Pharmacokinetics of ethanol: a review

Integration of a physiologically-based pharmacokinetic model with a whole-body, organ-resolved genome-scale model for characterization of ethanol and acetaldehyde metabolism

Ethanol is one of the most widely used recreational substances in the world and due to its ubiquitous use, ethanol abuse has been the cause of over 3.3 million deaths each year. In addition to its effects, ethanol's primary metabolite, acetaldehyde, is a carcinogen that can cause symptoms of facial flushing, headaches, and nausea. How strongly ethanol or acetaldehyde affects an individual depends highly on the genetic polymorphisms of certain genes. In particular, the genetic polymorphisms of mitochondrial aldehyde dehydrogenase, ALDH2, play a large role in the metabolism of acetaldehyde. Thus, it is important to characterize how genetic variations can lead to different exposures and responses to ethanol and acetaldehyde. While the pharmacokinetics of ethanol metabolism through alcohol dehydrogenase have been thoroughly explored in previous studies, in this paper, we combined a base physiologically-based pharmacokinetic (PBPK) model with a whole-body genome-scale model (WBM) to gain further insight into the effect of other less explored processes and genetic variations on ethanol metabolism. This combined model was fit to clinical data and used to show the effect of alcohol concentrations, organ damage, ALDH2 enzyme polymorphisms, and ALDH2-inhibiting drug disulfiram on ethanol and acetaldehyde exposure. Through estimating the reaction rates of auxiliary processes with dynamic Flux Balance Analysis, The PBPK-WBM was able to navigate around a lack of kinetic constants traditionally associated with PK modelling and demonstrate the compensatory effects of the body in response to decreased liver enzyme expression. Additionally, the model demonstrated that acetaldehyde exposure increased with higher dosages of disulfiram and decreased ALDH2 efficiency, and that moderate consumption rates of ethanol could lead to unexpected accumulations in acetaldehyde. This modelling framework combines the comprehensive steady-state analyses from genome-scale models with the dynamics of traditional PK models to create a highly personalized form of PBPK modelling that can push the boundaries of precision medicine.

The failings of per se limits to detect cannabis-induced driving impairment: Results from a simulated driving study

OBJECTIVE

Many jurisdictions use per se limits to define cannabis-impaired driving. Previous studies, however, suggest that THC concentrations in biological matrices do not reliably reflect cannabis dose and are poorly correlated with magnitude of driving impairment. Here, we first review a range of concerns associated with per se limits for THC. We then use data from a recent clinical trial to test the validity of a range of extant blood and oral fluid THC per se limits in predicting driving impairment during a simulated driving task.

METHODS

Simulated driving performance was assessed in 14 infrequent cannabis users at two timepoints (30 min and 3.5 h) under three different conditions, namely controlled vaporization of 125 mg (i) THC-dominant (11% THC; <1% CBD), (ii) THC/CBD equivalent (11% THC; 11% CBD), and (iii) placebo (<1% THC & CBD) cannabis. Plasma and oral fluid samples were collected before each driving assessment. We examined whether per se limits of 1.4 and 7 ng/mL THC in plasma (meant to approximate 1 and 5 ng/mL whole blood) and 2 and 5 ng/mL THC in oral fluid reliably predicted impairment (defined as an increase in standard deviation of lateral position (SDLP) of >2 cm relative to placebo).

RESULTS

For all participants, plasma and oral fluid THC concentrations were over the per se limits used 30 min after vaporizing THC-dominant or THC/CBD equivalent cannabis. However, 46% of participants failed to meet SDLP criteria for driving impairment. At 3.5 h post-vaporization, 57% of participants showed impairment, despite having low concentrations of THC in both blood (median = 1.0 ng/mL) and oral fluid (median = 1.0 ng/mL). We highlight two individual cases illustrating how (i) impairment can be minimal in the presence of a positive THC result, and (ii) impairment can be profound in the presence of a negative THC result.

CONCLUSIONS

There appears to be a poor and inconsistent relationship between magnitude of impairment and THC concentrations in biological samples, meaning that per se limits cannot reliably discriminate between impaired from unimpaired drivers. There is a pressing need to develop improved methods of detecting cannabis intoxication and impairment.

In vitro metabolic profile and drug-drug interaction assessment of secnidazole, a high-dose 5-nitroimidazole antibiotic for the treatment of bacterial vaginosis

A single-dose oral granule formulation of secnidazole 2 g (SOLOSEC™ ) has been approved in the US as a treatment for bacterial vaginosis. Available data on the likelihood of in vitro drug-drug and alcohol-drug interactions are limited. Secnidazole was incubated with cultured human hepatocytes over a range of concentrations (0-10 000 μmol/L) to assess metabolic profiling. Cytochrome P450 (CYP) and aldehyde dehydrogenase inhibition over a similar concentration range were evaluated in human liver microsomes (HLMs) or recombinant enzymes using competition or time-dependent inactivation assays. Secnidazole exhibited very low metabolism in HLMs at concentrations up to 6400 µmol/L. Secnidazole was found to be metabolized to a limited extent predominantly by CYP3A4 and CYP3A5 among a panel of cDNA-expressed enzymes. Secnidazole inhibited CYP2C19 and CYP3A4, with IC50 values of 3873 and 3722 µmol/L, respectively. Secnidazole did not exhibit time-dependent inhibition. There was no inhibition (IC50 value >5000 µmol/L) observed for any other CYP enzyme or with human recombinant aldehyde dehydrogenase 2 (ALDH2). These results are the first reported observation of the metabolism and drug-drug interaction profile for secnidazole and demonstrate that the agent has minimal to no potential drug interactions of concern.

Myrtle berries seeds aqueous extract abrogates chronic alcohol consumption-induced erythrocytes osmotic stability disturbance, haematological and biochemical toxicity

BACKGROUND

This study examined the effects of chronic alcohol consumption in the rat erythrocytes membrane as well as the involvement of reactive oxygen species and proinflammatory cytokines in its pathogenicity in rats and evaluated the ameliorating effects of myrtle berries seeds aqueous extract (MBSAE).

METHODS

Fifty adult male Wistar rats were equally divided into five groups and treated daily for two months as follows: control, ethanol (3 g kg^- 1 b.w., p.o.), and ethanol + MBSAE (25, 50 and 100 mg kg^- 1, b.w., p.o.).

RESULTS

Exposure of rats to alcohol caused significant changes of some haematological parameters, enhanced erythrocytes hemolysis as well as an overproduction of reactive oxygen species such as H₂O₂, OH^• radical and superoxide anion, hence the increase of lipoperoxidation and the depletion of antioxidant enzymes activity as well as non-enzymatic antioxidant (-SH groups and GSH) levels. On the other hand, ethanol intoxication caused the increase of serum TNFα, IL-8, IL-6 and 1Lβ, markers of tissue inflammation. However, treatment with MBSAE alleviated all the deleterious effects of alcohol consumption.

CONCLUSIONS

MBSAE possess active compounds, which exert marked protective effects in chronic alcohol intoxication, possibly by regulating the erythrocytes osmotic stability as well as antioxidant and inflammatory mediators.

Dynamics of Metabolism and Decision Making During Alcohol Consumption: Modeling and Analysis

Heavy alcohol consumption is considered an important public health issue in the United States as over 88 000 people die every year from alcohol-related causes. Research is being conducted to understand the etiology of alcohol consumption and to develop strategies to decrease high-risk consumption and its consequences, but there are still important gaps in determining the main factors that influence the consumption behaviors throughout the drinking event. There is a need for methodologies that allow us not only to identify such factors but also to have a comprehensive understanding of how they are connected and how they affect the dynamical evolution of a drinking event. In this paper, we use previous empirical findings from laboratory and field studies to build a mathematical model of the blood alcohol concentration dynamics in individuals that are in drinking events. We characterize these dynamics as the result of the interaction between a decision-making system and the metabolic process for alcohol. We provide a model of the metabolic process for arbitrary alcohol intake patterns and a characterization of the mechanisms that drive the decision-making process of a drinker during the drinking event. We use computational simulations and Lyapunov stability theory to analyze the effects of the parameters of the model on the blood alcohol concentration dynamics that are characterized. Also, we propose a methodology to inform the model using data collected in situ and to make estimations that provide additional information to the analysis. We show how this model allows us to analyze and predict previously observed behaviors, to design new approaches for the collection of data that improves the construction of the model, and help with the design of interventions.

Acute ethanol administration results in a protective cytokine and neuroinflammatory profile in traumatic brain injury

Ethanol intoxication is a common comorbidity in traumatic brain injury. To date, the effect of ethanol on TBI pathogenic cascades and resulting outcomes remains debated. A closed blunt weight-drop murine TBI model has been implemented to investigate behavioral (by sensorimotor and neurological tests), and neuro-immunological (by tissue cytokine arrays and immuno-histology) effects of ethanol intoxication on TBI. The effect of the occurrence of traumatic intracerebral hemorrhage was also studied. The results indicate that ethanol pretreatment results in a faster and better recovery after TBI with reduced infiltration of leukocytes and reduced microglia activation. These outcomes correspond to reduced parenchymal levels of GM-CSF, IL-6 and IL-3 and to the transient upregulation of IL-13 and VEGF, indicating an early shift in the cytokine profile towards reduced inflammation. A significant difference in the cytokine profile was still observed 24h post injury in the ethanol pretreated mice, as shown by the delayed peak in IL-6 and by the suppression of GM-CSF, IFN-γ, and IL-3. Seven days post-injury, ethanol-pretreated mice displayed a significant decrease both in CD45+ cells infiltration and in microglial activation. On the other hand, in the case of traumatic intracerebral hemorrhage, the cytokine profile was dominated by KC, CCL5, M-CSF and several interleukins and ethanol pretreatment did not produce any modification. We can thus conclude that ethanol intoxication suppresses the acute neuro-inflammatory response to TBI, an effect which is correlated with a faster and complete neurological recovery, whereas, the presence of traumatic intracerebral hemorrhage overrides the effects of ethanol.

Inhalation of Alcohol Vapor: Measurement and Implications

Decades of alcohol research have established the health risks and pharmacodynamic profile of oral alcohol consumption. Despite isolated periods of public health concern, comparatively less research has evaluated exposure to alcohol vapor. Inhaled alcohol initially bypasses first-pass metabolism and rapidly reaches the arterial circulation and the brain, suggesting that this route of administration may be associated with pharmacological effects that increase the risk of addiction. However, detailed reviews assessing the possible effects of inhaled alcohol in humans are lacking. A comprehensive, systematic literature review was conducted using Google Scholar and PubMed to examine manuscripts studying exposure to inhaled alcohol and measurement of biomarkers (biochemical or functional) associated with alcohol consumption in human participants. Twenty-one publications reported on alcohol inhalation. Fourteen studies examined inhalation of alcohol vapor associated with occupational exposure (e.g., hand sanitizer) in a variety of settings (e.g., naturalistic, laboratory). Six publications measured inhalation of alcohol in a controlled laboratory chamber, and 1 evaluated direct inhalation of an e-cigarette with ethanol-containing "e-liquid." Some studies have reported that inhalation of alcohol vapor results in measurable biomarkers of acute alcohol exposure, most notably ethyl glucuronide. Despite the lack of significantly elevated blood alcohol concentrations, the behavioral consequences and subjective effects associated with repeated use of devices capable of delivering alcohol vapor are yet to be determined. No studies have focused on vulnerable populations, such as adolescents or individuals with alcohol use disorder, who may be most at risk of problems associated with alcohol inhalation.

The different effects on cranial and trunk neural crest cell behaviour following exposure to a low concentration of alcohol in vitro

Embryonic neural crest cells give rise to large regions of the face and peripheral nervous system. Exposure of these cells to high alcohol concentrations leads to cell death in the craniofacial region resulting in facial defects. However, the effects of low concentrations of alcohol on neural crest cells are not clear. In this study, cranial neural crest cells from Xenopus laevis were cultured in an ethanol concentration approximately equivalent to one drink. Techniques were developed to study various aspects of neural crest cell behaviour and a number of cellular parameters were quantified. In the presence of alcohol, a significant number of cranial neural crest cells emigrated from the explant on fibronectin but the liberation of individual cells was delayed. The cells also remained close to the explant and their morphology changed. Cranial neural crest cells did not grow on Type 1 collagen. For the purposes of comparison, the behaviour of trunk neural crest cells was also studied. The presence of alcohol correlated with increased retention of single cells on fibronectin but left other parameters unchanged. The behaviour of trunk neural crest cells growing on Type 1 collagen in the presence of alcohol did not differ from controls. Low concentrations of alcohol therefore significantly affected both cranial and trunk neural crest cells, with a wider variety of effects on cells from the cranial as opposed to the trunk region. The results suggest that low concentrations of alcohol may be more detrimental to early events in organ formation than currently suspected.

Synergetic neuroprotection of normobaric oxygenation and ethanol in ischemic stroke through improved oxidative mechanism

BACKGROUND AND PURPOSE

Normobaric oxygenation (NBO) and ethanol both provide neuroprotection in stroke. We evaluated the enhanced neuroprotective effect of combining these 2 treatments in a rat stroke model.

METHODS

Sprague-Dawley rats were subjected to middle cerebral artery occlusion for 2 hours. Reperfusion was then established and followed by treatment with either (1) an intraperitoneal injection of ethanol (1.0 g/kg), (2) NBO treatment (2-hour duration), or (3) NBO plus ethanol. The extent of brain injury was determined by infarct volume and motor performance. Oxidative metabolism was determined by ADP/ATP ratios, reactive oxygen species levels, nicotinamide adenine dinucleotide phosphate oxidase activity, and pyruvate dehydrogenase activity. Protein expression of major nicotinamide adenine dinucleotide phosphate oxidase subunits (p47(phox), gp91(phox), and p67(phox)) and the enzyme pyruvate dehydrogenase was evaluated through Western immunoblotting.

RESULTS

NBO and ethanol monotherapies each demonstrated reductions as compared to stroke without treatment in infarct volume (36.7% and 37.9% vs 48.4%) and neurological deficits (score of 6.4 and 6.5 vs 8.4); however, the greatest neuroprotection (18.8% of infarct volume and 4.4 neurological deficit) was found in animals treated with combination therapy. This neuroprotection was associated with the largest reductions in ADP/ATP ratios, reactive oxygen species levels, and nicotinamide adenine dinucleotide phosphate oxidase activity, and the largest increase in pyruvate dehydrogenase activity.

CONCLUSIONS

Combination therapy with NBO and ethanol enhances the neuroprotective effect produced by each therapy alone. The mechanism behind this synergistic action is related to changes in cellular metabolism after ischemia reperfusion. NBO plus ethanol is attractive for clinical study because of its ease of use, tolerability, and tremendous neuroprotective potential in stroke.

Is ADH1C genotype relevant for the cardioprotective effect of alcohol?

The cardioprotective effect of ethanol has been suggested to be linked to one of the ethanol metabolizing enzymes (ADH1C), which constitutes a high V(max) and a low V(max) variant. This has been demonstrated in some studies, while others have not been able to replicate the findings. The aim of the present study was to investigate the relation between the different ADH1C genotypes, death from coronary heart disease (CHD) and alcohol in a material larger than the previously published studies. Eight hundred CHD deaths as well as 1303 controls were genotyped for the high V(max) (γ1) and the low V(max) (γ2) ADH1C variant. Information of alcohol use was available for all subjects. Multiple logistic regression analyses was used to study if the decreased risk of death from CHD in alcohol consuming subjects was more pronounced in subjects homozygous for the γ2 allele (γ2γ2 subjects) compared to γ1γ1 and γ1γ2 subjects. The odds ratio (OR) for death from CHD in alcohol consumers compared to abstainers was similar in the genotype groups, i.e., 0.62 (95% CI: 0.43-0.88) in γ1γ1 subjects and 0.62 (95% CI: 0.42-0.91) in γ2γ2 subjects. Also when stratifying the results by gender and when dividing alcohol consumers into different alcohol consumption groups, there was no difference in the OR between the different genotype groups. This study, which included the largest study group published so far, failed to find any link between the ADH1C genotype and the cardioprotective effects of alcohol.

Central nervous system effects of alcohol at a pseudo-steady-state concentration using alcohol clamping in healthy volunteers

AIM

In determining the acute effects of alcohol, it is helpful if alcohol concentrations are maintained at stable levels, to facilitate the interpretation of the results. Recently, an alcohol clamping method was developed that resulted in stable alcohol concentrations for hours. The aim of this study was to test a range of central nervous system (CNS) effects under pseudo-steady-state conditions.

METHODS

To achieve a pseudo-steady state of 0.6 g l(-1), breath alcohol concentrations (BrAC) were frequently measured and fed back into a spreadsheet-based program to guide intravenous dosing. CNS effects were frequently measured throughout the clamp.

RESULTS

The clamping paradigm resulted in a pseudo-steady-state BrAC of 0.61 g l(-1) (coefficient of variation 6.2%). A plateau was maintained from 25 to 300 min and caused significant effects on smooth pursuit eye movements [-9.7%, 95% confidence interval (CI) -12.4, -7.1], adaptive tracking (-3.4%, 95% CI -4.5, -2.2), visual analogue scale (VAS) alertness (-13 mm, 95% CI -20, -6), VAS alcohol effects (16 mm, 95% CI 7, 25) and body sway (21.3%, 95% CI 1.8, 45). Some effects (like smooth pursuit eye movements) closely followed the relatively stable alcohol concentrations, whereas others (such as body sway and VAS alcohol effects) fluctuated during the plateau phase.

CONCLUSIONS

Most CNS effects of alcohol showed a trend to change over time, despite stable concentrations. Other variables remained stable under pseudo-steady-state conditions. The intravenous clamping method provides precise control over BrAC levels and allows frequent repetition of different CNS measurements. These features make this technique eminently suitable to study the complex pharmacodynamic effects of acute alcohol administration.

Beer consumption increases human attractiveness to malaria mosquitoes

Background

Malaria and alcohol consumption both represent major public health problems. Alcohol consumption is rising in developing countries and, as efforts to manage malaria are expanded, understanding the links between malaria and alcohol consumption becomes crucial. Our aim was to ascertain the effect of beer consumption on human attractiveness to malaria mosquitoes in semi field conditions in Burkina Faso.

Methodology/Principal Findings

We used a Y tube-olfactometer designed to take advantage of the whole body odour (breath and skin emanations) as a stimulus to gauge human attractiveness to Anopheles gambiae (the primary African malaria vector) before and after volunteers consumed either beer (n = 25 volunteers and a total of 2500 mosquitoes tested) or water (n = 18 volunteers and a total of 1800 mosquitoes). Water consumption had no effect on human attractiveness to An. gambiae mosquitoes, but beer consumption increased volunteer attractiveness. Body odours of volunteers who consumed beer increased mosquito activation (proportion of mosquitoes engaging in take-off and up-wind flight) and orientation (proportion of mosquitoes flying towards volunteers' odours). The level of exhaled carbon dioxide and body temperature had no effect on human attractiveness to mosquitoes. Despite individual volunteer variation, beer consumption consistently increased attractiveness to mosquitoes.

Conclusions/Significance

These results suggest that beer consumption is a risk factor for malaria and needs to be integrated into public health policies for the design of control measures.

Have I had one drink too many? Assessing gender differences in misperceptions of intoxication among college students

OBJECTIVE

The present study extends the literature on factors involved in college students' drinking tendencies by examining differences between men and women in their ability to accurately estimate personal intoxication. The study also assessed whether men and women who typically consume large quantities of alcohol when they attend parties have more difficulty accurately assessing intoxication compared with lighter drinkers.

METHOD

The research used the external cueing approach (ECA) of Turrisi and colleagues as the informational paradigm to examine 3,707 college students' gender, typical drinking at parties, and how they relate to perceptions of intoxication.

RESULTS

The study revealed that approximately 20% (n = 710) of participants underestimated their blood alcohol concentration using the ECA. Among participants who made underestimation errors, gender differences were observed in that women made significantly more underestimation errors in the scenarios that contained four to five drinks and men made more underestimation errors in the scenarios that contained six to seven drinks. In addition, a three-way interaction revealed that female students who reported typically drinking larger amounts of alcohol in party settings were more likely to make errors when estimating their intoxication for moderately high numbers of drinks (e.g., four to five drinks).

CONCLUSIONS

The results are discussed in terms of examining the importance of college student drinking, gender, typical alcohol consumption at a party, and estimation of intoxication. Implications of gender effects in relation to high-risk drinking activities (i.e., pregaming and drinking games) as well as prevention efforts are discussed.

Confirmatory analysis of buprenorphine, norbuprenorphine, and glucuronide metabolites in plasma by LCMSMS. Application to umbilical cord plasma from buprenorphine-maintained pregnant women

An LCMSMS method was developed and fully validated for the simultaneous quantification of buprenorphine (BUP), norbuprenorphine (NBUP), buprenorphine-glucuronide (BUP-Gluc), and norbuprenorphine-glucuronide (NBUP-Gluc) in 0.5mL plasma, fulfilling confirmation criteria with two transitions for each compound with acceptable relative ion intensities. Transitions monitored were 468.3>396.2 and 468.3>414.3 for BUP, 414.3>340.1 and 414.3>326.0 for NBUP, 644.3>468.1 and 644.3>396.3 for BUP-Gluc, and 590.3>414.3 and 590.3>396.2 for NBUP-Gluc. Linearity was 0.1-50ng/mL for BUP and BUP-Gluc, and 0.5-50ng/mL for NBUP and NBUP-Gluc. Intra-day, inter-day, and total assay imprecision (%RSD) were <16.8%, and analytical recoveries were 88.6-108.7%. Extraction efficiencies ranged from 71.1 to 87.1%, and process efficiencies 48.7 to 127.7%. All compounds showed ion enhancement, except BUP-Gluc that demonstrated ion suppression: variation between 10 different blank plasma specimens was <9.1%. In six umbilical cord plasma specimens from opioid-dependent pregnant women receiving 14-24mg/day BUP, NBUP-Gluc was the predominant metabolite (29.8+/-7.6ng/mL), with BUP-Gluc (4.6+/-4.8ng/mL), NBUP (1.5+/-0.8ng/mL) and BUP (0.4+/-0.2ng/mL). Although BUP biomarkers can be quantified in umbilical cord plasma in low ng/mL concentrations, the significance of these data as predictors of neonatal outcomes is currently unknown.

Age and gender differences in blood-alcohol concentration in apprehended drivers in relation to the amounts of alcohol consumed

This article reports the age, gender, and blood-alcohol concentration (BAC) of people apprehended in Sweden for driving under the influence of alcohol (DUIA) over an 8-year period (2000-2007). Duplicate determinations of ethanol were made in venous blood by headspace gas chromatography and results were reported positive at a cut-off concentration of 0.1 g/L (10 mg/100 ml or 0.01 g%). The mean, median and highest BAC was 1.74 g/L, 1.70 g/L and 5.18 g/L, respectively. The vast majority of offenders were men (89.5%) with a mean age of 39.0+/-14.6 y (+/-SD). The women (10.5%) were a few years older 41.8+/-13.6 y (p<0.001). The mean BAC in the men (1.73+/-0.85 g/L) did not differ significantly (p>0.05) from women (1.77+/-0.87 g/L). The youngest offenders aged 15-20 y (N=3513) had a mean BAC of 1.30+/-0.60 g/L (median 1.32), which was significantly less (p<0.001) than people aged 40-50 y (N=6644); mean 1.90 g/L (median 2.0 g/L). In 95 individuals (89 men and 6 women) the BAC exceeded 4.0 g/L, which is a level considered to cause death by acute alcohol poisoning. The Widmark formula was used to calculate that a man (80 kg) with a BAC of 1.7 g/L has 95 g ethanol (approximately 12 units of alcohol) in the body compared with 61 g (approximately 8 units) for a woman (60 kg). This study verifies that the average drunken driver in Sweden is typically a binge drinker and education programs and treatment for alcohol-use disorder might be a more appropriate sanction than the more conventional penalties for alcohol-impaired driving.

A comparative study of two methods for attaining constant alcohol levels

AIMS

Alcohol effects or drug-alcohol interactions are preferably studied at constant blood levels. To achieve pseudo-steady state levels, various methods are used, which usually produce adequate averages but variable individual concentration profiles. The aim was to compare two modes of alcohol administration: a 'two-step prekinetic procedure' and a 'clamping method'.

METHODS

The two-step prekinetic procedure started with determination of individual pharmacokinetic (PK) parameters, during a prestudy occasion. Individual infusion regimens were calculated afterwards, based on a pseudo-steady state breath alcohol concentration (BrAC) of 0.65 g l(-1) and applied on a separate occasion. For the clamping procedure, a spreadsheet-based paradigm was developed using BrAC-guided adjustments of infusion rates, to maintain stable BrAC levels of 0.6 g l(-1).

RESULTS

The mean BrAC during clamping [0.61 g l(-1), 95% confidence interval (CI) 0.58, 0.63] did not differ from its intended level of 0.6 g l(-1) (1.0% on average). In contrast, the mean BrAC during the prekinetic procedure was significantly lower than the 0.65 g l(-1) set-point (0.59 g l(-1), 95% CI 0.54, 0.63) and deviated from this target by 9.7% on average. The clamping method also showed less variation between subjects [coefficient of variation (CV) 6.2%] compared with the prekinetic procedure (CV 14.6%).

CONCLUSIONS

Although the two methods differ considerably in their approach, clamping of BrAC resulted in more accurate alcohol levels than infusion based on PK modelling and does not require an extra prestudy occasion. The novel alcohol clamping paradigm can be of value in future studies of alcohol interactions or the pharmacodynamics of acute alcohol administration.

Standardization of Alcohol Calculations in Research

BACKGROUND

Nonstandardized reporting of alcohol consumption, definitions of what constitutes a standard drink, and incomplete dosing or estimates of intoxication are common problems in many areas of alcohol research. To enhance communication among scientists and to make interpretation of results more accurate and meaningful, researchers need to apply systematically current scientific principles in calculating drinks, doses, and alcohol concentrations. Basic formulas are compiled and explained to assist alcohol researchers and standardize the reporting and interpretation of alcohol data.

METHODS

Basic alcohol calculations are reviewed, and 20 mathematical calculations in alcohol pharmacokinetics and pharmacology are derived. Examples of how each calculation works are presented.

RESULTS

The formulas presented enable researchers to calculate accurately and systematically the amount of alcohol in any beverage and estimate the blood alcohol concentration in a range of subjects with individual characteristics and drinking patterns.

CONCLUSIONS

Accurate estimates of alcohol use and intoxication are important in many areas of research. Applying standards to the way alcohol is measured and interpreted enables better communication, more accurate analyses, and, in some cases, may impact the interpretation of results. Regardless of the field of study, alcohol researchers are encouraged to and can apply uniform standards in measuring alcohol consumption and estimating the effects of alcohol using the scientific methodologies described.

Neuroimaging of Rodent and Primate Models of Alcoholism: Initial Reports From the Integrative Neuroscience Initiative on Alcoholism

Neuroimaging of animal models of alcoholism offers a unique path for translational research to the human condition. Animal models permit manipulation of variables that are uncontrollable in clinical, human investigation. This symposium, which took place at the annual meeting of the Research Society on Alcoholism in Vancouver, British Columbia, Canada, on June 29th, 2004, presented initial findings based on neuroimaging studies from the two centers of the Integrative Neuroscience Initiative on Alcoholism funded by the National Institute on Alcohol Abuse and Alcoholism. Effects of alcohol exposure were assessed with in vitro glucose metabolic imaging of rat brain, in vitro receptor imaging of monkey brain, in vivo magnetic resonance imaging of monkey brain, and in vivo magnetic resonance spectroscopic quantification of alcohol metabolism kinetics in rat brain.

Population Pharmacokinetics of Ethanol in Drinking Drivers Using Breath Measures

This study was undertaken to evaluate the population pharmacokinetic behavior of ethanol from breath ethanol measures and to see if these results could be used to establish the drinking history of our drinking drivers. The population consisted of 55 self-identified light to heavy drinkers. All had been arrested at least once for driving under the influence of alcohol. Sixteen were women, and 39 were men. Breath was analyzed for ethanol using a 3-wavelength infrared spectrophotometer. An iterative 2-stage Bayesian (IT2B) parametric modeling program was used first to obtain gamma, a measure of the relative magnitude of the intraindividual variability. The nonparametric adaptive grid (NPAG) maximum likelihood program, using gamma, was then used to obtain the full nonparametric joint parameter density. A 2-compartment Michaelis-Menten model was evaluated. The 2-compartment model gave a gamma of 1.75. Thus, the standard deviation (SD) of the nonassay sources of intraindividual variability was 1.75 times the SD of the assay itself for the 2-compartment model. The NPAG program gave the following means, medians, modes, and standard deviations for the 2-compartment model: ka (h(-1)) = 6.43, 5.46, 2.93, 4.58; Vmax (g/h) = 12.09, 11.90, 13.03, 3.73; Km (g/L) = 0.1273, 0.1367, 0.1991, 0.0528; Vc (L) = 31.32, 29.30, 24.88, 10.52; kcp (h(-1)) = 4.38, 1.30, 1.12, 6.16; and kpc (h(-1)) = 9.11, 2.47, 0.89, 8.98. These drinking drivers had a rate of metabolism of ethanol that was between that of moderate drinkers and confirmed alcoholics. Properly collected breath ethanol measures can be useful in a therapeutic drug-monitoring situation to obtain quick, accurate, and reliable measures of a patient's ethanol concentrations.

A revised pharmacokinetic model for alcohol

OBJECTIVE

To correct a defect in widely utilised pharmacokinetic models of alcohol absorption into the blood.

METHODS

The implications of the defect are briefly described. A highly simplified model that corrects this defect is then proposed, and the resulting differential equation describing blood-alcohol concentration from ingestion to elimination is derived. The equation is solved in closed form.

RESULTS

The improved model assumes that diffusion of alcohol across the interface between the stomach/intestine complex and the remaining body fluids (including blood plasma) is linearly proportional to the difference in alcohol concentration across the interface. The resulting equation is tested against experimental data with excellent agreement.

CONCLUSIONS

This model enables inferences to be drawn that are not possible with the more conventional model.

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.

Gender differences in alcohol metabolism: relationship to liver volume and effect of adjusting for body mass

BACKGROUND & AIMS

Alcoholic liver disease purportedly develops more readily in women than in men. Some studies have demonstrated faster rates of alcohol elimination in women. This study examined whether gender differences in alcohol metabolism are related to differences in liver volume and/or differences in lean body mass.

METHODS

Ten men and 10 women had alcohol elimination rates determined by clamping of the breath alcohol concentration at 50 mg/dL by means of a constant rate of intravenous infusion of 6% ethanol. Liver volume was determined by computed tomography.

RESULTS

Mean alcohol elimination rate and mean computed liver volume were not significantly different in men and women. Lean body mass was 42% greater in men than in women. Consequently, the calculated alcohol elimination rate and liver volume per kilogram of lean body mass were 33% and 38% higher in women than in men, respectively. When the alcohol elimination rate was calculated per unit liver volume, no gender-related difference was found.

CONCLUSIONS

Women have greater clearance of ethanol per unit lean body mass, confirming previous oral alcohol administration studies. Women have approximately the same liver volume as men, explaining the equivalent alcohol elimination rates seen when men and women are compared on the basis of liver size.

Arterio-venous ethanol levels in blood and plasma after intravenous injection in rabbits

Arterio-venous ethanol concentrations in both whole blood and plasma were determined as a function of time in the rabbit. Following i.v. injection of 1.0 g/kg, both arterial and venous ethanol concentrations showed an abrupt decline occurring immediately after the end of the administration, followed by a pseudolinear phase that persisted for the length of the experiment. This work substantiates the arterio-venous ethanol concentration differences reported in the literature. It illustrates that equal arterial and venous ethanol concentrations may not be achieved readily after rapid i.v. injection. Moreover, it demonstrates a faster decay of ethanol concentrations in arterial than in venous plasma.

Effects of opioids on the absorption of alcohol

Administration of opiate agonists and antagonists has been shown to increase and decrease alcohol consumption, respectively. Because opioids can affect gastric emptying and decrease intestinal motility, the present experiments were done to determine whether changes in alcohol consumption following opioid administration might be due to opioid-induced changes in the pharmacokinetics of alcohol. In experiment 1, morphine in doses ranging from 1.5 to 4.5 mg/kg dose dependently decreased the absorption of alcohol induced by oral intubation (1 g/kg) and reduced peak blood alcohol levels (BALs). Naltrexone in doses ranging from 1.5 to 4.5 mg/kg produced a small, but significant, reduction in the absorption of alcohol, but the effects were not dose related. Similar effects of morphine and naltrexone on alcohol absorption were observed in rats infused with alcohol (1 g/kg) through an implanted intragastric cannula. The effects of morphine on alcohol absorption were observed whether alcohol levels were determined from tail vein or arterial blood samples or from brain samples. The effects of morphine on alcohol absorption were not blocked by pretreatment with methyl-naltrexone. However, the peripherally acting opioid agonist loperamide reduced BALs in a manner similar to morphine. These studies indicate that although opiate agonists and antagonists modify alcohol absorption to different extents, their effects on BALs are not a sufficient condition to induce changes in alcohol consumption.

Gender and alcohol dosing: a procedure for producing comparable breath alcohol curves for men and women

Gender differences in peak breath alcohol concentrations (BrACs) reached in alcohol administration studies can make the interpretation of study findings difficult. This study evaluated the CBAC computer program as a way of minimizing gender differences in the BrAC curve. After consuming a predrink meal that was adjusted by body mass, 31 female and 27 male subjects consumed an alcoholic beverage targeted for either 0.04% or 0.08%. Mean peak BrACs for women and men were not significantly different. Similarly, the four BrAC readings obtained over the first 2 hr postdrink showed no gender differences. A dose x gender interaction was observed on time to peak BrAC, with women reaching peak BrAC faster than men only in the high dose groups. By decreasing gender differences in BrAC curves, this dosing procedure can aid in reducing the potential confound of dose and gender.

Ethnic differences in gastric sigma-alcohol dehydrogenase activity and ethanol first-pass metabolism

We assessed whether the low sigma-alcohol dehydrogenase (ADH) activity in Japanese (compared with Caucasians) affects the first-pass metabolism of ethanol. ADH isozyme activities were determined in endoscopic biopsies of the gastric corpus from 24 Japanese and 41 Caucasian men by starch gel electrophoresis and by comparing the reduction of m-nitrobenzaldehyde (a preferred substrate of sigma-ADH) with that of acetaldehyde (a preferred substrate of gamma-ADH) and the glutathione-dependent formaldehyde oxidation (a specific reaction of chi-ADH). Alcohol pharmacokinetics was compared in 10 Japanese and 10 Caucasians after administration of ethanol (300 mg/kg of body weight) intravenously or orally, using 5 and 40% oral solutions. Japanese exhibited lower sigma-ADH activity than Caucasians, with no difference in the other gastric isozymes. With 5% ethanol, first-pass metabolism was strikingly lower in Japanese than in Caucasians. Blood alcohol levels were similar because of the high elimination rate in Japanese due to the hepatic beta 2-ADH variant. With 40% ethanol, the first-pass metabolism increased in both groups to comparable levels, suggesting an additional contribution by chi-ADH at high ethanol concentrations. These results indicate that sigma-ADH activity contributes significantly to gastric ethanol oxidation and its lower activity in Japanese is associated with lesser first-pass metabolism.

Kinetic interactions between 4-methylpyrazole and ethanol in healthy humans

4-Methylpyrazole (4-MP), a potent inhibitor of alcohol dehydrogenase activity, is a candidate to replace ethanol as the antidote for methanol and ethylene glycol intoxications, because it has a longer duration of action and apparently fewer adverse effects. To study a probable mutual inhibitory effect between ethanol and 4-MP on their elimination, two studies were performed in healthy human volunteers using double-blind crossover designs. In study A1 4-MP in the presumed therapeutic dose range of 10 to 20 mg/kg caused a 40% reduction in the rate of elimination of ethanol in 12 subjects given 0.5 to 0.7 g/kg of ethanol. These data suggest that such doses of 4-MP inhibit alcohol dehydrogenase activity in humans in vivo and would be effective at blocking methanol or ethylene glycol metabolism. In study B, ethanol (0.6 g/kg followed by 0.2 g/kg twice) significantly decreased the rate of elimination of 4-MP (5 mg/kg, given intravenously to four subjects). These moderate doses of ethanol also inhibited the rate of urinary excretion of 4-carboxypyrazole, the primary metabolite of 4-MP in humans. Data suggest that ethanol inhibits 4-MP metabolism, thereby increasing the duration of therapeutic blood levels of 4-MP in the body. This mutual interaction may have clinical implications, because most self-poisoned patients have also ingested ethanol. Theoretically, methanol and ethylene glycol might also show such interactions with 4-MP.

Time-dependent quantifiable withdrawal from ethanol in the rat: effect of method of dependence induction

The importance of temporal factors on the presence and severity of ethanol withdrawal signs in the rat was quantified using rating scale, tremor, and acoustic startle paradigms. Ethanol dependence was induced in naive male Wistar rats by liquid diet administration (n = 21) or vapor inhalation (n = 13). Subjects were analyzed for intensity and duration of physiological ethanol dependence in repeated-measures trials conducted over 72 h post-ethanol withdrawal. Indices of dependence included CNS hyperexcitability manifested as observable withdrawal signs increased acoustic startle reactivity, and tremor activity. Data analysis revealed that withdrawal signs, observed and elicited, generally reached peak intensities between 12 and 24 h postwithdrawal and were more readily observed following vapor inhalation than liquid diet administration, probably because of the higher BALs attained with the inhalation procedure. Results suggest a difference in time course observed with the different behavioral paradigms. In particular, a possible sensitization to startle stimuli was exhibited independent of both startle intensity and dependence induction method. The neural substrates governing these behavioral time course differences remain to be determined.

Evaluation of the Alcopatch, a transdermal dosimeter for monitoring alcohol consumption

BACKGROUND

The Alcopatch is an improved transdermal dosimeter for the measurement of alcohol consumption, by detection of ethanol in fluid excreted from the skin. The device is worn as a band around the ankle and provides a visual signal in the event of tampering.

METHODS

Fourteen volunteers wore duplicate Alcopatches for a period of 7 or 8 days, while keeping a written record of their beverage alcohol consumption. Ethanol concentration in the Alcopatch was measured by gas chromatography and correlated with self-reported consumption.

RESULTS

All alcohol consumption in excess of 0.25 g/kg/day resulted in measurable levels of ethanol in the Alcopatch. A positive correlation was observed between the reported consumption of ethanol (in g/kg/day) and the concentration of ethanol in the Alcopatch (square root, in mg/dl) (y = 0.91x + 0.28, r = 0.61) in 12 of 14 subjects.

CONCLUSIONS

The Alcopatch detected the consumption of beverage alcohol with high sensitivity and specificity over a period of 7 to 8 days and may be useful for the study of target populations.

First-pass metabolism of alcohol. Absence of diurnal variation and its inhibition by cimetidine after evening meal

To determine whether the first-pass metabolism (FPM) of orally consumed alcohol varies with the time of day, 12 healthy male subjects were tested with both oral and intravenous alcohol (0.3 g/kg), in the morning and evening, always 1 hr after the same standard meal. The results revealed no significant differences in FPM (81.6 +/- 11.6 vs 92.8 +/- 10.6 mg/kg) or in any other index of alcohol absorption and metabolism. Eleven subjects were also tested in the evening after treatment with cimetidine, an H2-antagonist that inhibits gastric alcohol dehydrogenase activity in vitro. Compared to baseline, cimetidine (1 g/day for eight days) significantly decreased FPM (from 100.1 +/- 8.0 to 52.6 +/- 11.4 mg/kg, P < 0.01) and increased the systemic bioavailability of alcohol (from 66 +/- 3 to 82 +/- 4%, P < 0.01), as well as peak blood alcohol concentrations (from 4.3 +/- 0.4 to 5.9 +/- 0.5 mM, P < 0.05) and areas under the curve (from 5.1 +/- 0.5 to 7.0 +/- 0.5 mM/hr, P < 0.01). The results indicate the absence of diurnal variation in FPM and suggest that patients given cimetidine should be warned of its possible interaction with alcohol regardless of the time of day.

Computer simulation analysis of blood alcohol

A mathematical model using an iterative algorithm based on the Widmark formula is used to simulate a continuous spectrum of the expected blood alcohol concentration from start of alcohol dosage to time of specific event in numerical and graphic form. Absorption is based on flexible first order rates with provision for an optional good-fit model of the delaying effect of food. Elimination is based initially on selectable zero order rates followed by first order kinetics at low blood alcohol concentrations. A correlation coefficient of 0.94 was obtained in comparisons of projected to observed blood alcohol concentrations. A measurement of the area under the curve is provided. The software program utilizing the algorithm is suitable for forensic and clinical applications.

Significant increase of blood alcohol by cimetidine after repetitive drinking of small alcohol doses

To assess effects of repetitive alcohol drinking and pre-existing first-pass metabolism on the cimetidine-induced increase in blood alcohol concentrations, 20 healthy men (aged 20 to 40) of varied ethnicity and consuming less than 60 g alcohol per week underwent baseline quantitation of first-pass metabolism of alcohol. This was followed by oral administration of 0.6 g/kg ethanol given postprandially in 3 to 4 drinks spread over 135 min, before and after cimetidine (400 mg twice a day for 7 days). Blood alcohol concentrations were determined by breath analysis. First-pass metabolism was quantified by applying Michaelis-Menten kinetics to blood alcohol curves after intravenous or oral administration of equal alcohol doses. At baseline, 15 subjects had a substantial first-pass metabolism (over one sixth of the dose); their alcohol levels increased with repeated doses with a mean peak of 27 +/- 3 mg/dl before and 39 +/- 5 after cimetidine (P < 0.01), an effect much greater and longer than after a single alcohol dose. Three subjects exceeded 50 mg/dl, the legal limit for driving in several countries. By contrast, in the five subjects with minimal first-pass metabolism, cimetidine did not increase alcohol levels. Thus, under conditions mimicking social drinking, cimetidine increased blood alcohol to concentrations known to impair psychomotor skills and they persisted at those levels over prolonged periods of time. In a minority of subjects, no such interaction was found, but their first-pass metabolism at baseline was absent or minimal and thus no inhibition by the drug was to be expected.

Variability of ethanol absorption and breath concentrations during a large-scale alcohol administration study

Ethanol disposition was evaluated in 77 female and 97 male college seniors during an alcohol challenge study. All were regular drinkers who exceeded legal intoxication levels at least twice a month by history. A standard ethanol dose (females, 0.43 g/kg; males, 0.51 g/kg) was administered over 10 min, after a 4-hr fast, and breath alcohol concentrations (BrACs) were measured for 2 hr. Intersubject variability in BrACs was greatest early in the study, during ethanol absorption; the coefficient of variation decreased from 39% at 14 min to 14% at 125 min after the start of drinking. The time to peak BrAC varied from 10 to 91 min after the start of drinking (mean 39.6 min). Mean BrACs were significantly lower in females than males; mean peak BrACs were 0.054 g/210 liters in females and 0.058 g/210 liters in males (p = 0.031). The beta- and r-values for both genders were higher than those typically used in ethanol dose calculation formulas. Data are discussed to direct future research. The constants used in Widmark's formula need to be revised differentially for males and females in this population to reach specific target BrACs. Furthermore, substantial variability in absorption rates must be accounted for when assessing rising versus falling limb BrAC phenomena.

The effects of acute stress on ethanol absorption in LS and SS mice

Previously, our laboratory demonstrated that naive long-sleep (LS) mice absorb ethanol faster than short-sleep (SS) mice when administered 6.0 g/kg ethanol intragastrically (IG). We also demonstrated that the removal of the adrenal glands results in decreased absorption in both lines of mouse. The present study was designed to assess whether acute short-term elevations of corticosterone produced by exposure to a mild stressor could also alter ethanol absorption in LS and SS mice. Because a difference in ethanol absorption rates was observed in LS mice as a function of time of day, all stress experiments were performed in the morning. CCS elevation was induced by exposure to an elevated plus-maze for 45 min. LS mice demonstrated greater CCS release in response to this stressor than SS mice. This exposure to a mild stressor produced an increase in ethanol absorption in both lines of mice receiving a 6.0 g/kg intragastric dose of ethanol. Although this effect of stress on ethanol absorption could be prevented by adrenalectomy in SS mice, adrenalectomy alone did not completely block these effects of stress on ethanol absorption in LS mice. Dexamethasome treatment at the time of adrenalectomy was required to block the effects of stress on ethanol absorption in LS mice. These results suggest that exposure to mild stressors may alter ethanol pharmacokinetic parameters but that genetic factors may play a role in this response via regulation of the hypothalamic-pituitary-adrenal axis.

Indexing withdrawal in mice: matching genotypes for exposure in studies using ethanol vapor inhalation

Withdrawal Seizure-Prone (WSP) and -Resistant (WSR) mice have been bidirectionally selected for severity of handling-induced convulsions (HIC) following withdrawal from 72 hr of chronic ethanol vapor inhalation. During selection, daily injections of the alcohol dehydrogenase inhibitor, pyrazole, were used to enhance and stabilize blood ethanol concentrations (BEC). After 26 generations of selection, WSR mice show lower withdrawal BEC than WSP mice exposed to the same ethanol vapor concentrations. Because it is desirable to compare mice maintained at the same BEC to assess correlated responses to selection, this has necessitated exposing WSR mice to higher ethanol vapor concentrations than WSP mice to achieve matched chronic BEC. The experiments reported herein demonstrate two methods for producing matched withdrawal BEC: (1) by exposing mice to the same ethanol vapor concentration and varying the pyrazole dose; and (2) by administering only ethanol at different vapor concentrations and selecting some mice with approximately the same BEC. When exposed to the same ethanol vapor concentration, WSR mice given 1.0 mmol/kg pyrazole had withdrawal BEC equivalent to WSP mice given 0.75 mmol/kg pyrazole. However, WSP mice had much more severe withdrawal HIC than WSR mice. WSP and WSR mice metabolized ethanol at the same rate following withdrawal. The basis for the differential effectiveness of pyrazole is unknown. We also exposed mice to higher ethanol vapor concentrations in the absence of pyrazole. By exposing WSR mice to higher concentrations than WSP, roughly equivalent BEC on withdrawal was achieved. Because BEC are more variable in the absence of pyrazole, it was necessary to select animals of each genotype to achieve relatively matched BEC.(ABSTRACT TRUNCATED AT 250 WORDS)