Simultaneous determination of dexamethasone, dexamethasone 21-acetate, and paclitaxel in a simulated biological matrix by RP-HPLC: Assay development and validation

A simple and accurate reversed-phase high performance liquid chromatography method was developed and validated for the simultaneous determination of dexamethasone, dexamethasone 21-acetate, and paclitaxel in simulated biological matrix. Triamcinolone Acetonide was used as the internal standard (IS). A one step liquid-liquid extraction with ethyl acetate was used for sample cleanup. A gradient elution on a C-18 column with acetonitrile and 0.1% o-phosphoric acid in water was employed to get a cleanup baseline and efficient separation of the three chemical entities. Dexamethasone and dexamethasone 21-acetate were observed at 254 nm and paclitaxel was observed at 228 nm. The method was highly selective and the calibration curves were linear over the range of 0.25-10.0 mu g/mL with a 12 min chromatographic run time. The assay method was validated in terms of accuracy, precision, absolute recovery, freeze-thaw stability, bench top stability, and reinjection reproducibility. The lower limit of quantitation was 0.25 mu g/mL for all the analytes. The intra and inter-batch precision and accuracy were found to be well within acceptable limits (< 15%). The assay is simple, reliable, and fast and is deemed suitable for application to in vitro release rate studies of these drugs from implantable devices, as well as to their in vivo pharmacokinetic studies.