An HPLC method for the determination of ng mifepristone in human plasma

An HPLC method was developed and validated for the determination of mifepristone in human plasma. C18 solid-phase extraction cartridges were used to extract plasma samples. Separation was by C18 column; mobile phase, methanol–acetonitrile–water (50:25:25, v/v/v); flow rate, 0.8 ml/min; UV detection at 302 nm. The calibration curve was linear in the concentration range of 10 ng/ml to 20 μg/ml (r = 0.9991). Within- and between-day variability were acceptable. The limit of detection for the assay was 6 ng/ml. Plasma samples were stable for at least 7 days in the state of plasma or residue treated at −20 °C. The method was simple, sensitive and accurate, and allowed to determine ng mifepristone in human plasma. It could be applied to assess the plasma level of mifepristone in women receiving low oral doses of mifepristone.