An Improved LC-ESI-MS/MS Method to Quantify Pregabalin in Human Plasma and Dry Plasma Spot for Therapeutic Monitoring and Pharmacokinetic Applications

Abstract

Background: Therapeutic drug monitoring (TDM) of antiepileptic drugs provides a valid clinical tool in optimization of overall therapy. However, TDM is challenging because of the high biological sample (plasma/blood) storage/shipment costs and the limited availability of laboratories providing TDM services. Sampling in the form of dry plasma spot (DPS) or dry blood spot is a suitable alternative to overcome these issues.

Methods: An improved, simple, rapid, and stability-indicating method for quantification of pregabalin (PGB) in human plasma and DPS has been developed and validated. Analyses were performed on liquid chromatography-tandem mass spectrometer under positive ionization mode of electrospray interface. PGB-d4 was used as internal standard, and the chromatographic separations were performed on Poroshell 120 EC-C18 column using an isocratic mobile phase flow rate of 1 mL/min. Stability of PGB in DPS was evaluated under simulated real-time conditions. Extraction procedures from plasma and DPS samples were compared using statistical tests. The method was validated considering the Food and Drug Administration method validation guideline.

Results: The method was linear over the concentration range of 20-16,000 ng/mL and 100-10,000 ng/mL in plasma and DPS, respectively. DPS samples were found stable for only 1 week on storage at room temperature and for at least 4 weeks at freezing temperature (-20 ± 5°C). Method was applied for quantification of PGB in over 600 samples of a clinical study. Statistical analyses revealed that 2 extraction procedures in plasma and DPS samples showed statistically insignificant difference and can be used interchangeably without any bias.

Conclusions: Proposed method involves simple and rapid steps of sample processing that do not require a precolumn or postcolumn derivatization procedure. The method is suitable for routine pharmacokinetic analysis and therapeutic monitoring of PGB.