A Sensitive Ultrafiltration Plus RP-HPLC-FLD Method to Quantify Total and Free Perampanel Concentrations in the Plasma of Patients With Epilepsy: A Fully Validated Assay With Clinical Application.

Background: Perampanel (PER), a novel antiepileptic drug, exhibits high protein binding. Given the drug's susceptibility to various factors, including drug interactions, and the considerable variability in blood concentrations among individuals, solely measuring the total plasma concentration of PER may not provide comprehensive insights. This study aimed to establish an HPLC-FLD method to quantify both total and free PER in clinical samples.

Methods: Analysis of total PER involved a straightforward sample preparation process involving plasma protein precipitation. Plasma samples were ultrafiltered to isolate the free portion of PER. Chromatographic separation was achieved on an InertSustain C18 column at a 1-mL/min flow rate using a gradient of acetonitrile and aqueous sodium acetate buffer at pH 4.4.

Results: Calibration curves for total and free PER in plasma exhibited excellent linearity over the concentration ranges of 10-3000 and 0.5-100 ng/mL, respectively. The method was applied to analyze blood samples from patients with epilepsy quantitatively; the total concentration of perampanel in the plasma of the patients was in the range of 90.45-563.39 ng/mL, whereas the free concentration was in the range of 1.82-15.29 ng/mL. The plasma protein binding ratio of perampanel was normally between 97.09% and 99.29% and decreased in cases of hypoproteinemia.

Conclusions: The method was rigorously validated for selectivity, accuracy, precision, and stability in accordance with established FDA and EMA guidelines. The developed method enables the rapid and accurate quantification of both total and free PER concentrations in the plasma of patients with epilepsy, offering technical support for its subsequent clinical application.