Liquid Chromatography - Tandem Mass Spectrometry Method for Quantification of Zolpidem in Human Plasma: Application to Pharmacokinetic Study

A simple, rapid, and sensitive LC-MS/MS method for assay of Zolpidem in human plasma has been developed and validated using Zolpidem D6 as internal standard (IS). The extraction of analyte and IS was done using 100 mu L of plasma sample by solid phase extraction with Strata X (TM) 33 mu m polymeric sorbent cartridges. The processed plasma samples were separated using mixture of methanol and 5 mM ammonium acetate buffer in 0.1% formic acid (80:20, v/v) as mobile phase on a C18 column at a flow rate of 0.7 mL/min with total run time of 2.0 min. The quantification of the separated components was done in positive ion mode by Multiple Reaction Monitoring (MRM) with mass transitions from m/z 308.0 (parent ion) to m/z 235.0 (product ion) for Zolpidem and from m/z 314.2 (parent ion) to m/z 235.0 (product ion) for the IS. The method was linear in the concentration range of 2.0-200 ng/mL. The recovery was 82.49% and 84.24% for Zolpidem and IS. The inter- and intra-day accuracy and precision were in the range of 94.44 to 103.80% and 2.06 to 8.95%, respectively. The proposed method was successfully applied for pharmacokinetic study of Zolpidem in human volunteers after single oral dose of 10 mg under fasting conditions and incurred sample reanalysis was also performed.