The influence of the body mass index (BMI) on the volume of distribution of ethanol

The volume of distribution of ethanol was already established in 1930s by Widmark. However, since then the average body composition has changed considerably. The effect of the body mass index (BMI) on the volume of distribution of ethanol was evaluated in this study. Fifty healthy volunteers (23 men and 27 women), with BMI-values between 16.0 and 36.0 kg/m2, were asked to drink a dose of 0.4 g ethanol per kilogram body weight after an overnight fast. The ethanol content was measured by a fully validated headspace-GC-FID method. The volume of distribution of ethanol varied between 0.40 and 0.68 L/kg for women, and between 0.43 and 0.73 L/kg for men. For both sexes, the volume of distribution decreased with increasing BMI. Regression analysis resulted in the following equations: volume of distribution = 0.8202 − 0.0090 × BMI for men (r = 0.66), and 0.7772 − 0.0099 × BMI for women (r = 0.78). Population probability prediction interval limits were also calculated. In view of the current study, fixed values for the volume of distribution of 0.7 L/kg and 0.6 L/kg for men and women, respectively, often applied in legal blood alcohol calculations, are mainly suited to judge underweight or normal weight people, but not obese persons.