Simultaneous determination of oxiracetam and its degraded substance in rat plasma by HPLC-MS/MS and its application to pharmacokinetic study after a single high-dose intravenous administration

A simple, rapid and sensitive reversed-phase ultra-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method was developed and validated for the simultaneous quantitative determination of oxiracetam and its degraded substance 4-hydroxy-2-oxo-1-pyrrolidine acetic acid (HOPAA) in rat plasma. After plasma samples were deproteinized with acetonitrile, the post-treatment samples were analyzed on a C18 column interfaced with a triple quadrupole tandem mass spectrometer in the positive electrospray ionization mode at a flow rate of 0.35 ml/min. Piracetam was used as internal standard (IS). Multiple selected reaction monitoring was performed using the transitions m/z 159.00 → 141.94, 159.95 → 113.98 and 142.98 → 125.97 to quantify oxiracetam, HOPAA and IS, respectively. This method was validated over the concentration range of 25–2250 μg/ml for oxiracetam (r2 ≥ 0.99) and 0.5–250 μg/ml (r2 ≥ 0.99) for HOPAA. Intra-run and inter-run precision values of oxiracetam and HOPAA were less than 15% and accuracy was within 85–115% at all quality control levels. The average extraction recovery was 93.9% for oxiracetam and 95.6% for HOPAA, respectively. In conclusion, a simple, sensitive and specific HPLC-MS/MS method was successfully applied to the pharmacokinetic study in rats after an intravenous administration at a high dose of 2 g/kg.