Development and validation of a rapid, sensitive liquid chromatography-tandem mass spectrometry method using electrospray ionization for quantitation of centchroman in rat plasma and its application to preclinical pharmacokinetic study.

A highly sensitive and specific HPLC-ESI-MS/MS method has been developed and validated for the estimation of centchroman with 100 microL rat plasma using tamoxifen as an internal standard (IS). The assay procedure involved a single-step, liquid-liquid extraction of centchroman and IS from plasma with 2.5% (v/v) isopropanol in n-hexane, which yielded consistent recoveries of 109.5 and 107.8% for centchroman and IS in rat plasma, respectively. The total chromatographic run time was 3.8 min. Peaks were resolved using 0.01 M ammonium acetate (pH 4.5):acetonitrile (10:90, v/v) mobile phase on a Supelco Discovery C(18) column. Specificity and matrix effect on ionization was determined and found that method was specific and there was no significant matrix effect. Linearity range was found to be 0.5-100.0 ng/mL with a correlation coefficient (r) of 0.9959 or better. The intra- and inter-day assay precision ranged from 3.3 to 9.0% and 5.5 to 6.8%, respectively, and intra- and inter-day assay accuracy was between 93.4-107.1% and 96.2-104.2%, respectively. Stability of centchroman in rat plasma was >89.0% in the battery of stability studies viz., bench-top, auto-sampler, freeze/thaw cycles and 30 days storage in a freezer at -80 degrees C. The assay was successfully applied to determine the pharmacokinetic parameters in Sprague-Dawley rats after an oral administration of centchroman at 20mg/kg. As a result, the plasma half-life was 29.4+/-2.3h and the AUC((0-infinity)) was 7345.1+/-21.9 ng h/mL. The maximum plasma concentration (C(max)) 117.5+/-15.7 ng/mL was achieved at 9.0+/-8.6h (t(max)).