The kinetics of ethanol absorption and elimination in twins and supplementary repetitive experiments in singleton subjects

Genetic variants in ALDH1B1 and alcohol dependence risk in a British and Irish population: A bioinformatic and genetic study

Alcohol is metabolized in the liver via the enzymes alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). Polymorphisms in the genes encoding these enzymes, which are common in East Asian populations, can alter enzyme kinetics and hence the risk of alcohol dependence and its sequelae. One of the most important genetic variants, in this regards, is the single nucleotide polymorphism (SNP) rs671 in ALDH2, the gene encoding the primary acetaldehyde metabolizing enzyme ALDH2. However, the protective allele of rs671 is absent in most Europeans although ALDH1B1, which shares significant sequence homology with ALDH2, contains several, potentially functional, missense SNPs that do occur in European populations. The aims of this study were: (i) to use bioinformatic techniques to characterize the possible effects of selected variants in ALDH1B1 on protein structure and function; and, (ii) to genotype three missense and one stop-gain, protein-altering, non-synonymous SNPs in 1478 alcohol dependent cases and 1254 controls of matched British and Irish ancestry. No significant allelic associations were observed between the three missense SNPs and alcohol dependence risk. The minor allele frequency of rs142427338 (Gln378Ter) was higher in alcohol dependent cases than in controls (allelic P = 0.19, OR = 2.98, [0.62–14.37]) but as this SNP is very rare the study was likely underpowered to detect an association with alcohol dependence risk. This potential association will needs to be further evaluated in other large, independent European populations.

The Role of CYP2E1 in the Drug Metabolism or Bioactivation in the Brain

Organisms have metabolic pathways that are responsible for removing toxic agents. We always associate the liver as the major organ responsible for detoxification of the body; however this process occurs in many tissues. In the same way, as in the liver, the brain expresses metabolic pathways associated with the elimination of xenobiotics. Besides the detoxifying role of CYP2E1 for compounds such as electrophilic agents, reactive oxygen species, free radical products, and the bioactivation of xenobiotics, CYP2E1 is also related in several diseases and pathophysiological conditions. In this review, we describe the presence of phase I monooxygenase CYP2E1 in regions of the brain. We also explore the conditions where protein, mRNA, and the activity of CYP2E1 are induced. Finally, we describe the relation of CYP2E1 in brain disorders, including the behavioral relations for alcohol consumption via CYP2E1 metabolism.

Genetic variants in or near ADH1B and ADH1C affect susceptibility to alcohol dependence in a British and Irish population

Certain single nucleotide polymorphisms (SNPs) in genes encoding alcohol dehydrogenase (ADH) enzymes confer a significant protective effect against alcohol dependence syndrome (ADS) in East Asian populations. Recently, attention has focused on the role of these SNPs in determining ADS risk in European populations. To further elucidate these associations, SNPs of interest in ADH1B, ADH1C and the ADH1B/1C intergenic region were genotyped in a British and Irish population (ADS cases n = 1076: controls n = 1027) to assess their relative contribution to ADS risk. A highly significant, protective association was observed between the minor allele of rs1229984 in ADH1B and ADS risk [allelic P = 8.4 × 10(-6) , odds ratio (OR) = 0.26, 95 percent confidence interval, 0.14, 0.49]. Significant associations were also observed between ADS risk and the ADH1B/1C intergenic variant, rs1789891 [allelic P = 7.2 × 10(-5) , OR = 1.4 (1.2, 1.6)] and three non-synonymous SNPs rs698, rs1693482 and rs283413 in ADH1C. However, these associations were not completely independent; thus, while the ADH1B rs1229984 minor allele association was independent of those of the intergenic variant rs1789891 and the three ADH1C variants, the three ADH1C variants were not individually independent. In conclusion, the rare ADH1B rs1229984 mutation provides significant protection against ADS in this British and Irish population; other variants in the ADH gene cluster also alter ADS risk, although the strong linkage disequilibrium between SNPs at this location precluded clear identification of the variant(s) driving the associations.

β-Lapachone alleviates alcoholic fatty liver disease in rats

Alcohol-induced liver injury is the most common liver disease in which fatty acid metabolism is altered. It is thought that altered NAD(+)/NADH redox potential by alcohol in the liver causes fatty liver by inhibiting fatty acid oxidation and the activity of tricarboxylic acid cycle reactions. β-Lapachone (βL), a naturally occurring quinone, has been shown to stimulate fatty acid oxidation in an obese mouse model by activating adenosine monophosphate-activated protein kinase (AMPK). In this report, we clearly show that βL reduced alcohol-induced hepatic steatosis and induced fatty acid oxidizing capacity in ethanol-fed rats. βL treatment markedly decreased hepatic lipids while serum levels of lipids and lipoproteins were increased in rats fed ethanol-containing liquid diets with βL administration. Furthermore, inhibition of lipolysis, enhancement of lipid mobilization to mitochondria and upregulation of mitochondrial β-oxidation activity in the soleus muscle were observed in ethanol/βL-treated animals compared to the ethanol-fed rats. In addition, the activity of alcohol dehydrogenase, but not aldehyde dehydrogenase, was significantly increased in rats fed βL diets. βL-mediated modulation of NAD(+)/NADH ratio led to the activation of AMPK signaling in these animals.

CONCLUSION

Our results suggest that improvement of fatty liver by βL administration is mediated by the upregulation of apoB100 synthesis and lipid mobilization from the liver as well as the direct involvement of βL on NAD(+)/NADH ratio changes, resulting in the activation of AMPK signaling and PPARα-mediated β-oxidation. Therefore, βL-mediated alteration of NAD(+)/NADH redox potential may be of potential therapeutic benefit in the clinical setting.

Association between in vivo alcohol metabolism and genetic variation in pathways that metabolize the carbon skeleton of ethanol and NADH reoxidation in the alcohol challenge twin study

BACKGROUND

Variation in alcohol metabolism affects the duration of intoxication and alcohol use. While the majority of genetic association studies investigating variation in alcohol metabolism have focused on polymorphisms in alcohol or aldehyde dehydrogenases, we have now tested for association with genes in alternative metabolic pathways that catalyze the carbon skeleton of ethanol (EtOH) and NADH reoxidation.

METHODS

Nine hundred fifty single nucleotide polymorphisms (SNPs) spanning 14 genes (ACN9, ACSS1, ACSS2, ALDH1A1, CAT, CYP2E1, GOT1, GOT2, MDH1, MDH2, SLC25A10, SLC25A11, SLC25A12, SLC25A13) were genotyped in 352 young adults who participated in an alcohol challenge study. Traits tested were blood alcohol concentration (BAC), breath alcohol concentration (BrAC), peak alcohol concentration, and rates of alcohol absorption and elimination. Allelic association was tested using quantitative univariate and multivariate methods.

RESULTS

A CYP2E1 promoter SNP (rs4838767, minor allele frequency 0.008) exceeded the threshold for study-wide significance (4.01 × 10(-5) ) for 2 early BAC, 8 BrAC measures, and the peak BrAC. For each phenotype, the minor C allele was related to a lower alcohol concentration, most strongly for the fourth BrAC (p = 2.07 × 10(-7) ) explaining ~8% of the phenotypic variance. We also observed suggestive patterns of association with variants in ALDH1A1 and on chromosome 17 near SLC25A11 for aspects of blood and breath alcohol metabolism. An SNP upstream of GOT1 (rs2490286) reached study-wide significance for multivariate BAC metabolism (p = 0.000040).

CONCLUSIONS

Overall, we did not find strong evidence that variation in genes coding for proteins that further metabolize the carbon backbone of acetaldehyde, or contribute to mechanisms for regenerating NAD from NADH, affects alcohol metabolism in our European-descent subjects. However, based on the breath alcohol data, variation in the promoter of CYP2E1 may play a role in preabsorptive or early hepatic alcohol metabolism, but more samples are required to validate this finding.

ADH single nucleotide polymorphism associations with alcohol metabolism in vivo

We have previously found that variation in alcohol metabolism in Europeans is linked to the chromosome 4q region containing the ADH gene family. We have now typed 103 single nucleotide polymorphisms (SNPs) across this region to test for allelic associations with variation in blood and breath alcohol concentrations after an alcohol challenge. In vivo alcohol metabolism was modelled with three parameters that identified the absorption and rise of alcohol concentration following ingestion, and the rate of elimination. Alleles of ADH7 SNPs were associated with the early stages of alcohol metabolism, with additional effects in the ADH1A, ADH1B and ADH4 regions. Rate of elimination was associated with SNPs in the intragenic region between ADH7 and ADH1C, and across ADH1C and ADH1B. SNPs affecting alcohol metabolism did not correspond to those reported to affect alcohol dependence or alcohol-related disease. The combined SNP associations with early- and late-stage metabolism only account for approximately 20% of the total genetic variance linked to the ADH region, and most of the variance for in vivo alcohol metabolism linked to this region is yet to be explained.

A haplotype analysis of CYP2E1 polymorphisms in relation to alcoholic phenotypes in Mexican Americans

BACKGROUND

Studies regarding the association between the 4 polymorphisms of CYP2E1 (CYP2E1*1D, *5B, *6, and *1B) and alcoholism are inconsistent and inconclusive. The purpose of the present study was to clarify previously discordant studies by haplotype analysis in the Mexican American population.

METHODS

The 4 polymorphisms of CYP2E1 were studied in 334 alcoholics and 365 controls. Genotype, allele, and haplotype frequency comparisons between alcoholics and controls were assessed. Patterns of linkage disequilibrium (LD) at CYP2E1 were determined. Reconstructed haplotypes were tested for associations with clinical phenotypes (age onset of drinking, Maxdrinks, and smoking status).

RESULTS

No significant associations between the 4 polymorphisms of CYP2E1 and alcoholism were revealed by single allele tests. High LD was found between the CYP2E1 c2 and C alleles in Mexican Americans. Eleven haplotypes were present in the 699 participants. The 6 main haplotypes with frequencies higher than 1% made up 97% of the total halpotypes. The frequency of subjects carrying H6 (1C-c2-C-A2) was significantly higher in alcoholics than in controls (p = 0.0001). In contrast, the frequencies of H7 (1C-c2-C-A1) and H10 (1C-c2-D-A1) were significantly lower in alcoholics than in controls (p = 0.0072 for H7 and p = 0.0407 for H10). The frequency of H6 was significantly higher in alcoholics who had late onset of drinking than in nonalcoholic controls. Furthermore, the frequencies of H6 haplotype were also consistently higher in groups who had high number of maximum drinks (9 to 32 drinks) than in controls. When smokers are excluded, the frequencies of H6, H7, and H9 (1C-c2-D-A2) showed statistically significant differences between alcoholics and controls (p < 0.05). Moreover, the association between H6 and alcoholism become more robust when smokers are excluded. Furthermore, the frequency of H1 (1C-c1-D-A2) in alcoholic-smokers was much higher than in alcoholic-nonsmokers (p = 0.0028). In contrast, alcoholic-smokers carried less H2 (1C-c1-D-A1) in comparison with alcoholic-nonsmokers (p = 0.0417). The H3 (1D-c2-C-A2) frequency in alcoholic-smokers was much lower than in alcoholic-nonsmokers (p = 0.0042) and control-smokers (p = 0.0363).

CONCLUSIONS

Our data demonstrate that carrying haplotype H6 might enhance susceptibility to developing alcoholism, but possessing the H7 or H10 haplotype appears to decrease this susceptibility. The H6, H7, and H9 haplotypes may play certain roles in different clinical phenotypes in Mexican American alcoholics. In addition, our data suggest that the H1, H2, and H3 haplotypes are associated with alcohol drinking and smoking. These results support that haplotype analysis is much more informative than single allele analysis. Our findings clearly indicate the importance of H6 haplotype in alcohol drinking in Mexican Americans.

Overview of the role of alcohol dehydrogenase and aldehyde dehydrogenase and their variants in the genesis of alcohol-related pathology

Alcohol dehydrogenase (ADH) and mitochondrial aldehyde dehydrogenase (ALDH2) are responsible for metabolizing the bulk of ethanol consumed as part of the diet and their activities contribute to the rate of ethanol elimination from the blood. They are expressed at highest levels in liver, but at lower levels in many tissues. This pathway probably evolved as a detoxification mechanism for environmental alcohols. However, with the consumption of large amounts of ethanol, the oxidation of ethanol can become a major energy source and, particularly in the liver, interferes with the metabolism of other nutrients. Polymorphic variants of the genes for these enzymes encode enzymes with altered kinetic properties. The pathophysiological effects of these variants may be mediated by accumulation of acetaldehyde; high-activity ADH variants are predicted to increase the rate of acetaldehyde generation, while the low-activity ALDH2 variant is associated with an inability to metabolize this compound. The effects of acetaldehyde may be expressed either in the cells generating it, or by delivery of acetaldehyde to various tissues by the bloodstream or even saliva. Inheritance of the high-activity ADH β2, encoded by theADH2*2gene, and the inactiveALDH2*2gene product have been conclusively associated with reduced risk of alcoholism. This association is influenced by gene–environment interactions, such as religion and national origin. The variants have also been studied for association with alcoholic liver disease, cancer, fetal alcohol syndrome, CVD, gout, asthma and clearance of xenobiotics. The strongest correlations found to date have been those between theALDH2*2allele and cancers of the oro-pharynx and oesophagus. It will be important to replicate other interesting associations between these variants and other cancers and heart disease, and to determine the biochemical mechanisms underlying the associations.

In Vivo and in Vitro Characterization of Chlorzoxazone Metabolism and Hepatic CYP2E1 Levels in African Green Monkeys: Induction by Chronic Nicotine Treatment

CYP2E1 metabolizes compounds, including clinical drugs, organic solvents, and tobacco-specific carcinogens. Chlorzoxazone (CZN) is a probe drug used to phenotype for CYP2E1 activity. Smokers have increased CZN clearance during smoking compared with nonsmoking periods; however, it is unclear which cigarette smoke component is causing the increased activity. The relationships between in vivo CZN disposition, in vitro CZN metabolism, and hepatic CYP2E1 have not been investigated in a within-animal design. In control-treated monkeys (Cercopithecus aethiops), the in vivo CZN area under the curve extrapolated to infinity (AUC(inf)) was 19.7 +/- 4.5 microg x h/ml, t1/2 was 0.57 +/- 0.07 h, and terminal disposition rate constant calculated from last three to four points on the log-linear end of the concentration versus time curve was 1.2 +/- 0.2 /h. In vitro, the apparent Vmax was 3.48 +/- 0.02 pmol/min/mug microsomal protein, and the Km was 95.4 +/- 1.8 microM. Chronic nicotine treatment increased in vivo CZN disposition, as indicated by a 52% decrease in AUC(inf) (p < 0.01) and 52% decrease in Tmax (p < 0.05) compared with control-treated monkeys. The log metabolic ratios at 0.5, 1, 2, and 4 h significantly negatively correlated with CZN AUC(inf) (p = 0.01-0.0001). Monkey hepatic CYP2E1 levels significantly correlated with both in vivo AUC(inf) (p = 0.03) and in vitro (p = 0.004) CZN metabolism. Together, the data indicated that nicotine induction of in vivo CZN disposition is related to the rates of in vitro CZN metabolism and hepatic microsomal CYP2E1 protein levels. Nicotine is one component in cigarette smoke that can increase in vivo CZN metabolism via induction of hepatic CYP2E1 levels. Thus, nicotine exposure may affect the metabolism of CYP2E1 substrates such as acetaminophen, ethanol, and benzene.

Liver enzyme induction and inhibition: implications for anaesthesia

Recent breakthroughs in molecular biology have enabled a reclassification of drug metabolising enzymes based on their amino acid sequence. This has led to a better understanding of drug metabolism and drug interactions. The majority of these drug metabolising enzymes may be either induced or inhibited by drugs or by extraneous substances including foodstuffs, cigarette smoke and environmental pollutants. Virtually all drugs used in anaesthesia are metabolised by either hepatic phase 1 or phase II enzymes. This review considers the classification of drug metabolising enzymes, explains the mechanisms of enzyme induction and inhibition, and also considers how the action of drugs commonly used by anaesthetists, including opioids and neuromuscular blocking drugs, may be altered by this mechanism.

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.

The Unique Regulation of Brain Cytochrome P450 2 (CYP2) Family Enzymes by Drugs and Genetics

Cytochrome P450 (CYP) enzymes in the brain may have a role in the activation or inactivation of centrally acting drugs, in the metabolism of endogenous compounds, and in the generation of damaging toxic metabolites and/or oxygen stress. CYPs are distributed unevenly among brain regions, and are found in neurons, glial cells and at the blood-brain interface. They have been observed in mitochondrial membranes, in neuronal processes and in the plasma membrane, as well as in endoplastic reticulum. Brain CYPs are inducible by many common hepatic inducers, however many compounds affect liver and brain CYP expression differently, and some CYPs which are constitutively expressed in liver are inducible in brain. CYP induction is isozyme-, brain region-, cell type- and inducer-specific. While it is unlikely that brain CYPs contribute to overall clearance of xenobiotics, their punctate, region- and cell-specific expression suggests that CNS CYPs may create micro-environments in the brain with differing drug and metabolite levels (not detected or predicted by plasma drug monitoring). Coupled with the sensitivity of CNS CYPs to induction, this may in part account for inter-individual variation in response to centrally acting drugs and neurotoxins, and may have implications for individual variation in receptor adaptation and cross-tolerance to different drugs. In addition, genetic variation in brain CYPs, depending on the type of polymorphism (structural versus regulatory), will alter enzyme activity. These aspects of brain CYP expression regulation and genetic influences are illustrated in this review using mRNA, protein, and enzyme activity data for CYP2D1/6, CYP2E1 and CYP2B1/6 in rat and human brain. The role of CYP-mediated metabolism in the brain, a highly heterogeneous and complex organ, is a new and relatively unexplored field of scientific enquiry. It holds promise for furthering our undestanding of inter-individual variability in response to centrally acting drugs as well as risk for neurological diseases and pathogies.

Role of variability in explaining ethanol pharmacokinetics: research and forensic applications

Variability in the rate and extent of absorption, distribution and elimination of ethanol has important ramifications in clinical and legal medicine. The speed of absorption of ethanol from the gut depends on time of day, drinking pattern, dosage form, concentration of ethanol in the beverage, and particularly the fed or fasting state of the individual. During the absorption phase, a concentration gradient exists between the stomach, portal vein and the peripheral venous circulation. First-pass metabolism and bioavailability are difficult to assess because of dose-, time- and flow-dependent kinetics. Ethanol is transported by the bloodstream to all parts of the body. The rate of equilibration is governed by the ratio of blood flow to tissue mass. Arterial and venous concentrations differ as a function of time after drinking. Ethanol has low solubility in lipids and does not bind to plasma proteins, so volume of distribution is closely related to the amount of water in the body, contributing to sex- and age-related differences in disposition. The bulk of ethanol ingested (95-98%) is metabolised and the remainder is excreted in breath, urine and sweat. The rate-limiting step in oxidation is conversion of ethanol into acetaldehyde by cytosolic alcohol dehydrogenase (ADH), which has a low Michaelis-Menten constant (Km) of 0.05-0.1 g/L. Moreover, this enzyme displays polymorphism, which accounts for racial and ethnic variations in pharmacokinetics. When a moderate dose is ingested, zero-order elimination operates for a large part of the blood-concentration time course, since ADH quickly becomes saturated. Another ethanol-metabolising enzyme, cytochrome P450 2E1, has a higher Km (0.5-0.8 g/L) and is also inducible, so that the clearance of ethanol is increased in heavy drinkers. Study design influences variability in blood ethanol pharmacokinetics. Oral or intravenous administration, or fed or fasted state, might require different pharmacokinetic models. Recent work supports the need for multicompartment models to describe the disposition of ethanol instead of the traditional one-compartment model with zero-order elimination. Moreover, appropriate statistical analysis is needed to isolate between- and within-subject components of variation. Samples at low blood ethanol concentrations improve the estimation of parameters and reduce variability. Variability in ethanol pharmacokinetics stems from a combination of both genetic and environmental factors, and also from the nonlinear nature of ethanol disposition, experimental design, subject selection strategy and dose dependency. More work is needed to document variability in ethanol pharmacokinetics in real-world situations.

Brain CYP2E1 is induced by nicotine and ethanol in rat and is higher in smokers and alcoholics

1. Ethanol and nicotine are commonly coabused drugs. Cytochrome P450 2E1 (CYP2E1) metabolizes ethanol and bioactivates tobacco-derived procarcinogens. Ethanol and nicotine can induce hepatic CYP2E1 and we hypothesized that both centrally active drugs could also induce CYP2E1 within the brain. 2. Male rats were treated with saline, ethanol (3.0 g kg(-1) by gavage) or nicotine (1.0 mg kg(-1) s.c.) for 7 days. Ethanol treatment significantly increased CYP2E1 in olfactory bulbs (1.7-fold), frontal cortex (2.0-fold), hippocampus (1.9-fold) and cerebellum (1.8-fold), while nicotine induced CYP2E1 in olfactory bulbs (2.3-fold), frontal cortex (3.0-fold), olfactory tubercle (3.1-fold), cerebellum (2.5-fold) and brainstem (2.0-fold). Immunocytochemical analysis revealed that the induction was cell-type specific. 3. Consistent with the increased CYP2E1 found in rat brain following drug treatments, brains from alcoholics and alcoholic smokers showed greater staining of granular cells of the dentate gyrus and the pyramidal cells of CA2 and CA3 hippocampal regions as well as of cerebellar Purkinje cells compared to nonalcoholic nonsmokers. Moreover, greater CYP2E1 immunoreactivity was observed in the frontal cortices in the alcoholic smokers in comparison to nonalcoholic nonsmokers and alcoholic nonsmokers. 4 To investigate if nicotine could contribute to the increased CYP2E1 observed in alcoholic smokers, we treated human neuroblastoma IMR-32 cells in culture and found significantly higher CYP2E1 immunostaining in nicotine-treated cells (0.1-10 nM). 5. CYP2E1 induction in the brain, by ethanol or nicotine, may influence the central effects of ethanol and the development of nervous tissue pathologies observed in alcoholics and smokers.

Induction of nicotine-metabolizing CYP2B1 by ethanol and ethanol-metabolizing CYP2E1 by nicotine: summary and implications

Alcohol and tobacco are frequently co-abused. Increased alcohol use and alcoholism are associated with smoking, and vice versa. Functional and/or metabolic cross-tolerance may contribute to this occurrence. This review summarizes recent studies published from our laboratory focusing on metabolic aspects of tolerance, which demonstrate that in rat, subchronic, behaviourally relevant doses of ethanol induce hepatic nicotine-metabolizing cytochrome P450 (CYP) 2B1, and that subchronically administered nicotine, at behaviourally relevant doses, induces hepatic ethanol-metabolizing CYP2E1. Increased CYP2B1 protein, mRNA and CYP2B1-mediated nicotine metabolism was observed following ethanol treatments. CYP2E1 protein and activity were induced by nicotine, but no changes were seen in levels of CYP2E1 mRNA. These data indicate that metabolic cross-tolerance may occur between nicotine and ethanol, suggesting that nicotine use may increase the elimination of ethanol, and ethanol use may increase the elimination of nicotine. Other implications, such as altered pharmacology and toxicology of drugs metabolized by these enzymes, as well as changes in pro-carcinogen and pro-toxin activation are also discussed.

Smoking cessation in the elderly

Today, two generations after the first Surgeon General's report, and with abundant evidence of the catastrophic consequences of smoking, no serious person can be unaware that smokers risk their lives and health. We also know that quitting smoking--at any age--promises significant health benefits. When offered the tools they need, older smokers quit smoking at rates comparable to those of younger smokers despite their skepticism, fatalism, and self-doubt. Older smokers should be encouraged to enter programs that stress the health benefits derived and identify the risks they are avoiding by quitting smoking. These programs establish quit dates, use sound behavioral modification techniques, provide strategies for stress management and relaxation, treat withdrawal symptoms, and provide regular and continuing follow-up. The patient is asked to make an existential change, and the physician should provide encouragement and promote self-confidence by emphasizing that, despite setbacks, with repeated efforts, success can be achieved. Clinicians can influence patients to quit smoking, and they should.

Relationship between Genetic Polymorphisms of Alcohol-metabolizing Enzymes and Changes in Risk Factors for Coronary Heart Disease Associated with Alcohol Consumption

Background: There are large individual variations in the responses of risk factors for coronary heart disease to alcohol consumption. To clarify the factors responsible for these individual variations, we studied the relationship between blood pressure, serum lipids, and uric acid and the genetic polymorphisms of alcohol dehydrogenase (ADH) 2 and aldehyde dehydrogenase (ALDH) 2 in alcohol drinkers.

Methods: We examined 133 male workers who drank &gt;300 g of alcohol per week. Information regarding lifestyle habits was obtained by questionnaire. The ADH2 genotype was determined by PCR and subsequent digestion with MaeIII. The ALDH2 genotype was determined based on amplified product length polymorphisms.

Results: When the workers were divided into three groups: the ADH21/21, ADH21/22, and ADH22/22 groups, the mean triglycerides and γ-glutamyl transpeptidase concentrations were significantly higher in the ADH22/22 group than in the ADH21/21 group. In addition, multiple logistic regression analysis showed that the frequencies of individuals whose systolic blood pressure, triglycerides, and uric acid values were in the highest one third were significantly higher in the ADH22/22 group than in the ADH21/21 group. In contrast, no difference was observed between the ALDH21/21 and (ALDH21/22 + ALDH22/22) groups with regard to the mean value of any variable and to the frequency of individuals with any variable value in the highest one third.

Conclusion: Individuals with the ADH21/21 genotype might suffer fewer negative effects of drinking.

The role of pharmacogenetically-variable cytochrome P450 enzymes in drug abuse and dependence

The risk of drug dependence is determined by the interaction of drug, individual and environment. 'Pharmacogenetics' is the study of the influence of heredity on the response to drugs and their fate in the body; these studies aim to improve the understanding of inter-individual variability in drug response. The authors have applied this research approach to the study of drug metabolism and dependence. Specifically the interaction of genetically variable hepatic cytochrome P450 (CYP) enzymes and their effect on self-administration of drugs has been examined. Many drugs of abuse are substrates (e.g., amphetamines, codeine, nicotine) or inhibitors (e.g., (-)-cocaine) of polymorphic CYPs. Drug metabolism by genetically polymorphic enzymes can have significant clinical implications relating to drug toxicity, therapeutic failure, drug-drug interactions, disease susceptibility and abuse liability. There is good evidence that drug metabolism by genetically variable CYPs can influence the risk of drug dependence, the amount of drug consumed by dependent individuals and some of the toxicities associated with drug-taking behavior. It is anticipated that pharmacogenetics will be used to identify individuals at a greater risk for specific drug dependencies, provide information that can lead to novel treatment and prevention approaches as well as provide guidance for individualization of treatment choice.

Gender differences in alcohol metabolism. Physiological responses to ethanol

A gender difference in alcohol pharmacokinetics has been suggested to explain why women are more vulnerable to ethanol's toxic effects. The results of animal experiments suggest that females exhibit higher alcohol metabolic rates than males as a result of hormonal differences. Experimental results examining gender differences in human alcohol metabolism have been inconsistent; the diversity of experimental protocols and variety of pharmacokinetic parameters reported have made comparisons of these studies very difficult. Variability in alcohol metabolic rate between individuals of the same sex is often significant, preventing an assessment of gender differences in some studies. This chapter attempts to summarize the findings of studies from the last decade that examined the role of gender and sex hormone differences on ethanol metabolism in men and women. The role of body composition, genetic factors, gastric and hepatic alcohol dehydrogenase, and gastric absorption in creating gender differences in alcohol metabolism is discussed. Suggestions are offered that may result in better cross-study comparisons and more consistent experimental results.

Research advances in ethanol metabolism

The pharmacokinetics of alcohol determines the time course of alcohol concentration in blood after the ingestion of an alcoholic beverage and the degree of exposure of organs to its effects. The interplay between the kinetics of absorption, distribution and elimination is thus important in determining the pharmacodynamic responses to alcohol. There is a large degree of variability in alcohol absorption, distribution and metabolism, as a result of both genetic and environmental factors. The between-individual variation in alcohol metabolic rates is, in part due to allelic variants of the genes encoding the alcohol metabolizing enzymes, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). This review summarizes recent developments in the investigation of the following influences on alcohol elimination rate: gender, body composition and lean body mass, liver volume, food and food composition, ethnicity, and genetic polymorphisms in alcohol metabolizing enzymes as well as in the promoter regions of the genes for these enzymes. Evaluation of the factors regulating the rates of alcohol and acetaldehyde metabolism, both genetic and environmental, will help not only to explain the risk for development of alcoholism, but also the risk for development of alcohol-related organ damage and developmental problems.

Association of D2 dopamine receptor and alcohol dehydrogenase 2 genes with Polynesian alcoholics

Alleles of the D2 dopamine receptor (DRD2) and the alcohol dehydrogenase 2 (ADH2) genes were determined in 69 French Polynesian alcoholic patients and 57 controls matched for racial origin. Three racial groups were studied: pure Polynesians (PP), Polynesians mixed with Caucasian (PCA) ancestry and Polynesians mixed with Chinese (PCH) ancestry. DRD2 A1 allele frequencies in the alcoholics compared to their controls in these groups were: PP,.26 vs.32 (P =. 69); PCA,.44 vs.35 (P =.46); PCH,.40 vs 0.39 (P =.88). ADH2 1 allele frequencies in alcoholics compared to their controls groups were: PP, .56 vs.62 (P =.66); PCA,.75 vs.56 (P =.09); PCH,.78 vs.32 (P =.009). In the PCA group, the combination of the DRD2 A1 genotypes and the ADH2 1 homozygotes was strongly associated with alcoholism (P =. 0027). This preliminary study shows the importance of ascertaining racial ancestry in molecular genetic association studies. Moreover, it suggests that a combination of genes are involved in susceptibility to the development of alcoholism.

Effects of moderate alcohol consumption on the central nervous system

The concept of moderate consumption of ethanol (beverage alcohol) has evolved over time from considering this level of intake to be nonintoxicating and noninjurious, to encompassing levels defined as "statistically" normal in particular populations, and the public health-driven concepts that define moderate drinking as the level corresponding to the lowest overall rate of morbidity or mortality in a population. The various approaches to defining moderate consumption of ethanol provide for a range of intakes that can result in blood ethanol concentrations ranging from 5 to 6 mg/dl, to levels of over 90 mg/dl (i.e., approximately 20 mM). This review summarizes available information regarding the effects of moderate consumption of ethanol on the adult and the developing nervous systems. The metabolism of ethanol in the human is reviewed to allow for proper appreciation of the important variables that interact to influence the level of exposure of the brain to ethanol once ethanol is orally consumed. At the neurochemical level, the moderate consumption of ethanol selectively affects the function of GABA, glutamatergic, serotonergic, dopaminergic, cholinergic, and opioid neuronal systems. Ethanol can affect these systems directly, and/or the interactions between and among these systems become important in the expression of ethanol's actions. The behavioral consequences of ethanol's actions on brain neurochemistry, and the neurochemical effects themselves, are very much dose- and time-related, and the collage of ethanol's actions can change significantly even on the rising and falling phases of the blood ethanol curve. The behavioral effects of moderate ethanol intake can encompass events that the human or other animal can perceive as reinforcing through either positive (e.g., pleasurable, activating) or negative (e.g., anxiolysis, stress reduction) reinforcement mechanisms. Genetic factors and gender play an important role in the metabolism and behavioral actions of ethanol, and doses of ethanol producing pleasurable feelings, activation, and reduction of anxiety in some humans/animals can have aversive, sedative, or no effect in others. Research on the cognitive effects of acute and chronic moderate intake of ethanol is reviewed, and although a number of studies have noted a measurable diminution in neuropsychologic parameters in habitual consumers of moderate amounts of ethanol, others have not found such changes. Recent studies have also noted some positive effects of moderate ethanol consumption on cognitive performance in the aging human. The moderate consumption of ethanol by pregnant women can have significant consequences on the developing nervous system of the fetus. Consumption of ethanol during pregnancy at levels considered to be in the moderate range can generate fetal alcohol effects (behavioral, cognitive anomalies) in the offspring. A number of factors--including gestational period, the periodicity of the mother's drinking, genetic factors, etc.--play important roles in determining the effect of ethanol on the developing central nervous system. A series of recommendations for future research endeavors, at all levels, is included with this review as part of the assessment of the effects of moderate ethanol consumption on the central nervous system.

Alcohol effects on the heritability of EEG spectral power

To estimate the effects of a moderate dose of alcohol on heritability of the EEG power spectrum, 53 monozygotic and 38 like-sexed dizygotic Caucasian twin pairs (aged 30.0 +/- 7.0 years) were studied. Subjects were asked not to drink alcohol for 2 days and to fast after midnight before a protocol of: (1) a low fat meal at 8:00 AM; (2) a baseline EEG recording; (3) ingestion of alcohol over 10 min, which raised the breath alcohol concentration to 0.057 +/- 0.017% (SD); followed by (4) a postalcohol EEG recording 35.1 +/- 5.7 (SD) min after the start of drinking. One previous study (Propping, P., Hum. Genet. 35: 309-334, 1977) found that heritability (H2), the fraction of total variance in the EEG power that is attributable to genetic influences, increased after alcohol administration. In the current study, H2 of log-transformed, body-weight-adjusted spectral band power increased after alcohol for the theta-, alpha-slow, alpha-fast, beta-slow, and beta-fast bands (from an average of 0.47 to an average of 0.80). The increase in heritability was accompanied by a significant decrease in the within-pair differences of monozygotic cotwins for all of the same frequency bands except beta-fast. Because within-pair differences are expected to contain only environmental factors for the genetically identical individuals, it was concluded that alcohol decreases environmental variation of EEG power spectral density, causing the increase in H2.

Alcohol elimination in Native American Mission Indians: an investigation of interindividual variation

The high prevalence of alcohol abuse and alcohol dependence among Native Americans may be mediated by unique environmental and genetic factors in this population. One factor that may influence the development of alcoholism is variability in alcohol metabolism. To determine factors that contribute to differences in alcohol elimination rates within a Native American population, this study evaluated healthy southern California Mission Indian men between the ages of 18 and 25 years. Each man drank a dose of alcohol, 0.56 g/kg of body weight as a 20% by volume solution, at approximately 9:00 AM after eating a low-fat breakfast and having fasted overnight. The drink was consumed within 7 min, and the concentrations of alcohol in blood were determined before and at 15, 30, 60, 90, 120, and 150 min after beverage ingestion. Rates of alcohol elimination were calculated from the pseudolinear slope of the blood alcohol versus time curve. The influences of estimated body water, recent drinking history, recent smoking history, polymorphism at the ADH2 and ADH3 loci, family history of alcoholism, and percentage Native American heritage on alcohol elimination rate were determined using multiple regression analyses. Estimated body water accounted for a significant proportion of the variance in alcohol elimination rate. There was also a nonsignificant trend for subjects with an ADH2*3 allele (n = 6) to have faster rates of alcohol elimination than those with ADH2*1 alleles only (n = 33). Given the high prevalence of alcoholism and alcohol-related health problems among Native Americans, the results from this study suggest that evaluation of alcohol metabolism and genotypes of the alcohol-metabolizing enzymes in Native American populations merits further study.

Disposition and first-pass metabolism of ethanol in humans: is it gastric or hepatic and does it depend on gender?

OBJECTIVE

To assess the extent and site of the first-pass metabolism of ethanol and to examine whether first-pass metabolism and disposition of ethanol are dependent on gender.

METHODS

After a standardized lunch, healthy subjects (six women and six men) received on two separate occasions a 60-minute intravenous infusion of ethanol (0.3 gm/kg) and concomitantly an equimolar dose of d3-ethanol/kg either orally (over 20 minutes) or intraduodenally (infused over 30 minutes). Blood levels, urinary excretion of d0- and d3-ethanol, and sedative effects were monitored for 6 hours. Disposition and first-pass metabolism of ethanol were evaluated by applying an open two-compartment model with Michaelis-Menten elimination.

RESULTS

Comparison of the corresponding intravenous/oral versus intravenous/intraduodenal data of each individual revealed that total first-pass metabolism (gastric plus hepatic) was not pronounced in either males (9.1% +/- 4.0%; mean +/- SD) or females (8.4% +/- 3.1%) and that this first-pass metabolism was partly of gastric origin. Dose-corrected values for area under blood concentration-time curve were on average 28% higher (p < 0.0001) in the women than in the men. Mean total blood ethanol disappearance rate was higher (p < 0.001) in women (3.92 +/- 0.40 mmol/L . hr) than in men (3.19 +/- 0.48 mmol/L . hr). Renal clearance was gender-independent and negligible. A linear relationship (p < 0.001) could be found between the blood levels of ethanol and sedation index. Because the slope was steeper in women (1.04) than in men (0.42) a higher central nervous system sensitivity to the sedative effects of ethanol in women can be assumed.

CONCLUSIONS

Under realistic life conditions (social drinking of moderate doses of ethanol after a light lunch) only a minor, gender-independent first-pass metabolism is observed that is partly of gastric origin.

Molecular biological aspects of alcohol-induced liver disease

Molecular biological investigations have become a predominant methodology applied to the study of alcohol-induced liver disease. The enzymatic pathways responsible for ethanol metabolism, and their genetic as well as environmental control, have become the focus of detailed investigation. More recently, the significance of cytokines in the pathogenesis of alcohol-induced liver disease has also become a major area of speculation. This review focuses on the advances made in studies of two important enzymes responsible for alcohol metabolism, alcohol dehydrogenase and aldehyde dehydrogenase, as well as the investigation of the proinflammatory and profibrogenic cytokines involved in the process of hepatic fibrogenesis. The quality and quantity of new discoveries made in the field of alcohol-induced liver disease is impressive, especially when one realizes that molecular biological approaches have been employed in this area for only 15 years. However, in most cases the studies have been predominantly descriptive, with little direct relevance to the therapeutics of alcoholism and alcohol-induced organ injury. Because the groundwork has been laid, one hopes that the next 15 years will rectify this failure.

Genetic differences in drug disposition

Genetic polymorphisms of drug metabolizing enzymes are well recognized. This review presents molecular mechanisms, ontogeny and clinical implications of genetically determined intersubject variation in some of these enzymes. Included are the polymorphic enzymes N-acetyl transferase, cytochromes P4502D6 and 2C, which have been well described in humans. Information regarding other Phase I and Phase II polymorphic pathways, such as glutathione and methyl conjugation and alcohol and acetaldehyde oxidation continues to increase and are also discussed. Genetic factors effecting enzyme activity are frequently important determinants of the disposition of drugs and their efficacy and toxicity. In addition, associations between genetic differences in these enzymes and susceptibility to carcinogens and teratogens have been reported. Ultimately, the application of knowledge regarding these genetic factors of enzyme activity may guide medical therapy and minimize xenobiotic-induced disease.

Between-subject and within-subject variations in the pharmacokinetics of ethanol

1. Twelve healthy men drank 0.80 g ethanol kg-1 body weight on four occasions spread over several weeks. Ethanol was given as 96% v/v solvent which was diluted with orange juice to make a cocktail (20-25% v/v). This drink was ingested in exactly 30 min at 08.00 h after an overnight (10 h) fast. 2. Samples of venous blood were obtained at exactly timed intervals of 0, 10, 20, 30, 45, 60, 90, 120, 150, 180, 240, 300, and 360 min after the start of drinking. The concentrations of ethanol in whole blood were determined by headspace gas chromatography. 3. Summary measures were used to evaluate the concentration-time profiles of ethanol for each subject. The between-subject and within-subject components of variation for the pharmacokinetics of ethanol were derived by one-way analysis of variance (ANOVA). 4. The variation between different subjects dominated the total variance for all of the pharmacokinetic parameters studied except the rate of disappearance of ethanol from blood (ko). For this latter parameter, 42% and 58% of the total variation arose from variations between- and within-subjects respectively. These results might be important to consider when experiments on the clinical pharmacokinetics of ethanol are being planned.

Alcohol and aldehyde dehydrogenase polymorphisms and alcoholism

The alcohol-flush reaction occurs in Asians who inherit the mutant ALDH2*2 allele that produces an inactive aldehyde dehydrogenase enzyme. In these individuals, high blood acetaldehyde levels are believed to be the cause of the unpleasant symptoms that follow drinking. We measured the alcohol elimination rates and intensity of flushing in Chinese subjects in whom the alcohol dehydrogenase ADH2 and ALDH2 genotypes were determined. We also correlated ADH2, ADH3, and ALDH2 genotypes with drinking behavior in 100 Chinese men. We discovered that ADH2*2 and ADH3*1, alleles that encode the high activity forms of alcohol dehydrogenase, as well as the mutant ALDH2*2 allele were less frequent in alcoholics than in controls. The presence of ALDH2*2 was associated with slower alcohol metabolism and the most intense flushing. In those homozygous for ALDH2*1, the presence of two ADH2*2 alleles correlated with slightly faster alcohol metabolism and more intense flushing, although a great deal of variability in the latter was noted.

Does psychomotor sensitivity to alcohol predict subsequent alcohol use?

Data from 42 male and 58 female subjects who participated in the Colorado Alcohol Research on Twins and Adoptees (CARTA) project were subjected to model-fitting analyses. The aim of the present study was to use linear structural equation models to determine whether differences in previously measured psychomotor sensitivity to alcohol predict differences in self-reported alcohol consumption over a 4-year period. LISREL model-fitting results indicate that, for male subjects, only rail walking insensitivity is predictive of alcohol use reported 2 years after their initial CARTA testing. For females, only hand steadiness sensitivity is predictive of alcohol use reported 2 years after their initial CARTA testing. The results for males support a hypothesis that would consider alcohol insensitive individuals at greater risk for alcohol abuse. The female results, however, would argue against such a hypothesis. With only one measure of sensitivity predicting alcohol use at only one out of four time points, in both men and women, the overall results suggest that our three measures of psychomotor sensitivity to alcohol are, in general, poor predictors of alcohol consumption in this sample.

Ethanol kinetics: extent of error in back extrapolation procedures

1. Plasma ethanol concentrations were measured in 24 male volunteers for 9 h after a single oral dose of 710 mg kg-1. 2. The rate of decline of the plasma ethanol concentration (k0; mean +/- s.d.), was 186 +/- 26 mg l-1 h-1. 3. In each individual, three elimination rates were used to back-extrapolate plasma ethanol concentrations over 3 and 5 h periods from observed values at 4 h and 6 h post-dosing assuming zero-order kinetics. The extrapolated values were then compared with the observed concentrations. 4. Using the mean k0 values for the subjects the mean error in back extrapolation was small but highly variable. The variability in the error increased with the length of the extrapolation period. 5. When a k0 value of 150 mg l-1 h-1 (a value often cited as a population mean) was used for back extrapolation this resulted in significant under-estimation of actual values whereas the use of a k0 value of 238 mg l-1 h-1 (the highest value observed in the present study) resulted in significant over-estimation of actual values. 6. These results indicate that because the kinetics of ethanol are associated with substantial inter-subject variability the use of a single slope value to back calculate blood concentrations can give rise to considerable error.

One-month repeatability of emotional responses to alcohol

Thirty-four subjects in the Colorado Alcohol Research on Twins and Adoptees (CARTA) were brought back between 30 to 60 days after their initial testing to be retested on all the CARTA procedures. As before, subjects were given a dose of ethanol (0.8 g/kg) calculated to bring their blood alcohol concentration (BAC) to near 0.10 g/dl. Additional doses were given at the end of each of the next 2 hr to maintain their BAC near peak for approximately 3 hr. During both testings, subjects' self-reports of their emotional responses and perceived intoxication following alcohol dosing were only minimally correlated with their alcohol metabolism parameters and reported average level of alcohol use. Repeatabilities (test-retest correlations) for subjects' self-reports of positive affect and of intoxication following alcohol dosing were consistently high, in contrast to earlier reports of minimal repeatabilities for alcohol metabolism and responses to alcohol on physiological, motor coordination, reaction time, and perceptual speed measures. Tester ratings of the subjects' levels of intoxication were also moderately stable between the two testings.

Experimental model for the investigation of kinetic and/or dynamic interactions between drugs and ethanol in humans

This study was performed to establish an experimental method for the investigation of interactions between ethanol and drugs under predictable and controlled conditions. The model was tested with flumazenil (Ro 15-1788), a short-acting benzodiazepine antagonist with an elimination half-life of 1 h. Six healthy volunteers (5 males, 1 female) were administered ethanol by intravenous infusion with stepwise changing rates. The infusion rates were adapted to each subject on the basis of individual disposition parameters of ethanol, which were derived from preceding short-term infusions of 120 min duration (1.0 mg/kg in males, 0.8 mg/kg in the female). This two-step procedure led to individual ethanol plasma levels between 1.47 +/- 0.04 and 1.71 +/- 0.03 g/L, which were reached after 2.5 h and thereafter maintained over another 6 h. Within the period of constant ethanol levels, single doses of flumazenil and placebo, respectively, were injected intravenously as a bolus (2 min) in a double-blind fashion according to a randomized two-way crossover design. Three subjects received a dose of 0.10 mg/kg of flumazenil, and the remaining three subjects received a dose of 0.20 mg/kg. Evaluation of the plasma concentration time curves of flumazenil did not reveal evidence of an effect of ethanol on the pharmacokinetics of this drug.

Alcoholism: early diagnosis and intervention

Alcoholism, more than any other illness, requires the integration of social and family history, physical symptoms and signs, and laboratory data in order to make a firm diagnosis. Common in alcoholism is the patient's minimization or denial of the disease and its symptoms, thwarting efforts at early diagnosis and intervention. If early diagnosis is to be made, several points should be remembered: 1. Life problems associated with alcohol use are the earliest signs of the disease. 2. There are few reliable early physical symptoms and signs. 3. Laboratory markers of alcoholism are neither sensitive nor specific when used alone as screening tools. 4. Alcoholism questionnaires, e.g., the MAST or the CAGE, should be a part of routine office practice in screening for alcoholism. Effective therapy is available, but early diagnosis is necessary for the best outcome. Gallant has reminded us of the "tragedy of delayed treatment." Early recognition of alcoholism puts the internist, as well as other primary care providers, in the best position to begin the process of healing the patients and their families.

International Commission for Protection against Environmental Mutagens and Carcinogens. ICPEMC Working Paper No. 15/5. Acute aldehyde syndrome and chronic aldehydism

Different types of alcohol dehydrogenase and of aldehyde dehydrogenase lead to different blood acetaldehyde levels. With respect to acetaldehyde levels in human blood 3 types can be distinguished: (1) the normal range, (2) the acute aldehyde syndrome, and (3) the chronic aldehydism. Acetaldehyde is electrophilic and reacts with nucleophilic groups of various macromolecules including DNA. Acetyldehyde inhibits synthetic and metabolic pathways, it interferes with the polymerization of tubulin and stimulates collagen synthesis. By depletion of cellular glutathione levels, acetaldehyde leads to lipid peroxidation and to the formation of malonaldehyde. There are indications that acetaldehyde may play a role in positively reinforcing mood changes induced by alcohol in humans.

Factors affecting the drinking driver

Although the relationship between alcohol and traffic safety has been the subject of numerous studies, much remains unknown about the mechanisms by which alcohol contributes to traffic accidents. A number of other factors, which are reviewed in this paper, also can contribute to car accidents. They may also interact with alcohol, perhaps in a complex manner. Therefore, multiple factors rather than one single factor may contribute to automobile accidents for those who drink and drive.

Ethanol metabolism

Alcohol is metabolized by two pathways in humans: the ADH pathway which accounts for the bulk of the metabolism, and the MEOS pathway which contributes to the increased rate of ethanol elimination at high blood alcohol levels. The increased rate of elimination which results from chronic alcohol consumption is due to an increase in MEOS activity. The activities of these pathways are influenced by environmental factors such as smoking, diet, and endocrine factors. In addition, individuals inherit different types of ADH isoenzymes which have different kinetic properties. Individuals with different phenotypic variants, e.g. the beta 1 vs beta 2 isoenzymes, appear to have different rates of ethanol elimination. The cloning of the ADH genes and the availability of molecular hybridization methods now make it possible to genotype individuals and to correlate the genotype with both alcohol elimination rates and with the risk of developing medical complications of alcoholism or even of developing alcoholism itself.