STABILITY-INDICATING RP-HPLC METHOD FOR THE SIMULTANEOUS DETERMINATION OF AMLODIPINE BESYLATE AND AZILSARTAN MEDOXOMIL IN TABLET DOSAGE FORM

A novel, simple, rapid, and highly selective stability indicating RP-HPLC method was developed and validated for simultaneous estimation of azilsartan medoxomil (AZL) and amlodipine besylate HCl (AMLO) in tablet dosage form having strength of 20 mg and 2.5 mg, respectively. The effective chromatographic separation was achieved on a Phenomenex luna ODS C18 (15 cm X 4.6 mm internal diameter, 3.5 μm Particle size) with a mobile phase composed of phosphate buffer (pH-2.5) adjusted with ortho phosphoric acid : acetonitrile in the ratio of 60:40 v/v. The mobile phase was pumped using an isocratic HPLC system at a flow rate of 0.7 mL/min with injection volume 20μl and quantification of the analytes was done at detection wavelength 254 nm. The retention times were found to be 5.918 min and 14.901 min for AMLO and AZL, respectively. The proposed HPLC method was validated with respect to linearity, ranges, precision, accuracy, specificity, robustness, LOD, and LOQ as per ICH Q2 (R1) guideline. Calibration plots were linear over the concentration range of 75-125 µg/mL and 600-1000 µg/mL with correlation coefficients 0.9966 and 0.9948 for AMLO and AZL, respectively. Forced degradation studies were performed using hydrolysis, oxidation, photolytic, and thermal degradation conditions with good resolution between the degradants and analytes. Degradation products resulting from the stress studies did not interfere with the detection of AMLO and AZL, thus the proposed method is sensitive and stability-indicating. The validated HPLC method was successfully applied to the analysis of AMLO and AZL in tablet dosage form.