Validated Spectrophotometric Methods for Simultaneous Determination of Atorvastatin Calcium and Olmesartan Medoxomil in Their Pharmaceutical Formulation

Background Few spectrophotometric methods have been developed for the simultaneous determination of atorvastatin calcium (ATO) and olmesartan medoxomil (OLM). Objective This work aimed to develop and validate five simple spectrophotometric methods for the simultaneous estimation of ATO and OLM in their tablet form. Methods Method I applied the area under curve (AUC) based on the measurement of areas between 241 and 261 nm for ATO, and 248 and 263 nm for OLM. Method II applied second derivative spectrophotometry where the analytical amplitudes at 246.5 and 235 nm were chosen for the estimation of ATO and OLM, respectively. Method III applied the ratio difference (RD) method based on the measurement of amplitude difference (Delta P) within ratio spectra; Delta P ((240-260 nm)) was directly related to ATO concentration, and Delta P ((262-240 nm)) was directly related to OLM concentration. Method IV depended on the absorbance ratio method in which the wavelength at the iso-absorptive point (lambda(ISP)) and the maximum absorbance wavelength (lambda(max)), 277 and 255.5 nm, respectively, were used to calculate OLM concentration, while ATO concentration was determined from the zero-order UV spectra at 300 nm. Method V utilized a dual wavelength (DW) technique where Delta A between 247.5 and 262 nm was directly related to ATO concentration, and Delta A between 216 and 238 nm was directly related to OLM concentration. Results The results of the assays indicated good mean % recovery +/- SD as well as good agreement with the reported method. Conclusion Five simple and rapid spectrophotometric methods were developed, validated, and successfully applied for simultaneous estimation of ATO and OLM tablets.