Ethanol interactions with other cytochrome P450 substrates including drugs, xenobiotics, and carcinogens

Chronic ethanol abuse is associated with increased activity of the microsomal ethanol-oxidizing system. This effect is due primarily to induction by ethanol of a specific cytochrome P450 (CYP2E1) responsible for enhanced oxidation of ethanol and other P450 substrates and, consequently, for metabolic tolerance to these substances. Furthermore, cytochrome 450 induction increases the activation of numerous xenobiotics to toxic metabolites and of chemical carcinogens to reactive metabolites, thereby accelerating their adverse effects. Microsomal enzyme induction has been associated with increased reactive oxygen species production and enhanced lipid peroxidation, as well as with decreased enzymatic and nonenzymatic scavenger activity, providing another possible explanation for ethanol-mediated toxicity. Yet another effect of chronic alcohol abuse is chronic immune system activation, which is the mechanism underlying alcohol-related liver disease. The metabolism of steroids and vitamins is catalyzed by P450 and is altered in chronic alcoholics. This article reviews recent advances in the understanding of ethanol interactions with drugs, toxic agents, and carcinogens, as well as with steroids and vitamins.