High-Performance liquid chromatographic analysis of lactone and hydroxy acid of new antitumor drug, DX-8951 (exatecan), in mouse plasma.

A sensitive high-performance liquid chromatographic (HPLC) method has been developed and validated for the determination of lactone and total drug (lactone plus hydroxy-acid) of DX-8951 in mouse plasma. Solid-phase extraction by C18 cartridge separated lactone from total drug of DX-8951. Analysis was performed using a reverse-phase ODS column with a mobile phase consisting of acetonitrile/0.05 M potassium dihydrogen phosphate (pH 3) (18: 82, v/v) at a flow rate of 1 ml/min. The limits of quantitation of lactone and total drug were 3 ng/ml in plasma and a linear range of determination were observed over the concentration of 3 to 500 ng/ml. This method was applied to pharmacokinetic study in male mice treated with a single intravenous administration of either lactone or hydroxy-acid of DX-8951. The plasma concentrations of lactone from 2 to 6 h after dosing were similar regardless of the form of DX-8951 administered.