Effect of β-glucuronidase on urinary benzodiazepine concentrations determined by fluorescence polarization immunoassay

Abstract

In samples from patients treated with oxazepam, β-glucuronidase increased the immunoreactivity of urinary benzodiazepines analyzed by fluorescence polarization immunoassay (FPIA). Increasing concentrations of β- glucuronidase added to samples from drug-free controls did not influence the results. In the absence of β-glucuronidase, 22 of 35 samples from patients undergoing detoxification gave positive results at a cutoff concentration of 200 μg/L. Pretreatment with β-glucuronidase increased the number of drug- positive samples to 33. The drug-negative samples were obtained from two patients who had been oxazepam-free for at least 1 week. Thus, β- glucuronidase can be used to increase the sensitivity of the urinary benzodiazepine FPIA without reducing the specificity of the method.