenetics Research Network (PGRN) is a collaborative group of investigators with a wide range of research interests, but all attempting to correlate drug response with genetic variation. Several research groups concentrate on drugs used to treat specific medical disorders (asthma, depression, cardiovascular disease, addiction of nicotine, and cancer), whereas others are focused on specific groups of proteins that interact with drugs (membrane transporters and phase II drug-metabolizing enzymes). The diverse scientific information is stored and annotated in a publicly accessible knowledge base, the Pharmacogenetics and Pharmacogenomics Knowledge base (PharmGKB). This report highlights selected achievements and scientific approaches as well as hypotheses about future directions of each of the groups within the PGRN. Seven major topics are included: informatics (PharmGKB), cardiovascular, pulmonary, addiction, cancer, transport, and metabolism.

Vaporization as a smokeless cannabis delivery system: a pilot study.

Abstract: Although cannabis may have potential therapeutic value, inhalation of a combustion product is an undesirable delivery system. The aim of the study was to investigate vaporization using the Volcano® device as an alternative means of delivery of inhaled Cannabis sativa. Eighteen healthy inpatient subjects enrolled to compare the delivery of cannabinoids by vaporization to marijuana smoked in a standard cigarette. One strength (1.7, 3.4, or 6.8% tetrahydrocannabinol (THC)) and delivery system was randomly assigned for each of the 6 study days. Plasma concentrations of Δ-9-THC, expired carbon monoxide (CO), physiologic and neuropsychologic effects were the main outcome measures. Peak plasma concentrations and 6-h area under the plasma concentration–time curve of THC were similar. CO levels were reduced with vaporization. No adverse events occurred. Vaporization of cannabis is a safe and effective mode of delivery of THC. Further trials of clinical effectiveness of cannabis could utilize vaporization as a smokeless delivery system. Clinical Pharmacology & Therapeutics (2007) 82, 572–578; doi:10.1038/sj.clpt.6100200; published online 11 April 2007

Translational research in medication development for nicotine dependence

Abstract: In their Review, the authors describe animal and human laboratory paradigms used to investigate the pathophysiology of nicotine dependence, and propose how their predictive clinical validity might be improved, thereby enhancing the development of new medications for smoking cessation. A major obstacle to the development of medications for nicotine dependence is the lack of animal and human laboratory models with sufficient predictive clinical validity to support the translation of knowledge from laboratory studies to clinical research. This Review describes the animal and human laboratory paradigms commonly used to investigate the pathophysiology of nicotine dependence, and proposes how their predictive validity might be determined and improved, thereby enhancing the development of new medications.

Nicotine and Carcinogen Exposure with Smoking of Progressively Reduced Nicotine Content Cigarette

Abstract: Background: Reducing the nicotine content of cigarettes to make them non-addictive has been widely discussed as a potential strategy for tobacco regulation. A major concern with nicotine reduction is that smokers will compensate for reduced nicotine by smoking more cigarettes and/or smoking more intensively, thereby increasing their exposure to tobacco smoke toxins. This study examined whether gradual reduction in nicotine exposure increases exposure to tobacco smoke toxins. Methods: This 10-week longitudinal study of 20 healthy smokers involved smoking their usual brand followed by different types of research cigarettes with progressively lower nicotine content, each smoked for 1 week. Subjects were followed for 4 weeks after returning to smoking their usual brand (or quitting). Smoking behaviors, chemical biomarkers of tobacco smoke exposure, and cardiovascular effect biomarkers were measured. Findings: Intake of nicotine declined progressively as the nicotine content of cigarettes was reduced, with little evidence of compensation. Cigarette consumption and markers of exposure to carbon monoxide and polycyclic aromatic hydrocarbons, as well as cardiovascular biomarkers remained stable, whereas urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol excretion decreased. Twenty-five percent of participants had spontaneously quit smoking 4 weeks after completing the research cigarette taper. Implications: Our findings with reduced nicotine content cigarettes differ from those of commercial low yields for which compensatory smoking for lower nicotine delivery is substantial. Our data suggest that the degree of nicotine dependence of smokers can be lowered without increasing their exposure to tobacco smoke toxins. Gradual reduction of nicotine content of cigarettes seems to be feasible and should be further evaluated as a national tobacco regulatory strategy. (Cancer Epidemiol Biomarkers Prev 2007;16(11):2479–85)

CHRNA4 and Tobacco Dependence From Gene Regulation to Treatment Outcome

Abstract: Context Given the probable importance of the α4 subunit of the neuronal nicotinic acetylcholine receptor, the gene that codes for this subunit ( CHRNA4 ) represents an excellent starting point for a genetic investigation of smoking behavior. Objective To achieve a better understanding of the role of this gene in the cause and treatment of tobacco dependence, we adopted a transdisciplinary pharmacogenetic approach. Design Study at the behavioral and clinical levels of analysis. Setting Academic research. Participants Smokers (n = 316) between the ages of 18 and 50 years were recruited from the Denver, Colorado, metropolitan area. Main Outcome Measures Bioinformatics analyses, cell culture experiments, and analyses of CHRNA4 expression and nicotine binding in postmortem human brain tissue advanced 2 single-nucleotide polymorphisms ( rs6122429 and rs2236196 ). Results Both single-nucleotide polymorphisms were associated with subjective responses to smoking in the laboratory among 316 smokers. Likewise, among 353 participants in a clinical trial, rs2236196 was associated with smoking cessation outcomes. Conclusions Results of analyses ranging from basic biological approaches to clinical outcome data provide consistent evidence that 2 single-nucleotide polymorphisms in CHRNA4 are functional at a biological level and are associated with nicotine dependence phenotypes. This interdisciplinary approach to the genetics of nicotine dependence provides a model for testing how functional genetic variation is translated from changes in messenger RNA and protein to individual differences in behavior and treatment outcome.

Determination of phenolic metabolites of polycyclic aromatic hydrocarbons in human urine as their pentafluorobenzyl ether derivatives using liquid chromatography-tandem mass spectrometry.

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental contaminants, and a number of them are carcinogenic. One approach for measuring exposure to them is to determine the concentrations of metabolites in urine. The pyrene metabolite 1-hydroxypyrene has been used as a biomarker for exposure in numerous studies. However, determination of exposure to several PAHs may be advantageous, since the relative amounts may vary depending upon the exposure source. We developed a liquid chromatography−tandem mass spectrometry method for the determination of phenolic metabolites of naphthalene, fluorene, phenanthrene, and pyrene in human urine. Following enzymatic cleavage of the glucuronide and sulfate conjugates, the phenolic metabolites are extracted from urine and converted to pentafluorobenzyl ethers. These derivatives greatly enhance the sensitivity of detection by atmospheric pressure chemical ionization in the negative ion mode. Lower limits of quantitation range from 0.01 to 0.5 ng/mL. Stable iso...

Urine Nicotine Metabolites and Smoking Behavior in a Multiracial/Multiethnic National Sample of Young Adults

Abstract: Nicotine metabolism has been hypothesized to affect patterns of smoking. The recent development of a noninvasive measure of nicotine metabolism, the nicotine metabolite ratio (trans-3'-hydroxycotinine/cotinine), makes it possible to examine the association between rate of nicotine metabolism and smoking behavior in the general population. This US study examined group differences in the ratio measured in urine and the association between the ratio and multiple measures of smoking behavior and nicotine dependence in a large, national representative sample of young adults. The sample included 900 daily smokers aged 18-26 years from wave III (2001-2002) of the National Longitudinal Survey of Adolescent Health. Nicotine dependence was measured by using the Fagerstrom Test for Nicotine Dependence. Females had higher nicotine metabolite ratios than males; Whites and Hispanics had higher nicotine metabolite ratios than African Americans or Asians. This finding is consistent with those from laboratory studies of older smokers based on intravenous infusion of nicotine. No significant association was found between the nicotine metabolite ratio and number of cigarettes smoked per day or nicotine dependence. The availability of a noninvasive measure makes possible systematic testing of causal hypotheses generated by laboratory studies in the general population.

Higher Nicotine and Carbon Monoxide Levels in Menthol Cigarette Smokers With and Without Schizophrenia

Abstract: This study examined whether smoking menthol cigarettes was associated with increased biochemical measures of smoke intake. Expired carbon monoxide (CO) and serum nicotine and cotinine were measured in 89 smokers with schizophrenia and 53 control smokers immediately after smoking an afternoon cigarette. Serum nicotine levels (27 vs. 22 ng/ml, p = .010), serum cotinine levels (294 vs. 240 ng/ml, p = .041), and expired CO (25 vs. 21 ppm, p = .029) were higher in smokers of menthol compared with nonmenthol cigarettes, with no differences in 3-hydroxycotinine/cotinine ratios between groups when controlling for race. Backward stepwise linear regression models showed that, in addition to having a diagnosis of schizophrenia, smoking menthol cigarettes was a significant predictor of nicotine and cotinine levels. Individuals with schizophrenia or schizoaffective disorder smoked more generic or discount value brands (Basic, Doral, Monarch, USA, Wave, others) compared with control smokers (28% vs. 6%, p = .002) but did not smoke more brands with high nicotine delivery as estimated by the U.S. Federal Trade Commission method. Although rates of mentholated cigarette smoking were not higher in smokers with schizophrenia overall, they were significantly higher in non-Hispanic White people with schizophrenia compared with controls of the same ethnic/racial subgroup (51% vs. 28%, p<.0001). The higher exhaled CO in menthol smokers suggests that the higher nicotine levels are at least partly related to increased intake of smoke from menthol cigarettes, although menthol-mediated inhibition of nicotine metabolism also may be a factor. Menthol is an important cigarette additive that may help explain why some groups have lower quit rates and more smoking-caused disease.

CYP2B6 genotype does not alter nicotine metabolism, plasma levels, or abstinence with nicotine replacement therapy.

Abstract: CYP2A6 metabolically inactivates nicotine to cotinine and further metabolizes cotinine to 3-hydroxycotinine ([1][1], [2][2]). Genetically slow CYP2A6 activity reduces the rate of nicotine metabolism ([3][3]), reduces the 3′- trans -hydroxycotinine/cotinine (3HCOT/COT) ratio (a phenotypic measure

Mutagen Sensitivity and Genetic Variants in Nucleotide Excision Repair Pathway: Genotype-Phenotype Correlation

Abstract: The rationale behind gene-disease association studies is that genetic variants (polymorphisms) result in alterations in intermediate phenotypes. However, genotype-phenotype correlations have not been established for most polymorphisms. In this study, we correlated genotype data of genes involved in the nucleotide excision repair pathway with mutagen sensitivity phenotype, quantified by benzo(a)pyrene diol epoxide (BPDE)-induced chromatid breaks in peripheral blood lymphocytes in 422 healthy subjects recruited into a twin study that included 138 pairs of monozygotic twins, 51 pairs of dizygotic twins, and 44 siblings. Among a panel of single nucleotide polymorphisms examined, we found that BPDE sensitivity was modified by individual polymorphisms in XPC, RAD23B, and XPA genes. Specific haplotypes and diplotypes of XPC also modified BPDE sensitivity profiles. In addition, a more consistent and stronger correlation was observed between mutagen sensitivity phenotype and the combination of multiple polymorphisms in the nucleotide excision repair pathway. Specifically, when XPC-PAT, XPC Lys939Gln, XPA A23G, and RAD23B Val249Ala were analyzed together, we observed a significant dose-response relationship between increasing mutagen sensitivity with increasing number of adverse alleles: mutagen sensitivity for those carrying zero to two, three to five, and six or more adverse alleles were 0.64, 0.68, and 1.06, respectively (P for trend = 0.008), and the results remained significant after adjusting for multiple comparisons. Using individuals carrying zero to two adverse alleles as the reference group, the risks of being mutagen sensitive (mutagen sensitivity values greater than the median) were 1.05 (95% confidence interval, 0.68-1.64) and 4.48 (95% confidence interval, 1.21-16.61) for those carrying three to five and six or more adverse alleles, respectively. Analyses of the effects of genotype combinations yielded similar results. These findings underscore the importance of assessing the collective effects of a panel of polymorphisms in the same pathway in modulating mutagen sensitivity. As risk assessment for cancer risk is moving toward a multigenic pathway-based approach, future genotype-phenotype correlation studies should also investigate the combined effects of multiple genetic variants.

Cotinine levels in relation to smoking behavior and addiction in young adolescent smokers.

Abstract: The goal of this study was to identify associations among self-reported nicotine exposure, nicotine addiction, and actual nicotine intake as measured by salivary cotinine levels in adolescent smokers. A total of 170 adolescent smokers with a mean age of 15 years were recruited from seven northern Californian public high schools. Data were collected on smoking behaviors, addiction, craving, and withdrawal. Nicotine dependence was assessed using a modified teen Fagerstrom Tolerance Questionnaire (mtFTQ), a modified Nicotine Dependence Syndrome Scale (mNDSS), and a simple self-rating. Withdrawal was assessed using the Minnesota Withdrawal Questionnaire, and craving was assessed using a survey created by the authors. Salivary cotinine levels were collected from and analysed in participants who self-identified as smokers; data from the 54 participants who smoked in the past 4 days and whose salivary cotinine levels were greater than 0.1 ng/ml were used in the analysis. Among this group of adolescent smokers, the mean number of cigarettes smoked per day was 3.51 (SD = 3.44) and the mean level of salivary cotinine was 44.1 ng/ml (Mdn = 24.2). Even at this low level of nicotine exposure, cotinine was highly correlated with measures of nicotine dependence such as the mtFTQ (r = 0.497, p = .001), NDSS (r = 0.439, p = .002), timing of craving in the morning (r = -0.601, p = .000), and self-rated addiction (r = 0.562, p = .000). Most interesting, cotinine levels reached a plateau at around 4-5 cigarettes/day.

Prediction methods for nicotine clearance using cotinine and 3-hydroxy-cotinine spot saliva samples II. Model application.

Abstract: To develop and compare methods that predict individual nicotine (NIC) clearance, which reflects CYP2A6 activity, using random saliva cotinine (COT) and trans 3′-hydroxycotinine (3HC) measurements. COT and 3HC saliva concentrations in smokers were simulated utilizing a mechanistic population pharmacokinetic model of NIC metabolism that was adapted from the one described in a companion paper. Four methods to predict NIC clearance using the metabolites concentrations were compared. The precision bias, and the fraction of predictions that are made with an absolute error below 25% were the performance measures evaluated. Four prediction methods were compared: (M1) reference method, an intercept slope model of the metabolite concentration ratios ([3HC]/[COT]) (M2) an intercept slope model of the natural logarithm of the metabolite ratios (M3) a spline of the logarithm of the metabolite ratios (M4) Maximal Posteriori Bayesian estimate of NIC clearance conditioned on the model, COT and 3HC concentrations. In addition, the effect of smoking patterns on the concentrations of COT and 3HC was evaluated. The precision, accuracy, and the fraction of predictions with an absolute error below 25%, were higher for methods M2–M4 compared to method M1. However, the differences between M2 and M4 were small. Additionally, smoking pattern did not affect the metabolite concentration profiles. Predicting NIC clearance using an intercept slope model of the natural logarithm of the ratio of 3HC to COT appears to be a relatively simple method that is better than using the metabolite ratio directly. This method has a bias of approximately −10%, precision of approximately 60%. The fraction of estimates below an absolute error of 25% is 43%. These results support use of M2 to estimate CYP2A6 activity in smokers in the clinical setting.

Gene-gene interactions between CYP2B6 and CYP2A6 in nicotine metabolism.

Abstract: ObjectivesCYP2A6 is the major enzyme involved in nicotine metabolism, yet large interindividual variations in the rate of nicotine metabolism exist within groups of individuals having the same CYP2A6 genotype. We investigated the influence of genetic variation in another potential nicotine-metaboliz

The variability of urinary cotinine levels in young children: implications for measuring ETS exposure.

Abstract: This study examined the within-subject variability of urinary cotinine levels in young children (aged = 0.6-7.2 years) of smoking parents to determine the number of urine samples needed to provide accurate estimates of exposure to environmental tobacco smoke (ETS) for different time intervals. Secondary analyses were conducted of five independent studies (N = 376), in which multiple urinary cotinine measures had been collected over time periods up to 13 months. Over measurement periods of 4-15 days, the within-subject cotinine levels varied 3-5 times more than would be expected based on measurement error alone. Over 7-13 months, the within-subject variability was 10-20 times higher than would be expected based on the measurement error. Findings indicated that cotinine measures from single urine samples provided highly accurate estimates of only recent exposure (i.e., 2-3 days; rho = 0.99). To achieve similarly precise estimates of the mean cotinine level of an individual child over 4-15 days, up to nine urine samples may be necessary. Up to 12 urine samples may be required to achieve similarly precise estimates of ETS exposure over a 4- to 13-month period. Epidemiologic and clinical research on ETS exposure in children can benefit from multiple urine samples (a) to accurately measure average exposure at the level of the individual child, (b) to describe temporal patterns, (c) to detect incidences of peak exposure that would remain underrecognized if monitoring is limited to a single time point, and (d) to establish stable baseline levels and endpoints based on urine samples collected over clinically relevant time periods.

Relationship of Human Toenail Nicotine, Cotinine, and 4-(Methylnitrosamino)-1-(3-Pyridyl)-1-Butanol to Levels of These Biomarkers in Plasma and Urine

Abstract: Recently, we developed sensitive and quantitative methods for analysis of the biomarkers of tobacco smoke exposure nicotine, cotinine, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) in human toenails. In this study, we further evaluated the newly developed toenail biomarkers by investigating their relationship to demographic factors, reported exposure, plasma nicotine, cotinine, and trans-3'-hydroxycotinine, and urinary NNAL. Toenails of 105 smokers, mean age 38.9 years (range, 19-68), were analyzed. Fifty-five (53.4%) were male, with approximately equal numbers of Whites and African-Americans. The average number of cigarettes smoked per day was 18 (range, 5-50). There was no effect of age or gender on the toenail biomarkers. Toenail NNAL was higher in White than in African-American participants (P = 0.019). Toenail nicotine and toenail cotinine correlated significantly with cigarettes smoked per day (r = 0.24; P = 0.015 and r = 0.26; P = 0.009, respectively). Toenail nicotine correlated with plasma nicotine (r = 0.39; P < 0.001); toenail cotinine correlated with plasma cotinine (r = 0.45; P < 0.001) and plasma trans-3'-hydroxycotinine (r = 0.30; P = 0.008); and toenail NNAL correlated with urine NNAL (r = 0.53; P = 0.005). The results of this study provide essential validation data for the use of toenail biomarkers in investigations of the role of chronic tobacco smoke exposure in human cancer.

Determinants of salivary cotinine level: a population- based study in Brazil Determinantes dos níveis de cotinina salivar: um estudo de base populacional no Brasil

Abstract: 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 fi tting technique of robust locally weighted regression. RESULTS: Signifi cantly (p 40 ng/mL per cigarette were excluded. CONCLUSIONS: There was found a positive association between selfreporting smoking fi ve 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.

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

Abstract: OBJETIVO: Realizou-se um estudo transversal para analisar a relacao entre numero de cigarros fumados e outras caracteristicas com a concentracao de cotinina salivar entre fumantes. METODOS: Fumantes ativos de 15 anos ou mais foram selecionados por meio de amostra probabilistica em multiplos estagios no ano 2000, municipio do Rio de Janeiro, Brasil. O estudo incluiu 401 fumantes. A concentracao de cotinina salivar foi determinada utilizando-se cromatografia gasosa com detector de nitrogenio/fosforo. Coletaram-se informacoes demograficas e sobre o comportamento tabagico utilizando-se questionario padronizado. A relacao entre o numero de cigarros fumados nas ultimas 24h e o nivel de cotinina foi analisada utilizando tecnica nao parametrica baseada em regressoes robustas locais ponderadas. RESULTADOS: O nivel medio ajustado de cotinina foi significativamente (p<0,05) mais elevado entre individuos que fumaram o primeiro cigarro ate cinco minutos depois de acordar e entre os que fumaram de um a 20 cigarros nas ultimas 24h e tragavam mais de metade das vezes. Considerando-se fumantes de um a 20 cigarros, a inclinacao da curva de regressao foi significativamente maior entre os que, apos acordar, esperam mais de cinco minutos para fumar e para os que consumiam cigarros "suaves", quando comparados a seus opostos. Essas heterogeneidades desaparecem ao se excluir individuos com cotinina inferior a 40 ng/ml/cigarro. CONCLUSOES: Houve associacao positiva entre referir fumar ate cinco minutos depois de acordar e tragar mais da metade das vezes e niveis de cotinina salivar. Essas informacoes podem ser marcadores de dependencia e maior absorcao de nicotina entre fumantes. A cotinina salivar mostrou-se util como biomarcador do uso recente de tabaco a ser usado em estudos epidemiologicos e programas de cessacao de fumar.

Modeling the relationship of cotinine and self-reported measures of maternal smoking during pregnancy : A deterministic approach

Abstract: Studies of effects of prenatal exposure to cigarettes frequently acquire both self-report and biological assays of maternal smoking. However, little attention has been paid to methods for combining information from both sources to enhance the precision of exposure measurement. This paper analyzes the relationship between the two commonly used measures of smoking exposure during pregnancy: Maternal self-report and urinary cotinine. We present a deterministic method for combining the two measures and examine its robustness under different assumptions. We apply the method to a dataset from the Family Health and Development Project. In addition, we propose an approach for calibrating the self-report measures for individual women based on both sources of information. Enhancing the quality of exposure measurement may substantially advance studies of the teratological effects of exposure on offspring.

Genetic and Environmental Sources of Variation in Heart Rate Response to Infused Nicotine in Twins

Abstract: The heart rate response to nicotine may be an important component of the process leading to dependence. The present study is the first to determine the extent to which genetic and environmental sources play a role in various components of the heart rate response. One hundred and ten monozygotic and 29 dizygotic twin pairs received an i.v. infusion of nicotine and cotinine over 30 min. Before, during, and for 30 min after infusion, heart rate was measured via an electronic monitor. The clearance of nicotine was determined as a measure of the rate of nicotine metabolism. Average resting heart rate before infusion was 64.7 beats per minutes (bpm), and at the termination of infusion, heart rate had increased to an average of 72.7 bpm. At 30 min after infusion, heart rate had decreased to 67.5 bpm. Age, current smoking status, body mass index, and nicotine clearance were associated significantly with heart rate levels over the full 60 min of measurement. After adjustment for several covariates, including dose of administered nicotine and rate of nicotine clearance, the variance in several characteristics of the heart rate response curve was examined for the relative contribution from genetic and environmental sources. In the total sample, as much as 30.3% of the variance in the acceleration of heart rate was due to additive genetic sources. In nonsmokers, 34.8% and 31.0% of variance in the acceleration and deceleration of heart rate, respectively, was due to genetic sources. Heart rate acceleration and deceleration may be a reflection of central nervous system responsiveness to nicotine. The contribution from genetic sources to heart rate response characteristics should be investigated further as a potential endophenotype for use in genetic studies of nicotine dependence.

Population pharmacokinetics of nicotine and its metabolites I. Model development.

Abstract: We present a mechanistic population model for the pharmacokinetics of nicotine (NIC), its primary (CYP2A6-generated) metabolite cotinine (COT), and COT’s primary (CYP2A6-generated) metabolite, trans-3′-hydroxycotinine (3HC). Sixty-six subjects received oral deuterium-labeled NIC (NIC-d2, 2 mg), and COT (COT-d4, 10 mg) simultaneously. Frequent plasma/saliva samples were taken for measurement of concentrations of NIC-d2, COT-d2, 3HC-d2, COT-d4, and 3HC-d4. A mechanistic population pharmacokinetic model was fitted to all data simultaneously. Most of the pharmacokinetic parameters found here agree with previous studies and with a previous model-independent analysis of these data. However, 3HC t1/2 was found to be considerably shorter than a previously reported value, possibly because 3HC elimination was saturated with the larger doses used in the previous study. Additionally, the delay in the appearance of COT-d2 in the blood was modeled as a time delay (t1/2 = 12 min) in its release from the liver following NIC-d2 administration. The most important result of the previous model-independent analysis of these data, confirmed here, is that NIC clearance to COT and the 3HC:COT saliva concentration ratio are highly correlated (r = 0.7−0.8). The correlation above support that idea that the 3HC:COT ratio can be used as a predictor of CYP2A6 activity and nicotine clearance. The model-based analysis extends and further justifies this conclusion.

Secondhand smoke exposure in Mexican discotheques.

Abstract: This study describes the impact of exposure to secondhand smoke for subjects who spend time in a discotheque, by comparing within-subject baseline and postexposure urinary cotinine levels A total of 100 nonsmoking volunteers from a central region of Mexico provided a urine sample before entering a discotheque and another sample an average of 6 hr after the end of exposure Concentrations of cotinine and its metabolite, trans-3'-hydroxycotinine, were measured in the urine by liquid chromatography-mass spectrometry In females the average preexposure level of urinary cotinine was 22 ng/ml, and the average postexposure level was significantly higher, at 157 ng/ml In males the average preexposure level of cotinine was 37 ng/ml, compared with 491 ng/ml in the postexposure assessment The highest postexposure values were found in men younger than 22 years old with a value of 4695 ng/ml Exposure to secondhand smoke is a serious health risk Our findings are important given that many of our subjects were exposed to substantial amounts of secondhand smoke in discotheques, as evidenced by the high urinary cotinine and 3'-hydroxycotinine concentrations These findings support the need to prohibit smoking in discotheques to protect nonsmokers' health

The Use of Hemodialysis and Hemoperfusion in the Treatment of Theophylline Intoxication

Abstract: Theophylline intoxication remains a major source of morbidity and mortality related to drug intoxication (1). The signs and symptoms of theophylline intoxication are summarized in Table 1. The primary causes of death or serious morbidity are sustained or recurrent seizures (often associated with hyperthermia) and cardiac arrhythmias (2, 3). Seizures are the most frequent life-threatening complication of theophylline intoxication. Death or permanent neurological injury occurs due to the combination of seizures, hypotension, and hyperthermia (4). To meet the increased metabolic demands, the seizing brain requires rates of blood flow that are several times greater than those required during the nonseizing state. During seizures, blood vessels in the brain dilate and, due to general sympathetic neural discharge, blood pressure increases. Cerebral blood flow increases in proportion to the increase in mean arterial blood pressure to match the metabolic demands of the brain. Hypotension produced by theophylline (primarily by systemic arterial vasodilation) limits the homeostatic increase in cerebral blood flow. Hyperthermia, occurring as a result of heat generated by muscular hyperactivity during seizures, further increases the metabolic requirements of the brain and aggravates the imbalance between nutrient supply and demand. In one series of 12 patients with drug-

Nicotine, cotinine, withdrawal, and craving patterns during smoking and nicotine nasal spray use: results from a pilot study with African American men.

Abstract: Nicotine intake via smoking is highly variable. Individualized dosing of nicotine replacement therapy (NRT) may improve product efficacy, but a better understanding of the within-day and within-subject relationships between smoking, NRT use, nicotine and cotinine concentrations in blood, and cravings and withdrawal symptoms is needed to inform dosing algorithms. A pilot study was undertaken to collect data on these relationships and to assess the feasibility of the methods needed for this type of research, including a sophisticated statistical modeling technique (a two-part mixed-effects model with correlated random effects that accounts for clumping at zero). Because nicotine metabolism varies by gender and race, the sample was homogeneous with respect to these characteristics. In a within-subjects study, 27 African American adult male smokers carried a computerized cigarette dispenser for 1 week, capturing the time each cigarette was smoked. Subjects then entered an inpatient setting for 1 day of scheduled smoking (matched to data from the cigarette dispenser to create an ecologically valid schedule) and 4 days of ad libitum nicotine nasal spray use, while tobacco abstinent. Eight times per day, at 2-hour intervals, blood was drawn and ratings of cigarette cravings and withdrawal symptoms were obtained. On average, subjects used less than half of the manufacturer's recommended minimum daily dose of nicotine nasal spray. Large differences in nicotine and cotinine levels were observed between individuals. When predicting nicotine, cotinine, withdrawal, and cravings, we observed significant interactions between route of nicotine intake and a variety of independent variables.

Genetic nondiscrimination legislation: a critical prerequisite for pharmacogenomics data sharing

Abstract: Russ B Altman1†, Neal Benowitz2, David Gurwitz3, Jeantine Lunshof4, Mary Relling5, Jatinder Lamba5, Eric Wieben6, Sean Mooney7, Kathleen Giacomini2, Scott Weiss8, Julie A Johnson9, Howard McLeod10, David Flockhart7, Richard Weinshilboum6, Alan R Shuldiner11, Dan Roden12, Ronald M Krauss13 & Mark Ratain14 †Author for correspondence 1Stanford University, Department of Genetics and Bioengineering, Clark S172, Stanford, CA 94305-5444, USA E-mail: Russ.Altman@ stanford.edu 2University of California, San Francisco 3Tel-Aviv University 4VU University Medical Center 5St Jude Children’s Research Hospital 6Mayo Clinic 7Indiana University School of Medicine 8Harvard Medical School 9University of Florida 10University of North Carolina 11University of Maryland 12Vanderbilt School of Medicine 13Children’s Hospital Oakland Research Institute 14University of Chicago On 31st January 2007, the US Senate Health, Education, Labor and Pensions Committee approved the Genetic Information Nondiscrimination Act (GINA) by a vote of 19:2. It was unanimously approved by the US Congress Committee on Education and Labor 2 weeks later. This legislation, aimed at preventing genetic discrimination in employment and insurance [1], will be imperative for protecting altruistic individuals who volunteer for genetic research [2]. There is an emerging consensus among researchers that genetic data must be accessible to individual research participants upon their request [3], while not putting them at risk with respect to their employment, insurance and additional personal aspects [4]. The GINA balances individual freedoms and privacy rights with societal needs for affordable and more effective healthcare and helps to pave the way for more personalized medicine [5]. Indeed, genetic information can be used to improve healthcare, in particular with regard to reducing the alarming rates of adverse drug reactions, which led to 6.7% of all US hospital admissions during 2004–2005 [6], consistent with earlier studies in the UK [7]. Increased use of individual genetic information about drug-metabolizing and drug-target gene alleles as part of healthcare treatment decisions may substantially reduce such morbidity [8]. However, building up the required knowledge depends on the analysis of large individual genotype/phenotype data sets from patient cohorts and requires open data sharing so that large, meaningful and less biased data sets are available to researchers [9]. Lack of open data sharing, in particular between the private and public sectors, hinders our ability to assemble large aggregated data sets [9]. A key obstacle for data sharing is concern about depositing data sets from individual study participants into public databases; some researchers fear they will be held responsible in cases where the data are re-identified (using computational data-mining techniques) and subsequently used (by employers or insurers) to discriminate against study participants. We therefore believe that legislation that offers protection to individuals or groups who share genetic information – against both re-identification and discrimination – is essential for efforts to move genomic medicine into practice. Legislation barring discrimination or stigmatization based on genetic information has been proposed for years, but enactment has become particularly urgent in view of rapidly falling genotyping costs [10], the scope of ongoing genome-wide association studies [11] and the increasing availability of comprehensive personal data in the public domain [4]. We therefore strongly support the current efforts to establish a solid legal framework as a primary means to protect individuals against misuse of their genetic information and as an essential tool for allowing open data sharing in pharmacogenomics.

Cigarette smoking and the personalization of irinotecan therapy.

Abstract: Lifelong cigarette smokers have a 50% chance of dying prematurely due to their addiction. Nearly one third of these deaths are due to cancer. Smokers who develop cancer are often highly addicted and many continue to smoke after the diagnosis of cancer. Smoking-induced cancers that are treated with irinotecan include colon cancer, lung cancer, and others. Irinotecan is a topoisomerase I inhibitor, with dose-limiting toxicity that includes leukopenia and severe diarrhea. Irinotecan is a prodrug, which is metabolized primarily by carboxylesterase enzymes to an active metabolite, 7-ethyl-10-hydroxycamptothecin (SN-38). Irinotecan is also metabolized by the enzyme CYP3A4, and one of the metabolites via the CYPA4 pathway can be metabolized further by carboxylesterase to SN-38. SN-38 is in turn detoxified by glucuronide conjugation via the enzyme uridine diphosphate glucuronosyltransferase (UGT) 1A1. The disposition kinetics and related safety and efficacy of irinotecan are influenced to a considerable degree by genetic and environmental factors. A variant genotype in the promoter region of the UGT enzyme, UGT1A1*28, is associated with a remarkably reduced rate of SN-38 glucuronidation, and a higher risk of irinotecan toxicity with standard dosing. This variant also causes the Gilbert syndrome. Clinical diagnostic tests for the UGT1A1*28 variant have been developed and promoted as a way to individualize irinotecan dosing and to prevent serious toxicity. Environmental factors such as the use of other drugs and cigarette smoking also influence response to irinotecan. Antiepileptic drugs such as phenytoin and carbamazepine accelerate irinotecan and SN-38 metabolism substantially, resulting in decreased levels of SN-38. As a consequence, higher doses of irinotecan are recommended in patients receiving antiepileptic drugs as part of treatment of malignant glioma. Another major environmental modulator of irinotecan response, cigarettes smoking, has been shown to decrease the risk of hematologic toxicity from irinotecan, as described by van der Bol et al in this issue. The risk of irinotecan-induced neutropenia in this study was 6% for smokers compared with 38% for nonsmokers. There was a trend toward a lesser incidence of delayed-onset diarrhea (6% v 15%), but this difference was not significant. Cigarette smoking is well known to interact with a variety of drugs, both by pharmacokinetic and pharmacodynamic mechanisms. Pharmacokinetic interactions are related primarily to the effects of cigarette smoking to induce many drug-metabolizing enzymes and to inhibit some drug-metabolizing enzymes. Polycyclic aromatic hydrocarbons in cigarette smoke are responsible for the induction of lung and liver enzymes, including CYP1A1 and CYP1A2. Smoking-induced induction of CYP1A2 accounts for well-known interactions of smoking with drugs such as caffeine, clozapine, haloperidol, fluvoxamine, olanzapine, tacrine, and theophylline. Recently, smoking has been shown to accelerate the metabolism of erlotinib, another drug metabolized by CYP1A1 and 1A2, which likely explains the poorer response of smokers compared with nonsmokers with non–small-cell lung cancer. Cigarette smoking also induces the enzyme CYP2E1 and inhibits CYP2A6, effects that may be mediated by nicotine. There are conflicting data on the effects of cigarette smoking on the induction of CYP3A4. Cigarette smoking also induces the glucuronidation of some drugs, including mexiletine, propranolol, and codeine, although interestingly in the context of the present study, not morphine or bilirubin. Cigarette smoking has many other physiologic effects that could affect drug response, including effects on the hematopoietic system, including an increase in neutrophil count. Smoking seems to stimulate the bone marrow by releasing proinflammatory factors from macrophages. A direct effect of cigarette smoking on neutrophil count must be considered as a possible mechanism by which smoking reduces neutropenia due to irinotecan. The article by van der Bol et al explores the mechanism of the smoking effect on irinotecan toxicity. Key observations in smokers include lower levels of irinotecan and SN-38 in the plasma, and no significant change in SN-38 glucuronide levels. As an important control, UGT1A1*28 genotype prevalence was not different in smokers versus nonsmokers, eliminating genetic predisposition as a confounder for differential risk of toxicity. The data in this article suggest that cigarette smoking accelerates the metabolism of irinotecan to SN-38, and based on the higher ratios of SN-38 glucuronide to SN-38, also accelerates the glucuronidation of SN-38. Given that the levels of SN-38 were substantially lower in smokers compared with those in nonsmokers, the effects of smoking to induce SN-38 glucuronidation seem to far exceed the effects of smoking to accelerate the conversion of irinotecan to SN-38. As the authors of this informative study mention, although cigarette smoking may reduce the toxicity of irinotecan, it does so by lowering the levels of the active metabolite SN-38. Lower levels of circulating SN-38 might be expected to reduce the therapeutic JOURNAL OF CLINICAL ONCOLOGY E D I T O R I A L VOLUME 25 NUMBER 19 JULY 1 2007