[Fluorescence polarization immunoassay of isepamicin in blood spotted on filter paper]

A simple method has been developed for the determination of the aminoglycoside antibiotic isepamicin (ISP) in whole blood, using dried blood spots (DBSs) on filter-paper. ISP in the DBSs were recovered most effectively in 0.5 M Na2HPO4-NaH2PO4 buffer (pH 7) by incubation for 30 minutes at 35 degrees C in an ultrafiltration tube. The eluates from the DBS papers were centrifuged at 3,000 x g for 10 minutes. The clear, colorless filtrates were transferred to an Abbott TDx cartridge for measurement by the fluorescence polarization immunoassay. The lower limit for the quantitative determination of ISP in the DBS was 2.5 micrograms per ml of whole blood. The method permits a simple collection of blood at a microliter level and should prove particularly useful for therapeutic drug monitoring of ISP in blood at effective levels in pediatric and geriatric patients.