HPLC method for the determination of nifedipine in rat plasma: development, validation, and application to pharmacokinetic drug-herb interaction study

A simple and rapid high-performance liquid chromatography (HPLC) was developed to determine the plasma level of nifedipine in rats after its single administration and combination with herbs. Nifedipine was extracted with acetonitrile to precipitate protein from plasma samples. The separation was implemented on a C18 column with a mobile phase of acetonitrile: water (63:37, v/v). The calibration curve displayed good linearity in the 30–1000 ng/mL range. The lower limit of quantification (LLOQ) was 30 ng/mL. The intraday and interday assay accuracy and precision met the criteria of validation and study sample analysis. The recovery was found to be 101.89%. Stability studies showed that nifedipine was stable after 12 h at room temperature and 21 days at -20 °C. No significant difference was examined between the pharmacokinetic parameters of nifedipine with or without Gynura procumbens leaf extract. The proposed method was helpful for the pharmacokinetic interaction study of nifedipine combined with herbal in rats.