Cyclosporin A is an immunosuppressant widely used in therapy for autoimmune diseases or after organ transplantation. This agent, with a large molecular weight consisting of 12 amino acids, is very hydrophobic, so that after oral administration it needs a surfactant or bile acids to be dissolved and be absorbed in the gastrointestinal tract. It was reported that oral cyclosporin A absorption was greatly affected by foods and bile acids.1) Blood concentrations of cyclosporin A should be managed with therapeutic drug monitoring to acquire adequate effectiveness and to avoid adverse effects, since little relationship between dosage and concentration of cyclosporin A has been reported.2) Recently a therapy using a new oral cyclosporin A formulation, microemulsion preconcentrate (MEPC), has been developed.3) The MEPC formulation is highly soluble in water in a state of microemulsion without any surfactant, so that the pharmacokinetics of cyclosporin A is considered to be rarely affected by bile secretion or foods. This formulation achieves smaller variability in the pharmacokinetics of cyclosporin A than a conventional formulation. [4][5][6] Cyclosporin A and another immunosuppressant, tacrolimus, are calcineurin inhibitors, and have hydrophobic properties.2,7) Since both calcineurin inhibitors are mainly eliminated via hepatic metabolism by the P450 3A subfamily, the pharmacokinetics is in general considered to be unaffected in renal failure patients. However, several clinical reports suggested that renal function affects the pharmacokinetics of cyclosporin A.8,9) The oral absorption of cyclosporin A was reduced in rats with renal failure induced by administration of nephrotoxic agents, glycerol and gentamicin.10,11) On one hand, we reported that the bioavailability of tacrolimus was increased by about 35% in rats with renal dysfunction, induced by intraperitoneal injection of cisplatin.12) We hypothesized that the difference of nephrotoxic agents used in the induction of experimental renal dysfunction might influence the effect of acute renal failure on the pharmacokinetics of cyclosporin A or tacrolimus. In addition, Shibata et al. 11) suggested that changes in bile secretion and intestinal transcellular transport might reduce the absorption of cyclosporin A, since their oral formulation was cyclosporin A added to appropriate surfactants, not MEPC.In this study, using a cisplatin-induced ARF model, we examined the effect of ARF on the pharmacokinetics of cyclosporin A after oral administration of the MEPC formulation, and further investigated the mechanisms behind the changes of cyclosporin A pharmacokinetics in ARF rats.
MATERIALS AND METHODS
MaterialsThe cyclosporin A MEPC formulation (Neoral ® capsule) and injection solution (Sandimmun ® injection solution, 50 mg/ml) were obtained from Novartis Pharma K.K. (Tokyo, Japan). Cisplatin (Randa ® injection solution, 0.5 mg/ml) was purchased from Nippon Kayaku Co. Ltd. (Tokyo, Japan). All other chemicals were of the highest purity available.Animals and Induction of Acu...