Effects of antioxidant supplementation on blood cyclosporin A and glomerular filtration rate in renal transplant recipients

Background. Transplant recipients have elevated oxidative stress, which has prompted suggestions that supplementary antioxidants may be beneficial. However, only a small number of clinical trials have investigated antioxidant supplementation in transplant recipients, with very few data on their effects on patients ' immunosuppressive therapy. Methods. A randomized placebo-controlled single-blind crossover trial was conducted in 10 renal transplant recipients (RTRs) taking cyclosporin A (CsA) as part of their immunosuppressive therapy. Each phase of the trial lasted 6 months, with a 6 month wash-out period in between. During one of the phases, patients consumed a tablet twice per day which delivered 400 IU/day of vitamin E, 500 mg/day of vitamin C and 6 mg/day of P-carotene. Results. During antioxidant supplementation, there was no change in CsA dose. Antioxidant supplementation resulted in a significant decrease (P < 0.05) in blood trough CsA by 24% (mean +/- SD, pre-127.3 +/- 38.9, post- 97.2 +/- 30.7 mu g/ml) compared with no change while taking the placebo (pre- 132.2 +/- 50.6, post- 138.6 +/- 56.0 mu g/ml). The glomerular filtration rate was significantly (P < 0.05) improved by 12% during antioxidant supplementation (pre- 66.9 +/- 20.7, post- 75.0 +/- 20.1 ml/min/1.72m(2)), with no change during the placebo phase (pre- 66.+/- 8 11.8, post-66.7 +/- 16.1 ml/min/1.72 m(2)). There were no significant differences (P > 0.05) in markers of oxidative stress (malondialdehyde, susceptibility of plasma to oxidation) or plasma antioxident enzymes. Conclusion. In CsA-treated RTRs, antioxidant supplementation decreased blood CsA, which may affect adequacy of immunosuppression.