Abstract
The demethylation of morphine and a number of other compounds by a rat liver microsome preparation is described. A concentration of 40 mM nicotinamide was necessary in the system to obtain the optimal rate of demethylation. Only N-methyl compounds of plant or synthetic origin were demethylated while those which occur naturally in mammalian tissues were not demethylated. Nalorphine and levallorphan inhibited the demethylation of morphine. The administration of either morphine or cortisone caused a significant diminution in the demethylation of morphine.