A simple, selective and rapid validated method for estimation of anastrazole in human plasma by liquid chromatography-tandem mass spectrometry and its application to bioequivalence study.

A rapid, simple and specific method for estimation of anastrazole in human plasma was validated using letrozole as internal standard. The analyte and internal standard were extracted from plasma using simple solid-phase extraction. The compound were separated on a reverse-phase column with an isocratic mobile phase consisting of 0.1% formic acid in water and acetonitrile (12 : 88, v/v) and detected by tandem mass spectrometry in positive ion mode. The ion transitions recorded in multiple reaction monitoring mode were m/z 294.1 --> 225.1 for anastrazole and m/z 286.1 --> 217.1 for internal standard. Linearity in plasma was observed over the concentration range 0.3-30 ng/mL for anastrazole. The mean recovery for anastrazole was 83.7% with a lower limit of quantification of 0.3 ng/mL. The coefficient of variation of the assay was less than 6.8% and the accuracy was 96.1-102.2%. The validated method was applied to a bioequivalence study of 1 mg anastrazole tablet in healthy human volunteers.