Effect of probucol on the blood concentration of cyclosporin A in patients with nephrotic syndrome: a case study with a microemulsion formulation (Neoral)

Cyclosporin A(CyA) is used frequently in the treatment of steroid-resistant or recurrent cases with nephrotic syndrome. Recently, a new microemulsion formulation of CyA(Neoral) has been developed and used preferably because of a more stable bioavailability than an oily formulation(Sandimmun). Nephrotic syndrome accompanies hyperlipidemia, and probucol is used in cases showing inadequate effects or some adverse reactions under therapy with HMG-CoA reductase inhibitors. We reported previously that combined use of probucol caused a decrease in blood concentrations of CyA to about half of those without probucol. In the present study, we evaluated the influence of probucol on the blood concentrations of CyA in patients with nephrotic syndrome following Neoral. Coadministration of Neoral and probucol decreased the blood concentrations of CyA to approximately 75% of the levels before combined use. The change of blood CyA concentrations appeared to be smaller compared to those in cases with Sandimmun. Based on the present findings, we suggest that Neoral should be used preferentially instead of Sandimmun when the concomitant use of probucol is required, and that optimal dose adjustment of CyA is needed by frequent monitoring of CyA blood concentrations.