Acid-alkali degradation study on olmesartan medoxomil and development of validated stability-indicating chromatographic methods

Abstract

A reversed phase liquid chromatography (RP-HPLC) and thin layer chromatography (HPTLC) densitometry methods as a stability indicating assays of olmesartan medoxomil in presence of its acid or alkaline induced degradation products were developed. Olmesartan medoxomil and its degradation products were analyzed by HPLC equipped with UV-Variable wave length detector at 257 nm where quantitation was achieved by isocratic elution on Agilent, Exclipse XDB-C 18 column with mobile phase composed of acetonitrile: methanol: water: glacial acetic acid (40:35:25:0.1 v/v/v/v) at flow rate 1ml min. -1. HPTLC was performed on aluminum packed Nano silica gel 60 F 254 TLC plates as stationary phase with significant difference in Rf values between olmesartan medoxomil and its degradates using chloroform: methanol: formic acid (8:1.5:0.5 v/v/v) as mobile phase. Densitometric evaluation of intact drug was carried out at 260 nm. The calibration curve of olmesartan medoxomil in bulk form was linear from 0.5-10 μg ml-1 and 0.05-1 mg ml-1 with mean percentage accuracy 99.97 ± 1.085 % and 100.35 ± 1.060 % for HPLC and HPTLC methods, respectively. The two proposed methods were successfully applied for the determination of olmesartan medoxomil in drug substance and in drug product. Methods validation was tested for linearity; accuracy; precision; selectivity and robustness, according to USP guidelines.