PMID: 8721284Apr 1, 1996

Development of a fluorescence polarization immunoassay for lorazepam quantification

Therapeutic Drug Monitoring
P G AgbuyaA D Morris


Lorazepam concentrations have been quantified in biological fluids using gas chromatography and high-performance liquid chromatography (HPLC). However, these methods are too time consuming and labor intensive for most nonresearch laboratories to offer. A fluorescence polarization immunoassay (FPIA) method for quantification of lorazepam was developed and validated using a reverse-phase HPLC method as the reference method. The FPIA method involves a single liquid-liquid extraction of 100 microliters of either serum or plasma, then direct analysis using the TDxFLx (Abbott Diagnostics, North Chicago, IL). FPIA calibrations were linear between 50 and 800 ng/ml using five calibrators prepared in human serum. Within-run precision (n = 10) for three serum controls (75, 300, and 600 ng/ml) resulted in coefficients of variation (CVs) of 5.7%, 5.4%, and 4.2%, respectively. Between-day precision studies for the three serum controls were 7.0%, 8.9% and 4.9%, respectively (n = 5). The analytical recovery of the three serum controls was 104.9%, 97.3% and 98.3%, respectively. There was an excellent linear correlation between the FPIA and HPLC determinations of 43 patient specimens (r = 0.990, slope = 0.961, intercept = 16.3). No interferences...Continue Reading


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