Treatment protocols combining tamsulosin and solifenacin proved better management of the complicated urinary tract symptoms. The pharmaceutical preparations of tamsulosin and solifenacin suffered from the high difference in their ratio, 0.4 mg tamsulosin and 6 mg solifenacin, and strong spectral overlap. Here, we developed four simple, accurate and selective spectrophotometric methods based on simple mathematical manipulations. These methods require the simplest mathematical filtration using short steps performed using built-in functions of the spectrophotometer operating software utilizing zero-order or derivative spectra. These methods are namely absorption correction method (ACM), induced dual-wavelength (IDW), absorptivity factor method (AFM) and first derivative method (D1). The linear ranges were 15-70 µg/ml and 100-1200 µg/ml for TAM and SFN, respectively. The limits of quantitation were in the range of 3.8-4.05 µg/ml and 23.34-59.05 µg/ml, while the limits of detection were in the range of 1.25-1.34 µg/ml and 7.7-24.6 µg/ml for TAM and SFN, respectively. All validation parameters investigated as per ICH guidelines. A statistical comparison executed for the proposed methods with each other and with the reported methods showed no significant difference between the proposed and the reported methods.
Keywords: Absorption correction method (ACM); Absorptivity factor method (AFM); First derivative method (D(1)); Induced dual-wavelength (IDW); Solifenacin; Tamsulosin.
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