Multiple drugs of abuse in urine detected with a single reagent and fluorescence polarization

We describe a simple polarization fluoroimmunoassay for the detection of several commonly abused drugs in urine. The single reagent used, prepared by mixing four different antisera and three fluorescein-labeled derivatives, produces a polarization signal that is the average of the individual signals of the derivatives. One adds urine to the pre-mixed reagent, incubates at room temperature for a few minutes, then measures fluorescence polarization. The presence of any of several abused drugs, at concentrations of 1 mg/L or more, noticeably decreases the average signal. Although other combinations are possible, the present assay detects the presence of a cocaine metabolite, amphetamine, and (or) several barbiturates.