Design of experiments-based RP - HPLC bioanalytical method development for estimation of Rufinamide in rat plasma and brain and its application in pharmacokinetic study.

This study reports a fully validated HPLC-UV (High Performance Liquid Chromatography- Ultra Violet) method for quantitative estimation of Rufinamide (RUFI), an antiepileptic drug, in rat plasma and brain matrices. A response surface methodology based Box Behnken experimental design, using the principles of Design of Experiments (DoE), was employed to optimize critical chromatographic conditions viz. pH and proportion of the buffer and wavelength of detection, for achieving good sensitivity (peak area) and specificity (number of theoretical plates). A desirability function was employed to identify the optimized conditions, which gave a highest value of 0.971. The optimized chromatographic conditions were: pH of the buffer: 4.7, wavelength of detection: 215 nm and proportion of buffer in mobile phase: 84.7% v/v for responses: 124839.6 mV ∗ min as the peak area (1 μg/mL) and 20,000 as the theoretical plate number for the same. A simple protein precipitation method, using methanol, was employed to extract RUFI from the biological matrices. Piribedil was used as the internal standard (IS). At the optimized conditions, the LOQ values of RUFI in plasma and brain were found to be 13.84 ng/mL and 105.24 ng/g respectively. The developed method was validated as per ICH guidelines and its applicability in analysing RUFI in rat plasma and brain matrices was demonstrated by i.v. administration in rats. The AUC0-t in plasma was found to be 91.9% of AUC0-∞ indicating that the method is very sensitive and can capture almost the entire plasma time course of RUFI, at a dose of 0.5 mg/kg.