The impact of (1 : 1) cyclosporine A conversion to its microemulsion formulation on the kidney function of patients with cardiac allografts

Due to the large variations in the absorption and bioavailability of conven tional cyclosporine A (CyA), 1:1 (mg:mg) conversion to its microemulsion fo rmulation (Neoral) has been advocated in transplant recipients. However, th e renal hazards and biochemical effects of such conversions are not known i n cardiac transplant recipients. In this study, 68 cardiac transplant recip ients who were receiving conventional CyA, for a period of 61.3 +/- 36.0 (m ean +/- standard error (SE)) months, were switched to the microemulsion for mulation (Neoral). The biochemical and renal function tests were evaluated at 1, 3, 6, 9 and 12 months pre- and post-conversion of CyA. The results ob tained post-conversion were compared with those of the baseline (pre-conver sion). Serum creatinine and uric acid levels significantly increased post-c onversion to the microemulsion formulation. One patient required discontinu ation of the microemulsion in an attempt to reverse severe renal failure. I n spite of a significant decrease in the microemulsion dose at 6, 9 and 12 months, there was a significant increase in the whole blood CyA trough leve ls at 9 and 12 months of conversion. There was no significant change in blo od pressure, serum total cholesterol or potassium post-conversion. Our resu lts suggest that after 1:1 (mg:mg) conversion of CyA to its microemulsion f ormulation, there will be a significant rise in serum creatinie, uric acid and whole blood trough CyA levels necessitating significant dose reduction. This effect is probably due to the markedly improved absorption and bioava ilability of the latter.