Development of a liquid chromatography-tandem mass spectrometry method for determination of butoconazole nitrate in human plasma and its application to a pharmacokinetic study

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the determination of butoconazole in human plasma. Human plasma samples of 0.2 mu L were pretreated by a single step protein precipitation procedure and analyzed using a high performance liquid chromatography (HPLC) electrospray tandem mass spectrometer system. The compounds were eluted isocratically on an Inertsil ODS-SP column (100 mmx2.1 mm, 3 mu m), ionized using a positive ion atmospheric pressure electrospray ionization source and analyzed using multiple reaction monitoring (MRM) mode. The ion transitions monitored were m/z 412.8 -> 165.1 for butoconazole and m/z 453.4 -> 230.3 for the internal standard. The chromatographic run time was 3.5 min per injection, with retention time of 2.47 min and 2.15 min for butoconazole and repaglinide, respectively. The method was validated to be linear over the range of 20 to 8000 pg/mL (r > 0.999) by using a weighted (1/x(2)) quadratic regression. The mean recovery rate was more than 86.7%, and the intra- and inter-day precision of the quality control samples (QCs) was less than 8.3% and the accuracy ranged from 96.0% to 110.2%, which indicated that the quantitative method was reliable and accurate. The method is simple, rapid, and has been applied successfully to a pharmacokinetics study of butoconazole nitrate suppositories in healthy Chinese females.