Quantification of estradiol cypionate in plasma by liquid chromatography coupled with tandem mass spectrometry: Application in a pharmacokinetic study in healthy female volunteers

The combination of medroxyprogesterone acetate 25 mg + estradiol cypionate 5 mg is a highly effective, monthly injectable contraceptive. For the first time, this study presents the development and validation of a sensitive method for estradiol cypionate analysis in human plasma by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Aliquots (500 mu L) of plasma were extracted with ethyl ether (100%) and derivatized with dansyl chloride. Its separation was performed on a Jones Chromatography Genesis C8 column and the quantification was performed with a mass spectrometer equipped with an electrospray interface operating in negative ion mode. The run time was 6 min and the calibration curve was linear over the range of 0.005-0.15 ng/mL. The method was applied to evaluate the pharmacokinetics of estradiol cypionate in plasma collected up to 1008 h (42 days) after a single intramuscular administration of 25 mg/mL medroxyprogesterone acetate +5 mg/mL estradiol cypionate to healthy female volunteers (n =12). The estradiol cypionate maximum plasma concentration (C-max) was 0.14 +/- 0.08 ng/mL reached at 16.83 +/- 21.07 h and the area under the plasma concentration versus time curve (AUC(0-last)) was 14.07 +/- 6.32 ng.h/mL. Elimination half-life (t(1/2)), apparent volume of distribution (Vd/F), apparent clearance (CL/F) and mean residence time (MRT) were 89.65 +/- 76.04 h, 28038 +/- 9636 L, 49.02 +/- 10.62 L/h and 576.05 +/- 238.32 h, respectively, showing that the estradiol cypionate release from the administration site was prolonged and there was no drug accumulation. (C) 2019 Elsevier B.V. All rights reserved.