A simple but highly sensitive radioreceptor assay for the determination of scopolamine and biperiden in human plasma.

Simple and sensitive methods are described for the determination of scopolamine and biperiden in human plasma. Each method consists of two steps. After extraction of scopolamine and biperiden with chloroform or n-hexane respectively and evaporation of the organic solvent, both drugs are determined by their ability to inhibit the specific binding of tritiated N-methyl-scopolamine to mouse brain homogenates. The lower limits of detection are plasma levels of about 50 pg/ml scopolamine and about 200 pg/ml biperiden.