Quantitative extraction of amphotericin B from serum and its determination by high-pressure liquid chromatography.

Therapeutic concentrations of amphotericin B in serum were measured by reversed-phase liquid chromatography with detection at 386 nm. Complete recovery of the drug and the internal standard from a 1-ml serum sample was achieved by pretreating the sample with guanidine hydrochloride and extracting it with a disposable reversed-phase phenyl extraction column. The method was sensitive to 0.005 micrograms of amphotericin B per ml and linear to at least 5 micrograms/ml. Coefficients of variation were 4.8% within-run and 6.3% between-run.