High-performance liquid chromatographic determination of liposomal nystatin in plasma and tissues for pharmacokinetic and tissue distribution studies

A reliable reversed-phase high-performance liquid chromatographic method wa s developed for the determination of liposomal nystatin in plasma. Nystatin is extracted by 1:2 (v/v) liquid-liquid extraction with methanol. separati on is achieved by HPLC after direct injection on a mu Bondapak(TM) C-18 ana lytical column with a mobile phase composed of 10 mM sodium phosphate, 1 mM EDTA, 30% methanol and 30% acetonitrile adjusted to pH 6. Detection is by ultraviolet absorbance at 305 nm. Quantitation is based on the sum of the p eak area concentration of the two major isomers of nystatin, which elute at 7.5-8.5 and 9.5-10.5 min. The assay was linear over the concentration rang e of 0.05 to 50 mu g/ml. The lower limit of quantitation was 0.05 mu g/ml, sufficient for investigating the plasma pharmacokinetics of liposomal nysta tin in preclinical studies. Accuracies and intra- and inter-day precision s howed good reproducibility. With minor modifications, this method also was used for assaying nystatin in various non-plasma body fluids and tissues. ( C) 1999 Published by Elsevier Science B.V. All rights reserved.