Validated Chromatographic and Spectrofluorimetric Methods for Analysis of Silodosin: A Comparative Study with Application of RP-HPLC in the Kinetic Investigation of Silodosin Degradation

BACKGROUND Stability indicating determination of pharmaceuticals is crucial, especially for drugs which have few published official analytical methods. Silodosin (SLD) is an FDA approved α1A-adrenoceptor blocker. OBJECTIVE Efficient analytical methods were suggested, based on different instrumental techniques for quantification of SLD, besides conducting kinetic investigation of its degradation. METHODS The first method is based on Reversed Phase High Performance Liquid Chromatography with Photodiode Array Detector (RP-HPLC-PDAD). Detection is done at wavelength 225 nm. The second method is focused on using High Performance Thin Layer Chromatography (HPTLC) and eluting the drug by solvent mixture followed by scanning at wavelength 270 nm. The third method depends on the First Derivative Synchronous Fluorescence Spectroscopy (1DSFS) for analysis of solutions of SLD and its acid and oxidative induced degradation products at Δλ = 90 nm, then determining the first derivative of the spectra and measuring peak amplitudes at 360 nm. RESULTS Acceptable linearities were found in the concentration range of 0.50-90 μg/mL, 0.10-3.0 μg/band, and 0.05-0.50 µg/mL, for RP-HPLC-PDAD, HPTLC, and spectrofluorimetric methods, respectively. CONCLUSION Statistical analysis showed no significant difference between the suggested and the reported method. In monitoring the kinetics of SLD degradation, the order of reactions was determined and effects of degrading agent concentration and temperature on reaction rate were studied. HIGHLIGHTS Three analytical methods were developed for the determination of SLD based on RP-HPLC-PDAD, HPTLC, and 1DSFS in bulk and capsule dosage form. In addition, kinetic investigation of SLD degradation was performed using the developed RP-HPLC-PDAD method.