Determination of DP-VPA and its active metabolite, VPA, in human plasma, urine, and feces by UPLC-MS/MS: A clinical pharmacokinetics and excretion study

DP-VPA is a phospholipid prodrug of valproic acid (VPA) that is developed as a potential treatment for epilepsy. To characterize the pharmacokinetics and excretion of DP-VPA, four reliable ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) methods were validated for quantitation of DP-VPA and its metabolite, VPA, in human plasma, urine, and feces. Protein precipitation and solid-phase extraction (SPE) were used for extraction of C16, C18 homologs of DP-VPA and VPA, respectively, from plasma. Urine and fecal homogenate involving the three analytes were efficiently prepared by methanol precipitation. The determinations of C16 DP-VPA, C18 DP-VPA, and VPA were performed using the positive multiple reaction monitoring (MRM) mode and the negative single ion monitoring (SIM) mode, respectively. The analytes were separated using gradient elution on C8 or phenyl column. Satisfactory results pertaining to selectivity, linearity, matrix effect, accuracy and precision, recovery, stability, dilution integrity, carryover, and incurred sample analysis (ISR) were obtained. The calibration ranges in human plasma were as follows: 0.00200-1.00 mu g/mL for C16 DP-VPA, 0.0100-5.00 mu g/mL for C18 DP-VPA, and 0.0500-20.0 mu g/mL for VPA. The linear ranges in urine and fecal homogenate were 0.00500-2.00 mu g/mL and 0.00200-0.800 mu g/mL for C16 DP-VPA, 0.00500-2.00 mu g/mL and 0.0100-4.00 mu g/mL for C18 DP-VPA, and 0.200-80.0 mu g/mL for VPA, respectively. The intra- and inter-batch coefficients of variation in three matrices ranged from 1.7% to 12.4% while the accuracy values ranged from 85.4% to 111.7%. The developed methods were successfully applied to determine pharmacokinetics of DP-VPA tablet after a single oral dose of 1200 mg in 12 healthy Chinese subjects under fed condition.