Absorption and disposition of colloidal drug delivery systems. I. High-performance liquid chromatographic (HPLC) analysis of a cyclosporin emulsion.

The amount of cyclosporin A in an oil-in-water emulsion drug delivery system was determined by HPLC. The direct extraction and analysis of an intact emulsion were compared to the analysis of a cracked emulsion and an olive oil solution of the drug. The intra- and interday variability for the intact emulsion was less than 10% from 35 to 150 micrograms/ml, with recovery of 94%. Comparison of the assay results obtained with the emulsion and the olive oil solution gave a highly correlated regression line with a small intercept and a slope close to unity. Thus, the direct extraction and HPLC analysis of drugs in emulsions may be a viable approach to evaluate drug content.