CEDIA dau Benzodiazepine screening assay: a reformulation

The CEDIA dau Benzodiazepine assay has been reformulated to include online hydrolysis of urinary benzodiazepine glucuronide conjugates. The new antibody possesses enhanced cross-reactivities toward the low-dose benzodiazepines, which are excreted at low urinary drug-metabolite concentrations. The screening method was evaluated using lorazepam as the probe benzodiazepine. Four subjects each consumed a 1-mg lorazepam tablet. Sequential urine voids over the same time intervals were collected for the next 48 h. Twelve postdose urine samples were collected from each subject. Positive results were obtained from 5-24 h to 2-35 h using a 200-ng/mL nitrazepam calibration cutoff. There was no practical difference between hydrolyzing online with the supplied E. coli beta-glucuronidase or offline with Helix pomatia beta-glucuronidase purchased separately. Without hydrolysis, all urine samples tested negative. The cross-reactivities of lorazepam in terms of nitrazepam calibration equivalents, varied from 108 to 178% for lorazepam concentrations between 50 and 2500 ng/mL. Lorazepam glucuronide gave cross-reactivities (expressed as lorazepam base) between 72 and 136% using the online hydrolysis procedure with E. coli beta-glucuronidase. Offline hydrolysis with Helix pomatia gave cross-reactivities between 84 and 134%. Without hydrolysis, lorazepam glucuronide gave less than 4% cross-reactivity in the assay.