Evaluation of an Ultrafiltration-Fluorescence Polarization Immunoassay for Monitoring Unbound Phenytoin

Publisher Website
Google Scholar
Abstract
To evaluate a new ultrafiltration-fluorescence polarization immunoassay (FPIA) for monitoring blood levels of unbound phenytoin, the drug, with or without a 14C label, was added to three serum pools obtained from normal, uremic, and hypoalbuminemic patients and to 10 individual patient sera that varied greatly in phenytoin binding (11–50%). Protein-unbound phenytoin fractions were obtained from the sera by ultrafiltration using the Amicon Micropartition System and by a classic equilibrium dialysis method. The percent unbound phenytoin in each serum was determined by a radioassay and an automated FPIA (TDx™ System). An analysis of variance revealed no significant difference in the percent unbound phenytoin obtained at 37°C by the FPIA and radioassay methods (α = 0.05). The data indicate that the ultrafiltration system can be combined with FPIA to produce a convenient lab-oratory method for routine therapeutic drug monitoring that gives results comparable to the equilibrium dialysis, radioassay reference method.

This publication has 2 references indexed in Scilit: