Skeletal muscle magnesium content during cyclosporin and azathioprine treatment in renal transplant recipients.

Cyclosporin treatment is often accompanied by hypomagnesaemia and renal magnesium wasting, but it is unknown whether cyclosporin induces tissue magnesium depletion. Magnesium status is best evaluated by measurement of skeletal muscle magnesium content. The purpose of the present study was to evaluate whether skeletal muscle magnesium content was reduced during cyclosporin treatment. In two groups of renal transplant recipients treated with either cyclosporin and prednisolone (group Cy, n = 13) or azathioprine and prednisolone (group Az, n = 17) skeletal muscle content of magnesium, serum magnesium, and urinary excretion of magnesium were determined, and the relationships between skeletal muscle magnesium content, serum magnesium and urinary magnesium were analysed. Skeletal muscle magnesium content did not differ significantly between groups; 7.93 mumol/g wet weight (median) in group Cy versus 8.38 mumol/g wet weight in group Az. Serum magnesium was significantly (P < 0.01) lower in group Cy (0.71 mmol/l) than in group Az (0.82 mmol/l). The urinary excretion of magnesium did not differ between the groups. Skeletal muscle magnesium did not correlate with either serum magnesium or urinary magnesium excretion in group Cy or group Az. Thus the present study indicates that cyclosporin-treated patients are not magnesium depleted, and serum magnesium in these patients does not reflect the skeletal muscle content of magnesium.