Bioanalysis and Validation of Fesoterodine, an Antimuscarinic Agent and its Active Metabolite Using Liquid Chromatography with Tandem Mass Spectrometry

Aim: To establish a bioanalytical method with rapid, specific and sensitiveness with tandem mass spectrometric with liquid chromatography for an antimuscuranic agent, fesoterodine and its metabolite, 5-hydroxy methyl tolterodine in plasma of human, using their isotopic labeled compounds correspondingly, with internal standards, fesoterodine d14 and 5-hydroxy methyl tolterodine d14. Materials and Methods: The extraction of analytes is by employing tert-butyl methyl ether, divided with Kromasil 100 column C18 using the mixture of mobile phase containing methanol and 5 mM ammonium formate buffer (PH 3.5) at a rate of 1 mL/min. The outstanding linearity was shown in the range of concentrations, 0.1022 to 15.0154 and 0.1022 to 15.0211 ng/ mL for fesoterodine and its metabolite simultaneously. The lower limit of quantitation values is 0.1022 and 0.1022 ng/mL respectively for fesoterodine and 5-hydroxy methyl tolterodine. Results: The accuracy and repeatability results for four different batches at five different concentration levels were discovered to be in the limits of acceptability for ICH guidelines. Stability tests, including benchtop, injector, freeze-thaw cycles, and -20ºC storage, confirmed fesoterodine and its metabolite stability in plasma. The chromatographic elution time of 2.5 min enabled the analysis of 300 samples rapidly in a day for the established technique. Validation results qualified the method for regular analysis and pharmacokinetic studies of fesoterodine and 5-hydroxy methyl tolterodine, its metabolite in the human biological fluid, plasma.