RAPID, SENSITIVE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC METHOD FOR THE DETERMINATION OF CYCLOSPORINE-A AND ITS METABOLITES M1, M17 AND M21

Cyclosporin A (CyA) and its metabolites seem to have nephro-, hepato- and neurotoxic side effects. Immunosuppressive therapy is a narrow pat h between the risk of rejection by underimmunosuppression and toxic or gan damage by overdosage. Thus CyA dosage must be calculated to avoid the risks of organ rejection through underdosage and toxic organ damag e through overdosage or accumulation of metabolites. In routine monito ring of CyA therapy, it can be important to measure not only the paren t drug but also the metabolites. We describe a rapid and isocratic hig h-performance liquid chromatographic method for measurement of CyA and its metabolites M1, M17 and M21 in whole blood. CyA was detected by u ltraviolet absorption at 212 nm with a CN analytical column maintained at 50 degrees C and recycling of hexane-isopropanol as mobile phase f or improved long-term column stability and efficiency. The minimum det ectable concentration of CyA and the three metabolites was 10 ng/ml bl ood. Our modified HPLC method for the determination of CyA and its met abolites is a simple (isocratic), rapid (the retention times were 7.1 min for CYD, internal standard, 8.9 min for CyA, 11.0 min for M21, 12. 9 min for M17 and 16.3 min for M1) and economical method suitable for measuring the concentration of the major metabolite, M17, and for rout ine monitoring of CyA-treated patients.