From a modeling perspective, the elimination of ethanol at lower concentrations follows first-order elimination kinetics, where the elimination rate increases linearly with rising alcohol concentration. However, this phase is limited because ADH enzymes become saturated at a BAC of around 0.15 g/L (81), roughly the level achieved after drinking less than one standard drink. Once saturation occurs, elimination shifts to zero-order kinetics, meaning alcohol is removed at a constant rate regardless of BAC (4). In this phase, hepatic metabolism is limited by the intrinsic blood flow to the liver. Since alcohol delivery via blood flow to the liver exceeds the metabolic rate, BAC can remain high and increase disproportionately with dose, potentially leading to fatal alcohol poisoning.
