Bioequivalence of nifedipine softgel and capsule in healthy Chinese volunteers by liquid chromatography–mass spectrometry

The study aimed to compare and evaluate the bioequivalence of Calcigard-10 softgel and Adalat 10 capsule in healthy Chinese volunteers in a randomized, two-way cross over study design with a washout period of 7 days. A sensitive and reproducible electro-spray ionization liquid chromatography-mass spectrometry (ESI-LCMS) assay was developed and validated to determine nifedipine in human plasma using nitrendipine as internal standard. Nifedipine and nitrendipine were extracted from plasma using liquid-liquid extraction with methylene chloride as extraction solvent. The separation was performed by a Diamonsil ODS column (150 x 4.6 mm, 5 microm). The mobile phase was consisted of acetonitrile-5 mM ammonium acetate (52:48, v/v), delivered at flow rate of 1 mL/min. The 90% confidence intervals for the ratio values of logarithmic transformed Cmax and AUC were calculated to evaluate the bioequivalence of two preparations. The values of Cmax (92.3-112.7%), AUC0-t (84.5-95.1%) and AUC0-inf (84.4-95.5%) are within the interval criterion of 70-143% for Cmax and 80-125% for AUC. The Calcigard-10 softgel and Adalat 10 capsule are bioequivalent.