Simultaneous Estimation of Metformin Hydrochloride and Certain Cardiovascular Drugs with a Pharmacokinetic Study

A validated reversed phase HPLC method has been developed for simultaneous determination of certain cardiovascular drugs in addition to metformin HCl in their tablets and spiked rabbit plasma. The separation was performed on a C-18 column using a step nonlinear gradient elution of a mobile phase system composed of water adjusted to pH 3 with phosphoric acid:acetonitrile:methanol in the following ratios; 95:3.3:1.7, v/v/v; 40:20, v/v/v; and 30:40:30, v/v/v, respectively, to achieve a complete separation of the four drugs: metformin hydrochloride, amlodipine besylate, bezafibrate, and valsartan at 1.3, 8.9, 11.7, and 12.3 minutes, respectively, with a detection wavelength of 230nm. The investigated drugs exhibited a linear relationship between the concentration and the peak area in the range 0.46-32 mu g/mL with good correlation coefficients 0.9955. Detection and quantitation limits were 0.15-0.71 mu g/mL and 0.46-2.15 mu g/mL, respectively. The method was applied successfully for analysis of pure forms, tablets, and spiked rabbit plasma samples of the studied drugs. The developed method was utilized successfully to study the change of pharmacokinetic behavior of bezafibrate upon co-administration of valsartan in rabbit plasma.