Male vs Female Metabolism of Alcohol in the DUI Case

It has been known to DUI lawyers for some time that women are generally more susceptible to the effects of alcohol than men. This has generally been explained by pointing out that women are smaller and have relatively more fat and less water than men. But recent research seems to indicate that a more important reason may be that women have significantly lower amounts of an enzyme that provides a protective barrier in the stomach by breaking alcohol down before it circulates into the body.

An article appearing in the Los Angeles Times, Jan. 11, 1990, at A27, recounted how scientists at the University School of Medicine in Trieste, Italy, and the Veterans Affairs Medical Center, Bronx, New York, found that the stomach lining contains an enzyme called gastric alcohol dehydrogenase that breaks down alcohol. To determine the effects of the enzyme, they administered alcohol both orally and intravenously (i.e., bypassing the stomach) to a group of 14 nonalcoholic men, 6 alcoholic men, 17 nonalcoholic women, and 6 alcoholic women.

There were two interesting results. First, in both the nonalcoholic and alcoholic groups, women had higher blood-alcohol concentrations than men after ingesting an equivalent dose of ethanol; by contrast, there were no differences when the ethanol was taken intravenously. With weight differences taken into account, the researchers found that women became legally intoxicated after consuming 20 to 30 percent less alcohol than men; absent allowance for weight, an average-size woman reaches a given blood-alcohol level after consuming about 50 percent less alcohol than a man consumes to reach that level.

Second, the alcoholic men and women had significantly higher BAC levels after oral ingestion than the nonalcoholic men and women; the levels reached by alcoholic women indicated a nearly total absence of the protective enzyme in their stomachs.

The scientists concluded that legislatures may need to consider sex differences when defining safe levels of drinking for DUI purposes. Although they did not address the issue, the findings concerning alcoholics would also seem to pose some interesting DUI legal and factual issues. For a further discussion of the study, see Frezza and Lieber, High Blood Alcohol Levels in Women: The Role of Decreased Gastric Alcohol Dehydrogenase Activity and First-Pass Metabolism, 322(2) New England Journal of Medicine 95 (1990).

An article in the Canadian Society of Forensic Science journal has reported a finding that [women taking oral contraceptive steroids (O.C.S.) appeared to eliminate ethanol significantly faster than women not taking O.C.S. Papple, The Effect of Oral Contraceptive Steroids (O.C.S.) on the Rate of Post-Absorptive Phase Decline of Blood Alcohol Concentration in the Adult Woman, 15:1 Canadian Society of Forensic Science journal at 17 (1982).

The purpose of the study was to determine whether there was an interaction between O.C.S. and the metabolism of ethanol. The study compared females taking O.C.S. with males and with females not taking O.C.S. In addition, the study took into account the four phases of a woman's menstrual cycle for females taking O.C.S. and those not taking O.C.S.

The study found that O.C.S. stimulate the elimination of ethanol from the human bloodstream. The study also concludes that the position of the women in their menstrual cycle was not the determining factor in the difference in the ethanol elimination rate. More specifically, the study presented the following conclusions: No significant difference was seen in the rate of decline of BAG in women not taking O.C.S. compared to men, and a highly significant increase in the rate of decline was noted in women who were taking O.C.S.

Thus, if the expert witness in a DUI case attempts to estimate the alcohol concentration of the female at the time of driving, use of a standard elimination rate (e.g., 15 mg percent per hour) will result in a faulty extrapolation if the woman was taking oral contraceptive steroids.

Yet another example of sex difference in blood-alcohol analysiswas uncovered in a study by Jeavons and Zeiner, Effects of Elevated Female Sex Steroids on Ethanol and Acetaldehyde Metabolism in Humans, 8(4) Alcoholism: Clinical and Experimental Research 352 (1984). This article revealed that women who were taking oral contraceptives and women who were pregnant had elevated acetaldehyde levels. Apparently, the ability to metabolize acetaldehyde decreases as the level of sex steroids increases. Put another way, women with a greater amount of sex steroids in their systems will also have a greater amount of acetaldehyde. Such women who take breath tests will also have inaccurately high blood-alcohol readings in DUI cases.

In an article entitled Determination of Liquid/Air Partition Coefficients for Dilute Solutions of Ethanol in Water, Whole Blood, and Plasma, published in journal of Analytical Toxicology 193-197 (July/August 1983), Dr. A. W. Jones discusses an experiment comparing the blood/air ratio of men and women, concluding that the sexes have different ratios. Breath testing devices used in DUI investigations are calibrated based on an assumed blood/breath ratio of 2100 to 1 - an average for men. The Swedish experiments, however, would seem to indicate that a woman with a given blood-alcohol reading on a breath testing device may actually have a lower level than would a man with the same reading.

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