Development of Validated Bioanalytical HPLC-UV Method for Simultaneous Estimation of Amlodipine and Atorvastatin in Rat Plasma

A simple, economical and robust analytical high-performance liquid chromatography-ultraviolet method was developed and validated for simultaneous chromatographic elution of two cardiovascular drugs viz. amlodipine and atorvastatin in biological fluid for the first time. Only two liquid chromatography–mass spectrometry/mass spectrometry methods are available in literature for quantitation of selected pair of analytes. The bioanalytical method was developed in rat plasma by using Thermo beta-basic C(18) (100×4.6 mm, 5 μm) and mobile phase was composed of dibasic phosphate buffer (pH 3.0):acetonitrile in the ratio of 55:45 at a flow rate of 1 ml/min with ultraviolet detection monitored at 240 nm. The selected chromatographic conditions were found to effectively separate amlodipine (5.1 min) and atorvastatin (12.1 min). The parametric statistics,i.e. correlation coefficient of 0.999, was assessed for both the drugs having linearity over the tested concentration range (0.05 to 10.0 μg/ml) in rat plasma using an unweighted calibration curve. The mean recovery (%) was more than 92.8% for both the drugs using protein precipitation method. The accuracy of samples for six replicate measurements at lower limit of quantitation level was within limit. The method was validated and was successfully applied to the nonclinical pharmacokinetic study of combination tablets containing amlodipine and atorvastatin in six Sprague Dawley rats.