Trough levels and concentration time curves of cyclosporine in patients undergoing renal transplantation.

We determined the AUC of cyclosporine (24 hours) nonspecifically by RIA and specifically by HPLC after an oral and an intravenous dose of cyclosporine in 58 patients undergoing renal transplantation. The RIA/HPLC concentration ratio of cyclosporine changed continuously during the first 12 hours after administration. The ratio was higher after oral than after intravenous administration and varied from patient to patient. The predictive value of trough levels for the corresponding AUCs was better when trough levels were assessed 24 than 12 hours after administration. Trough levels assessed by RIA poorly predicted AUCs measured specifically by HPLC. Therefore if, in the future, therapeutic cyclosporine monitoring has to be improved, trough levels should be assessed 24 hours after the last dose by means of a specific HPLC method.