Inhibition by cyanide of drug oxidations in rat liver microsomes

Cyanide inhibited microsomal activities of aniline hydroxylation and aminopyrine, ethylmorphine and codeine demethylations and produced a modified type II difference spectrum of cytochrome P-450 to give two spectral dissociation constants, 0.21mM and 1.05 mM. The binding of cyanide to cytochrome P-450 resulted in innhibition of NADPH-cytochrome P-450 reductase activity. The cyanide inhibition of drug oxidations was partially avoided by increasing oxygen tension. A possible mechanism for the inhibition of drug oxidations by cyanide is discussed.