Interactions of narcotics and their antagonists with human serum esterase. VI: The behavior of 14-hydroxylated morphine derivatives.

Study of the interaction of 14-hydroxylated morphines and morphinans with human serum esterase revealed behavior similar to that of other morphine derivates as shown by similar acceleratory efficacies and affinity constants. However, 14-hydroxydihydro-6-morphinones showed anomalously low apparent affinities and anomalously high apparent efficacies, while at the same time seemingly interfering with the attachment of another drug to the enzyme. These anomalies are satisfactorily explained by assuming a second receptor site for which only the hydroxyketones have affinity and which interacts with the receptor site common to all opiates and opiate antagonists. Equations derived from this assumption allow to determine the parameters of the interactions of drugs with both receptor sites.