Stability indicating RP-HPLC method for simultaneous determination of amlodipine and benazepril hydrochloride from their combination drug product.

A stability indicating reversed-phase HPLC method has been developed and subsequently validated for simultaneous estimation of amlodipine (AM) present as amlodipine besylate (AB), and benazepril hydrochloride (BH) from their combination product. The proposed RP-HPLC method utilizes a Zorbax SB C18, 5 microm, 250 mm x 4.6 mm i.d. column, mobile phase consisting of phosphate buffer and acetonitrile in the proportion of 65:35 (v/v) with apparent pH adjusted to 7.0, and UV detection at 240 nm using a photodiode array detector. AB, BH, and their combination drug product were exposed to thermal, photolytic, hydrolytic, and oxidative stress conditions, and the stressed samples were analysed by the proposed method. Peak homogeneity data of AM and BH peaks obtained using photodiode array detector, in the stressed sample chromatograms, demonstrated the specificity of the method for their estimation in presence of degradants. The described method was linear over a range of 6-14 microg/ml for AM and 12-28 microg/ml for BH. The mean recoveries were 99.91 and 100.53% for AM and BH, respectively. F-test and t-test at 95% confidence level were used to check the intermediate precision data obtained under different experimental setups; the calculated value was found to be less than critical value.