Validated HPLC method for determination of amlodipine in human plasma and its application to pharmacokinetic studies

A rapid, simple and sensitive high-performance liquid chromatography (HPLC) method has been developed for quantification of amlodipine in plasma. The assay enables the measurement of amlodipine for therapeutic drug monitoring with a minimum detectable limit of 0.2 ng ml⁻¹. The method involves simple, one-step extraction procedure and analytical recovery was about 97%. The separation was performed on an analytical 125 × 4.6 mm i.d. Nucleosil C₈ column. The wavelength was set at 239 nm. The mobile phase was a mixture of 0.01 M sodium dihydrogen phosphate buffer and acetonitrile (63:37, v/v) adjusted to pH 3.5 at a flow rate of 1.5 ml min^–1. The calibration curve was linear over the concentration range 0.5–16 ng ml⁻¹. The coefficients of variation for inter-day and intra-day assay were found to be less than 10%.