A simple, precise, and sensitive HPLC method for quantification of letrozole in rat plasma: development, validation, and preclinical pharmacokinetics

A simple bioanalytical liquid chromatographic method was developed and validated to quantify letrozole (LTZ) in rat plasma. Protein precipitation using acidified chilled acetonitrile (containing 0.1% orthophosphoric acid) was used to extract LTZ from the plasma. Chromatographic separation was carried out on Kinetex C18 reverse phase (RP) column (250 mm × 4.6 mm i.d., 5 μm) using a mixture of 20 mM acetate buffer (pH 5.5) and acetonitirile (60:40 %v/v) eluting at 1.0 mL/min flow rate with the method responses measured at 240 nm. The optimized method was selective and established good linearity with recovery ranging between 91.16 and 99.44%. The validation experiments revealed that the method showed acceptable precision (2.61–7.48%) and accuracy (97.44–102.70%) and was found to be stable. The sensitivity of the method was demonstrated by the lowest concentration (LLOQ) detected at 75 ng/mL. Using the developed method, single-dose oral pharmacokinetics in Sprague-Dawley rats was carried out to successfully confirm the applicability of the method for the quantification of LTZ in biological matrix.