Determination of in vitro Dissolution Profiles of Amlodipine Besylate and Olmesartan Medoxomil Using a New “HPLC Method”

The aim of this study was to develop an HPLC method for simultaneous determination of these active compounds and to apply this method to determine the dissolution of AML and OLM from a commercially available tablet. Valsartan (VAL) was used as an internal standard (IS). Separation of AML, OLM and VAL was performed using Phenomenex C18 column (Luna 5 μ, 100A, 250x4.6 mm; California, USA) protected with a Phenomenex C18 guard column (4.0x3.0 mm; California, USA). The chromatographic separation operated isocratically at room temperature using a mobile phase consisted of phosphate buffer (pH 4.0, 0.04 mol/L):methanol:acetonitrile (40:45:15, v/v/v) delivered at a flow rate of 0.8 mL/min and injection volume was 10 μL. The diode array detector was set at 234 nm and 205 nm wavelengths for the quantification of AML and OLM respectively. In vitro dissolution studies revealed that 85% of the labeled amounts of AML and OLM were released within 25 min from their fixed combination tablet dosage form. The developed HPLC method was validated according to the ICH guidelines and it is proposed for dissolution studies of the combination dosage forms of these compounds.