Measurement of amphotericin B in serum or plasma by high-performance liquid chromatography

A high-performance liquid chromatographic method for the analysis of amphotericin B in 25 microliters of serum or plasma is described. The procedure involves the addition of the internal standard, p-nitrobenzyloxyamine, to the sample followed by a precipitation of protein with acetonitrile. The supernatant is directly injected into a chromatograph attached to a reversed-phase mu Bondapak (Waters) column containing C18 packing. The mobile phase is a 60 : 40 mixture of a sodium acetate buffer (10 mM, pH 7.0)--acetonitrile, and we employ a flow-rate of 1.5 ml/min and a detection wavelength of 405 nm. Total analysis time per sample is 10 min. Coefficients of variation were found to be less than 4% for concentrations less than 2 mg/l. Analytical recoveries were between 75 and 80%. No drug or drug metabolite interference was found. The method will be used to study pharmacokinetic and pharmacodynamic data in a pediatric population.