Alcohol, Chemistry and You
Distribution of Ethyl Alcohol in the Body
Dr. Bill Boggan

Problems

Case Study
 

Chemistry and Mathematics

The concentration curves shown here, relating the alcohol content of the body with time and the alcohol content of the tissue with that of the brain, are abstractions and representations. We do not see any chemicals, nor do we see chemical formulas. But what we do see is a representation of a dynamic chemical process. If we increase alcohol levels in the body, the alcohol quickly gets to the brain and but slowly leaves.

Ethyl alcohol distributes in the body in proportion to the water content in the particular tissue. As indicated, ethyl alcohol gets into the body by absorption, however this is a slow process. To distribute alcohol throughout the body by absorption alone would take a long time. However, ethyl alcohol crosses with water into the blood stream, therefore the process of distribution of alcohol is rapidly speeded up. In addition it would be expected that the more one drinks, the more alcohol would be in the blood.

Since ethyl alcohol mixes freely with water it would be expected that even within the blood, alcohol distribution would parallel the distribution of water in the blood. This has been studied by several research groups (e. g. Hodgson and Shajani, 1985; Winek and Carfagna, 1987; Jones et al, 1990, 1992). Since plasma and serum have approximately the same water content (92%), whereas whole blood has about 80% water, it would be expected that the ratio of ethyl alcohol content in the plasma or serum to alcohol content in whole blood would be equal to the ratio of water in plasma to the water in whole blood. This is what was found, in that the ratio was approximately 1.12 for both (92%/80% = 1.15). Since water diffuses easily across cell membranes through aqueous channels, including vascular endothelium ( ) it is expected that ethyl alcohol would do the same. Further it is expected that the ethyl alcohol concentration in the tissues would rapidly reach equilibrium with the ethyl alcohol in the blood. This is certainly been found to be the case.

It is important to note that the rate of attainment of the equilibrium depends upon the ratio between the tissue water content and the minute-volume blood flow to the tissue, i.e. how much blood flows per unit of time. Tissues with lower blood flow rates such as resting muscle, adipose (fat) tissue, and skin require longer to reach equilibrium with the blood and differences between concentrations in the arteries and the veins will last longer. (Remember arteries take blood to the tissues, while veins take blood away). In contrast tissues with higher blood flow such as the brain, kidney, and lung will attain equilibrium more rapidly and arteriovenous differences will be of short duration.

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