Cyclosporin A: correlation between HPLC and RIA serum levels.

Serum levels of cyclosporin A were analysed in parallel with an HPLC and a RIA method for six patients who received repeated intramuscular and oral doses of this immunosuppressive drug after bone marrow transplantation. A good correlation was found between both methods with a similar time course of the serum curves. Due to cross-reacting metabolites, the values from the RIA assay were on average 30 to 100% higher than with the HPLC assay which is specific for the parent drug.