DETERMINATION OF NIFEDIPINE IN RAT PLASMA USING HPLC-UV DETECTOR: A SIMPLE METHOD FOR PHARMACOKINETICS AND ORAL BIOAVAILABILITY STUDIES

Objective: To develop and validate a high-performance liquid chromatographic method (HPLC) for the determination of nifedipine (NFD) concentration in rat plasma.Methods: 1.5 mol of sodium hydroxide solution was added to each plasma sample, followed by the addition of an extraction solvent based on n-hexane and dichloromethane (70: 30, v/v). The organic layer was transferred and evaporated to dryness under nitrogen flow. The residue was reconstituted with 0.5 mol of acetic acid, followed by the addition of n-hexane. After centrifuging the mixture, the supernatant organic layer of n-hexane was discarded, and the aqueous solution was injected onto the HPLC using A Phenomenex Luna-C18 reversed phase analytical column (250 x 4.6 mm, 5 µm). The mobile phase consisted of 0.01 mol aqueous ammonium formate: methanol: acetonitrile (55: 43: 2, v/v) with pH adjusted to 4.9 using formic acid. The flow rate was 0.8 ml/min; UV detector set at 235 nm and the samples were quantified using the peak area.Results: A well-resolved NFD peak was achieved free of interference from endogenous compounds in rat plasma. Recovery of NFD was more than 93 % over concentrations ranged from 5.00 to 200 ng/ml. The limit of quantification (LOQ) of this assay was 6 ng/ml and, intra-and inter-day coefficient of variation (CV) were 5.75 % and 7.93 %, respectively. NFD was found to be stable in rat plasma after being stored at -30 °C over 90 d.Conclusion: The stability, sensitivity, specificity and reproducibility of this method make it suitable for the determination of NFD plasma concentration in pharmacokinetics and oral bioavailability studies