LC-MS/MS method for quantification and pharmacokinetic study of gabapentin in human plasma

A sensitive, rapid and specific liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method for quantification of gabapentin in human plasma has been developed.  After a single plasma protein precipitation with methanol, gabapentin and metformin (internal standard) were chromatographed on a Inertsil ODS-3 column (50 mm × 2.1 mm ID, 3 μm) with mobile phase consisting of methanol−0.2% formic acid aqueous solution (80∶20, v/v) at a flow-rate of 0.2 mL·min⁻¹.  Electrospray ionization (ESI) source was applied and operated in the positive ion mode.  Multiple reaction monitoring (MRM) mode with the transitions of m/z 172 → m/z 154 and m/z 130 → m/z 71 were used to quantify gabapentin and metformin, respectively.  The run time was 2.2 min.  The linear calibration curve was obtained in the concentration range of 40.8−8.16×10³ ng·mL⁻¹.  The lower limit of quantification was 40.8 ng·mL⁻¹.  The intra- and inter-day precision (RSD) was less than 12%, and the accuracy (RE) was within ±6.4% calculated from quality control (QC) samples.  The method was used to determine the concentration of gabapentin in human plasma after a single oral administration of 600 mg gabapentin capsule to 20 healthy male Chinese volunteers.  The method was proved to be selective, sensitive, rapid and suitable for pharmacokinetic study of gabapentin in human plasma.