Renal handling of magnesium in transplanted children under cyclosporin A treatment.

We investigated the renal handling of magnesium in 12 transplanted children under cyclosporin A treatment during the early period after transplantation. We also studied 30 children treated with cyclosporin A 2 years after renal transplantation and compared the results with those of 22 children treated with azathioprine and prednisolone 2-4 years after transplantation. Twenty-two children with chronic renal failure and 10 healthy children served as controls. During the 1st week after transplantation, the mean serum magnesium level dropped to 0.54 +/- 0.14 mmol/l and was accompanied by a high fractional magnesium clearance. During this period two patients showed generalized convulsions. After magnesium substitution, serum levels increased gradually and normalized 4 months later. Fractional magnesium clearance remained slightly elevated due to lower glomerular filtration rates. One to four years after transplantation there were no statistically significant differences in serum levels, clearance, excretion and fractional clearance of magnesium between patients treated with cyclosporin A and those receiving azathioprine. There was a linear regression between magnesium clearance and creatinine clearance and an inverse exponential correlation between fractional magnesium clearance and creatinine clearance. We conclude that cyclosporin A treatment after transplantation has no major effect on the renal handling of magnesium in kidney transplants. The observed changes in serum magnesium levels and fractional clearance are probably due to tubular cell damage early after transplantation and to high doses of furosemide.