Characterization of a common binding site for basic drugs on human alpha 1-acid glycoprotein (orosomucoid)

The interaction of chlorpromazine, DL-propranolol, and imipramine with isolated alpha 1-acid glycoprotein is characterized by relatively high association constants and only one binding site per protein molecule. The mutual displacement between the three drugs indicates that all three compounds are bound to the same binding site. Several other basic drugs from different pharmacological and chemical classes also displace chlorpromazine, DL-propranolol, and imipramine with potencies, one would predict from their association constants or from the degree of their plasma binding in humans. It is concluded that displacement phenomena like those observed in this study in vitro are likely to occur also in vivo.