803ESTIMATION OF SILDENAFIL USING DERIVATIVE SPECTROPHOTOMETRY IN BULK MATERIAL AND IN PHARMACEUTICAL FORMULATIONFour simple, rapid, accurate, precise, reliable, and economical UV-spectrophotometric methods have been proposed for the determination of Sildenafil in bulk and in pharmaceutical formulation. “Method A” is first order derivative UV spectrophotometry using amplitude, “method B” is first order derivative UV spectrophotometry using area under curve technique, “method C” is second order derivative UV spectrophotometry using amplitude, and “method D” is second order derivative UV spectrophotometry using area under curve technique. The developed methods have shown best results in terms of linearity, accuracy, precision, and LOD and LOQ for bulk drug and marketed formulation as well. In N, N-dimethyl formamide (DMF), Sildenafil showed maximum absorbance at 292 nm. For “method A” amplitude was recorded at 313 nm while for “method B” area under curve was integrated in the wavelength range of 302-326 nm. For “method C” amplitude was measured at 297 nm while for “method D” area under curve was selected in the wavelength range of 281-310 nm. For methods A, B, C and D, Sildenafil obeyed Lambert-Beer’s law in the range of 05–50 µg/mL, and the correlation coefficients were found to be > than 0.999. The methods were validated and found to be simple, sensitive, accurate, and precise. Hence, the methods can be used successfully for routine analysis of pharmaceutical dosage form of Sildenafil.drx.mudassar@gmail.comResearch922018Sildenafil, UV Spectroscopy, Derivatives Methods, Area Under Curve.Rajveer Bhaskar,Monika Ola,Mohammad MudassarRajveer Bhaskar,Monika Ola,Mohammad Mudassar