Simple radioligand binding assay for the determination of urinary scopolamine

A sensitive radioligand binding assay is described for the determination of scopolamine in human urine. As a measure for the drug concentration, the quantitative displacement of scopolamine of tritiated quinuclidinyl benzylate from rat brain receptors was used. The assay is sensitive to concentrations as low as 1.2 ng/mL, surpassed only by GC-MS techniques. It can be performed easily and quickly and does not include extraction procedures. Scopoline and scopine , possible metabolites of scopolamine, do not interfere with the assay. After transdermal administration of scopolamine, 34% of the drug is found in the urine. Of the total scopolamine excreted, 79% is conjugated to glucuronic and/or sulfuric acid and 21% is excreted in the unbound form.