Specific stability indicating spectrofluorimetric method for determination of ledipasvir in the presence of its confirmed degradation products; application in human plasma

A rapid and specific spectrofluorimetric method with higher sensitivity was developed for determination of ledipasvir (LDS) in tablets and human plasma. The proposed method relies on hydrogen bonding formations between the hydroxyl groups of polyoxyethylene 50 stearate and LDS, causing significant enhancement of its native fluorescence. The fluorescence intensity was measured at 430 nm after excitation at 340 nm. The fluorescence-concentration plot was rectilinear over the range 1-400 ng mL^-1 with detection and quantification limits of 0.25 and 1.10 ng mL^-1, respectively. The high sensitivity of the proposed method permits its application for ledipasvir determinations in real human plasma even in the presence of co-administered drugs sofosbuvir and ribavirin. Moreover, the proposed method was further extended to stability studies of ledipasvir after exposure to different forced degradation conditions according to ICH guidelines, along with the structural elucidation of its degradation products utilizing IR and Mass spectra. A proposal for the degradation pathways was presented.