title: Liquid chromatography-mass spectrometry method for the quantification of tamoxifen and its metabolite 4-hydroxytamoxifen in rat plasma: application to interaction study with biochanin A (an isoflavone).
abstract: Tamoxifen is the agent of choice for the treatment of estrogen receptor-positive breast cancer. Tamoxifen is a substrate of P-glycoprotein (P-gp) and microsomal cytochrome P450 (CYP) 3A, and biochanin A (BCA) is an inhibitor of P-gp and CYP3A. Hence, it could be expected that BCA would affect the pharmacokinetics of tamoxifen. In the present study we have developed and validated a simple, sensitive and specific LC-ESI-MS/MS method for the simultaneous quantification of tamoxifen and its metabolite 4-hydroxytamoxifen with 100 μL rat plasma using centchroman as an internal standard (IS). Tamoxifen, 4-hydroxytamoxifen and IS were separated on a Supelco Discovery C18 (4.6 mm × 50 mm, 5.0 μm) column under isocratic condition using 0.0 1M ammonium acetate (pH 4.5):acetonitrile (10:90, v/v) as a mobile phase. The mobile phase was delivered at a flow rate of 0.8 mL/min. The method was proved to be accurate and precise at linearity range of 0.78-200 ng/mL with a correlation coefficient (r) of ≥ 0.996. The intra- and inter-day assay precision ranged from 1.89 to 8.54% and 3.97 to 10.26%, respectively; and intra- and inter-day assay accuracy was between 87.63 and 109.06% and 96 and 103.89%, respectively for both the analytes. The method was successfully applied to study the effect of oral co-administration of BCA (an isoflavone) on the pharmacokinetics of tamoxifen and 4-hydroxytamoxifen in female rats. The coadministration of BCA caused no significant changes in the pharmacokinetics of tamoxifen and 4-hydroxytamoxifen. However, the peak plasma concentration (C(max)) of 4-hydroxytamoxifen in BCA pretreated rats was significantly (P<0.05) lower than those from control group.
authors: Pharmacokinetics and Metabolism Division, Central Drug Research Institute, CSIR (Council of Scientific and Industrial Research), Lucknow 226001, Uttar Pradesh, India.
authors: Sheelendra Pratap
authors: SP
authors: Singh
authors: Wahajuddin
authors: Mushir M
authors: MM
authors: Ali
authors: Kanchan
authors: K
authors: Kohli
authors: Girish Kumar
authors: GK
authors: Jain
mesh_terms: D000818:Animals; D019540:Area Under Curve; D002486:Centchroman; D002853:Chromatography, Liquid / Q000379:methods*; D004347:Drug Interactions; D005260:Female; D019833:Genistein / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013629:Tamoxifen / Q000031:analogs & derivatives* / Q000097:blood* / Q000493:pharmacokinetics / Q000494:pharmacology; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D013629:Tamoxifen; C016601:afimoxifene; D002486:Centchroman; D019833:Genistein; C004541:biochanin A