Demonstration of drug-ethanol interactions by changes in activity of hepatic microsomal oxidase/oxygenase cytochrome P-450 function.

"Uncoupling" of microsomal hepatic oxygenases is characterized by a situation in which microsomal monooxygenases exhibit more oxidase than oxygenase activity with an increased formation of hydrogen peroxide at the expense of O2, NADPH and substrate hydroxylation. The importance of such in vitro observations with respect to physiological conditions "in vivo" has been tested by investigating elimination kinetics of ethanol. If hexobarbital, a substrate of mixed function oxygenase as well as an "uncoupler", is given to guinea pigs together with ethanol, changes in the elimination of ethanol occur. It is suggested that this is the consequence of an increased formation of H2O2 which contributes via peroxidatic reaction of catalase to the elimination of ethanol. The results also show additional interactions of hexobarbital as well as of ethylmorphine with ethanol elimination. Both compounds increased the initial blood levels of ethanol which precede accelerated elimination, probably by a first pass effect. At low concentrations of ethanol, ethylmorphine inhibits ethanol elimination by inhibition of ADH.