Determination of zolpidem in serum microsamples by high-performance liquidchromatography and its application to pharmacokinetics in rats

A single-solvent extraction step high-performance liquid chromatographic me thod is described for quantitating zolpidem in rat serum microsamples (50 m u l). The separation used a 2.1 mm I.D, reversed-phase OD-5-100 C-18 column , 5 mu m particle size with an isocratic mobile phase consisting of methano l-acetonitrile-26 mM sodium acetate buffer (adjusted to pH 2.0 with 40% pho sphoric acid) containing 0.26 mM tetrabutylammonium phosphate (13:10:77, v/ v/v). The detection limit was 3 ng/ml for zolpidem using an ultraviolet det ector operated at 240 nm. The recovery was greater than 87% with analysis p erformed in 12 min. The method is simple, rapid, and applicable to pharmaco kinetic studies of zolpidem after administering two intravenous bolus doses (1 and 4 mg/kg) in rats, (C) 1999 Elsevier Science B.V. All rights reserve d.