15 A HPLC-UV/VIS method for the quantification of valproic acid in human serum

Introduction Valproic acid (VPA) nowadays is not only used for the treatment of epilepsies, but also for schizophrenia, bipolar disorder, and several off-label indications. Except for epilepsies, therapeutic reference ranges (TRR) for useful therapeutic drug monitoring (TDM) are scarce. Most TDM-methods rely on HPLC-MS or immunological methods, because HPLC-analysis via UV/VIS-detection of VPA is challenging. However, occurring VPA concentrations showed to be high enough for reliable UV/VIS-detection. Developing a HPLC-UV/VIS method for the quantificantion of VPA in serum samples would give more laboratories the possibility to offer TDM.

Methods A simple and rapid method for the quantification of VPA in serum samples via HPLC-UV/VIS was developed. Sample preparation consisted of a protein precipitation step followed by centrifugation. Elution was performed under isocratic conditions with a mixture of methanol and phosphate buffer at pH 2.4. Detection wavelength was 210 nm and the total runtime 8 minutes.

Results The method was validated according to the FDA guideline for bioanalytical method validation and showed linearity over a concentration range from 5–300 µg/ml, with a limit of detection of 3 µg/ml. The recovery rate was found to be 96.97 %. 269 drugs and metabolites were tested and showed no interference with the analyte.

Conclusion This novel method will enable the determination of VPA-concentration in human serum in order to assess TRRs suitable for other indications than epilepsy. As the method provides a broad calibration range, measuring samples even far outside the epileptic TRR is ensured. Therefore, it is suitable for routine TDM and a valuable tool for making VPA treatment simpler and safer.

Publication History

Article published online:
30 April 2020