Effects of antioxidant supplementation on blood cyclosporine 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 â-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 ìg/ml) compared with no change while taking the placebo (pre- 132.2±50.6, post- 138.6±56.0 ìg/ml). The glomerular filtration rate was significantly (P<0.05) improved by 12% during antioxidant supplementation (pre- 66.9±20.7, post- 75.0±20.1ml/min/ 1.72 m2), with no change during the placebo phase (pre- 66.8±11.8, post- 66.7±16.1 ml/min/1.72 m2). There were no significant differences (P>0.05) in markers of oxidative stress (malondialdehyde, susceptibility of plasma to oxidation) or plasma antioxidant enzymes. Conclusion. In CsA-treated RTRs, antioxidant supplementation decreased blood CsA, which may affect adequacy of immunosuppression.