A rapid, robust, simple, selective, and sensitive liquid chromatography‐tandem mass spectrometry method was developed for the simultaneous estimation of obeticholic acid and its two pharmacologically active metabolites, glyco‐obeticholic acid, and tauro‐obeticholic acid in human plasma. The analytes and their heavy stable isotope‐labeled internal standards were extracted from 250 μL human plasma by a solid‐phase extraction technique. The method linearity was established over a concentration range of 0.410 to 120.466 ng/mL for obeticholic acid, 0.414 to 121.708 ng/mL for glyco‐obeticholic acid, and 0.255 to 75.101 ng/mL for tauro‐obeticholic acid. The method was fully validated as per current guidelines on bioanalytical method validation of “United States of Food and Drug Administration” and “European Medicines Agency.” The method was successfully applied to study the pharmacokinetics of obeticholic acid, glyco‐obeticholic acid, and tauro‐obeticholic acid following oral administration of obeticholic acid tablets to healthy male volunteers. All the measured concentrations were within calibration curve ranges.

A simple, specific, selective and accurate bioanalytical method was developed and validated for simultaneous estimation of acalabrutinib and its active metabolite in human plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

A highly sensitive liquid chromatography–tandem mass spectrometry method was developed to estimate azathioprine in presence of its active metabolite mercaptopurine in human plasma. The analyte and isotope‐labeled internal standards were extracted from 300 μL human plasma by a solid‐phase extraction technique. The method was revealed good linearity over a concentration range of 0.151 to 49.500 ng/mL for azathioprine, containing 50.000 ng/mL of mercaptopurine in all the quality control samples. The detection was established using multiple reaction monitoring method. The method validation was carried out as per the present guidelines on bioanalytical method validation of European medicines agency and United States Food and Drug Administration. The current method was successfully applied to study the pharmacokinetics of azathioprine 50 mg tablets on healthy human volunteers. The results of pharmacokinetic parameters have demonstrated that, estimation of azathioprine in presence of mercaptopurine has no impact on azathioprine results.