Highly sensitive and rapid LC-ESI-MS/MS method for the simultaneous quantification of uroselective alpha1-blocker, alfuzosin and an antimuscarinic agent, solifenacin in human plasma.

An accurate, selective and sensitive bioanalytical method has been developed and validated for the simultaneous quantification of alfuzosin and solifenacin in human plasma using propranolol as internal standard (IS). The analytes and IS were extracted in methyl tert-butyl ether, separated on Hypurity C8 column and detected by tandem mass spectrometry with a turbo ion spray interface. The method had a chromatographic run time of 3.0 min and linear calibration curves over the concentration range of 0.25-25 ng/mL for alfuzosin and 0.6-60 ng/mL for solifenacin. The intra- and inter-day accuracy and precision (%CV) evaluated at four quality control levels were within 88.2-106.4% and 0.9-7.7% respectively. The absolute recovery from spiked plasma samples was 71.8% for alfuzosin and 93.1% for solifenacin. Stability of alfuzosin and solifenacin was assessed under different storage conditions. The validated method was successfully employed for bioavailability study after oral administration of 10 mg of alfuzosin hydrochloride and 5mg of solifenacin succinate tablet formulations in eight healthy volunteers under fed condition.