Pharmacokinetics of ethanol in plasma and whole blood: estimation of total body water by the dilution principle

Distribution ratios of ethanol and water between whole blood, plasma, serum, and erythrocytes: Recommendations for interpreting clinical laboratory results in a legal context

This article reviews the scientific literature dealing with the distribution of ethanol and water between whole blood (WB), plasma, serum, and erythrocytes (red-blood cells). Knowledge of the ethanol distribution ratio is important when analytical results derived from hospital clinical laboratories are interpreted in a forensic context, such as during the prosecution of traffic offenders. Statutory blood-alcohol concentration (BAC) limits for driving are defined as the concentration of ethanol in WB and not in plasma, serum or red-blood cells. These bio-fluids differ in their water content and thereby the concentrations of ethanol. Plasma and serum contain ~90%-92% w/w water, WB ~78%-80% w/w and erythrocytes ~64%-66% w/w. The mean plasma/WB and serum/WB distribution ratios of ethanol are therefore expected to be ~1.15:1 (91/79 = 1.15), which is in good agreement with values determined empirically. However, in individual cases, the actual distribution ratio will depend on the person's age, gender, and biochemical and hematological properties of the blood specimen, such as its hematocrit. For legal purposes, we recommend that the concentration of ethanol in plasma or serum determined at hospital laboratories is divided by a factor of 1.2, which would provide a conservative estimate of the co-existing BAC and the chance of overestimating the true value is only 1 in 2000 (0.05%).

Syndecan-1 and Glypican-1 Knockout Alters Body Water Balance and Urine Response to Fluid Challenge in Mice

Syndecan-1 (Sdc-1) and glypican-1 (Gpc-1) are 2 important proteoglycans found in the glycocalyx and believed to govern transvascular distribution of fluid and protein. In this translational study, we assessed Sdc-1 and Gpc-1 knockout (KO) on whole body water balance after an intravenous volume challenge. Sdc-1 and Gpc-1 KO mice had higher starting blood water content versus strain-matched controls. Sdc-1 KO mice exhibited a significantly higher diuretic response (87%; p < 0.05), higher excreted volume/infusion volume ratio (p < 0.01), higher extravascular/infused ratio, and greater tissue water concentration (60 vs. 52%). Collectively, these suggest differences in kidney response and greater fluid efflux from peripheral vessels. The CD1 strain and Gpc-1 KO had a 2-3-fold larger urine output relative to C57 strain, but Gpc-1 KO reduced the excreted/infused ratio relative to controls (p < 0.01) and they maintained plasma dilution longer. Thus, genetic KO of Sdc-1 and Gpc-1 resulted in markedly different phenotypes. This work establishes the feasibility of performing fluid balance studies in mice.

Evidence based survey of the distribution volume of ethanol: Comparison of empirically determined values with anthropometric measures

The Widmark equation is commonly used when blood alcohol calculations are required in forensic and legal medicine, such as in road-traffic cases and alcohol-related deaths. An important biological variable in this connection is the volume of distribution (V_d) of ethanol, which is commonly referred to as the rho-factor. Although a person's V_d can be determined empirically through controlled drinking experiments, this approach is not very practical in reality. For this reason, a number of anthropometric equations have been developed that utilize sex, age, height and weight to estimate the person's total body water (TBW) and hence V_d of ethanol. To date, there are not any studies that compare V_d derived from anthropometric data with robust values measured empirically. From the literature we compiled information about the V_d of ethanol from drinking studies with 173 Caucasian males and 63 Caucasian females from Western Europe. These empirically derived values of V_d were then compared with estimates derived from various anthropometric equations. In males the Watson, Watson and Batt regression equation involving age, height and weight gave the most accurate results (bias was 0.00L/kg) and 95% range ±0.13L/kg. The equation derived by Forrest, which took into consideration a person's body mass index (BMI), gave the best estimates of V_d for females; mean bias -0.01L/kg and range ±0.15L/kg.

Impact of Trauma, Massive Blood Loss and Administration of Resuscitation Fluids on a Person's Blood-Alcohol Concentration and Rate of Ethanol Metabolism

Excessive drinking and drunkenness are tightly linked to many types of intentional and unintentional injuries involving trauma and blood loss, which often necessitate emergency medical intervention. This article considers the impact of trauma, massive blood loss, and the administration of life-saving replacement fluids on a person's blood alcohol concentration (BAC) and rate of ethanol metabolism. Both German and English language journals were reviewed and results from animal experiments, human studies, and actual victims of trauma undergoing life-saving treatment were considered. If trauma-related bleeding occurs when some ingested alcohol remains unabsorbed in the stomach, then under these circumstances continued absorption into portal venous blood is delayed, owing to altered splanchnic circulation. Hemodilution caused by administration of replacement fluids has only minimal effects on a preexisting BAC, because ethanol distributes into the total body water (TBW) compartment, which represents 50-60% of body weight. After hypovolemia there is a transfer of fluids from tissue compartments into the blood, which becomes more like plasma in composition with lower hematocrit and hemoglobin content. Unless the trauma or emergency treatment impedes hepatic blood flow, the rate of ethanol metabolism is not expected to differ from normal values, namely 0.10-0.25 g/L/h (0.01-0.025 g% per h). If ethanol is fully absorbed and distributed in all body fluids and tissues, neither massive blood loss nor administration of resuscitating fluids is expected to have any significant effect on a preexisting BAC or the rate of ethanol metabolism.

Convective transport of highly plasma protein bound drugs facilitates direct penetration into deep tissues after topical application

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Many products are applied to human skin for local effects in deeper tissues. Animal studies suggest that deep dermal and/or subcutaneous delivery may be facilitated by both dermal diffusion and transport via the cutaneous vasculature. However, the relationship between the extent and pathways of penetration, drug physicochemical properties and deeper tissue physiology is not well understood.

WHAT THIS STUDY ADDS

We have used a physiologically based pharmacokinetic model to analyze published human cutaneous microdialysis data, complemented by our own in vitro skin penetration studies. We found that convective blood, lymphatic and interstitial flow led to significant deep tissue concentrations for drugs that are highly plasma protein bound. In such cases, deeper tissue concentrations will occur earlier and may be several orders of magnitude greater than predicted by passive dermal diffusion alone.

AIMS

To relate the varying dermal, subcutaneous and muscle microdialysate concentrations found in man after topical application to the nature of the drug applied and to the underlying physiology.

METHODS

We developed a physiologically based pharmacokinetic model in which transport to deeper tissues was determined by tissue diffusion, blood, lymphatic and intersitial flow transport and drug properties. The model was applied to interpret published human microdialysis data, estimated in vitro dermal diffusion and protein binding affinity of drugs that have been previously applied topically in vivo and measured in deep cutaneous tissues over time.

RESULTS

Deeper tissue microdialysis concentrations for various drugs in vivo vary widely. Here, we show that carriage by the blood to the deeper tissues below topical application sites facilitates the transport of highly plasma protein bound drugs that penetrate the skin, leading to rapid and significant concentrations in those tissues. Hence, the fractional concentration for the highly plasma protein bound diclofenac in deeper tissues is 0.79 times that in a probe 4.5 mm below a superficial probe whereas the corresponding fractional concentration for the poorly protein bound nicotine is 0.02. Their corresponding estimated in vivo lag times for appearance of the drugs in the deeper probes were 1.1 min for diclofenac and 30 min for nicotine.

CONCLUSIONS

Poorly plasma protein bound drugs are mainly transported to deeper tissues after topical application by tissue diffusion whereas the transport of highly plasma protein bound drugs is additionally facilitated by convective blood, lymphatic and interstitial transport to deep tissues.

Physiologically based pharmacokinetic (PBPK) models for ethanol

Physiologically based pharmacokinetic models have been used to describe the distribution and elimination of ethanol after intravenous administration. These models have been used to estimate the ethanol infusion profile that is sufficient for achieving a prescribed breath ethanol concentration time course in individuals, providing a useful platform for several pharmacokinetic and pharmacodynamic investigations. Mathematical foundations of these models are examined, including the derivation of an explicit set of governing equations in the form of a system of nonlinear ordinary differential equations. These equations can then be used to formulate and refine parameter identification and control strategies. Finally, a framework in which models related to this model can be constructed and analyzed is described.

Alterations in ethyl alcohol pharmacokinetics during oral consumption of malt liquor beverages in African Americans

BACKGROUND

Malt liquor (ML) beverages have become increasingly popular among urban minority groups, due partly to their inexpensive price and targeted advertising. We hypothesized that nonfermented by-products contained in ML beverages will alter the pharmacokinetics (PK) and pharmacodynamic (PD) effects of its ethanol content. In addition, we determined the effect of alcohol dehydrogenase (ADH) genotypes on the PK following consumption of ML beverages.

METHODS

The study was conducted in 31 healthy adult African-American social drinkers, mean +/- SD age of 22.3 +/- 1.3 years, and weight of 70.7 +/- 10.9 kg. Participants were administered ethanol, in randomized order, 2-weeks apart, in the form of oral ML beverage (6%v/v), or isocaloric solution of diet soda-ethanol (DS-Etoh) beverage (6%v/v). During each session the beverage was consumed over 4 minutes and breath alcohol concentrations (BrAC) as well as subjective and behavioral effects of ethanol were evaluated over 180 minutes. Pharmacokinetic parameters of ethanol were calculated using Michaelis-Menten elimination kinetics. The effect of ML and ADH genotype on PK was evaluated using the Wilcoxon rank-sum test and the Wilcoxon signed rank test, respectively.

RESULTS

Results show a slower mean rate of absorption, K(a), (0.12 vs. 0.15 min(-1), p = 0.03) and a longer time to reach maximum concentration, T(max), (28 vs. 23 minute, p < 0.01) for the ML compared with DS-Etoh beverage. The ML beverage resulted in a larger area under the BrAC-time curve compared with DS-Etoh beverage (8.4 vs. 6.8 min g/dl, p = 0.02). There was no difference in the subjective PD effects between the 2 beverages.

CONCLUSION

Results show that exposure to ethanol following the consumption of ML beverages is different compared to that following nonmalt beverages in African-Americans. These differences may be related to nonfermented by-products present in commercially available ML products. These PK differences do not appear to result in significant perceived alcohol PD changes, nor are they related to ADH genotype.

Faster absorption of ethanol and higher peak concentration in women after gastric bypass surgery

AIMS

To investigate the absorption, distribution and elimination of ethanol in women with abnormal gut as a result of gastric bypass surgery. Patients who undergo gastric bypass for morbid obesity complain of increased sensitivity to the effects of alcohol after the operation.

METHODS

Twelve healthy women operated for morbid obesity at least 3 years earlier were recruited. Twelve other women closely matched in terms of age and body mass index (BMI) served as the control group. After an overnight fast each subject drank 95% v/v ethanol (0.30 g kg-1 body weight) as a bolus dose. The ethanol was diluted with orange juice to 20% v/v and finished in 5 min. Specimens of venous blood were taken from an indwelling catheter before drinking started and every 10 min for up to 3.5 h post-dosing. The blood alcohol concentration (BAC) was determined by headspace gas chromatography.

RESULTS

The maximum blood-ethanol concentration (Cmax) was 0.741 +/- 0.211 g l-1 (+/- s.d.) in the operated group compared with 0.577 +/- 0.112 g l-1 in the controls (mean difference 0.164 g l-1, 95% confidence interval (CI) 0.021, 0.307). The median time to peak (tmax) was 10 min in the bypass patients compared with 30 min in controls (median difference -15 min (95% CI -10, -20 min). At 10 and 20 min post-dosing the BAC was higher in the bypass patients (P < 0.05) but not at 30 min and all later times (P > 0.05). Other pharmacokinetic parameters of ethanol were not significantly different between the two groups of women (P > 0.05).

CONCLUSIONS

The higher sensitivity to ethanol after gastric bypass surgery probably reflects the more rapid absorption of ethanol leading to higher Cmax and earlier tmax. The marked reduction in body weight after the operation might also be a factor to consider if the same absolute quantity of ethanol is consumed.