Is serum creatinine a reliable expression of an adequate cyclosporine immunosuppression?

In 13 renal transplant patients with an excellent graft function, but concomitant abnormal T6 CsA plasma levels (CsA plasma level, 6 hours after oral administration of the drug), dose adjustments of CsA were performed until a normal T6 was achieved. A significant decrease of serum creatinine values was obtained after dose modification. Prophylactic monitoring of CsA immunosuppression by T6 could be a means of avoiding nephrotoxicity or undertreatment in patients with acceptable serum creatinine levels and unsuspected drug related renal dysfunction.