Simultaneous Spectrophotometric Estimation of Lornoxicam and Thiocolchicoside in Combined Dosage Form

Two simple, rapid, accurate and economic spectrophotometric methods are described for the determination of Lornoxicam (LOR) and Thiocolchicoside (THIO) in combined dosage form. The first method is Ratio Spectra Derivative and second is Absorption Corrected method. Methanol was used as solvent for both the methods. First method was measurement of amplitude of first order derivative of ratio spectra where LOR and THIO were determined at λ_max 445.21 nm and 371.79 nm, respectively. The second method was based on the absorption corrected method in which LOR and THIO exhibit λ_max at 435 nm and 333.74 nm, respectively in methanol. LOR has some interference due to THIO at 333.74 nm, while THIO do not show any absorption at 435 nm. Quantitative estimation of THIO was carried out by subtracting the absorption due to LOR at 333.74 nm using experimentally calculated absorption factor. Both the drugs obey Beer's law in the concentration ranges employed for these methods. The results of analysis have been validated statistically and recovery studies confirmed the accuracy and reproducibility of the proposed methods which were carried out by following ICH guidelines.