The study evaluated the effects of a complex of oligomer proanthocyanidines derived from the crowns of the grapes Vitis vinifera on the oxidation of ethanol and on the activity of alcohol dehydrogenase and aldehyde dehydrogenase in the plasma of male volunteers given ethanol once, as well as in the rat liver during long-term alcohol use. Oligomer proanthocyanides were shown to be actively involved in the human and animal metabolism of ethyl alcohol in vivo. Under their action, the reductase activity was preserved, which prevented acetaldehyde from accumulating in the body since it reduces to less toxic ethanol. Oligomer proanthocyanidines from the crowns of the grape may be used to prevent a significant toxic effect of excess doses of ethyl alcohol on the body.