High-performance liquid chromatographic determination of oxodipine enantiomers, a new 1,4-dihydropyridine, applied to stereoselectivity studies in man and dog

A specific and reproducible HPLC method using a Chiral-AGP column and UV detection was developed for the evaluation of the pharmacokinetic profile of oxodipine enantiomers in dog and man. Each enantiomer was determined in plasma in the concentration range 1–400 ng/ml using the internal standard calibration method with linear regression analysis. After extraction of oxodipine and the internal standard at alkaline pH with diethyl ether—n-hexane (50:50, v/v), this method permitted the determination of each enantiomer at levels down to 10 ng/ml in dog plasma and 25 ng/ml in human plasma with sufficient accuracy (relative error <11%, n = 6) and precision (coefficient of variation <16%, n = 6). The extracted plasma volume was 500 μl and after evaporation of the organic phase, the dry residue was dissolved in 100 μl of water—2-propanol; an aliquot of 80 μl was injected into the HPLC system.