Impact of cyclosporin immunosuppression on serum magnesium and its fractional excretion in renal transplant recipients.

Objective: To evaluate the effect of cyclosporine (CSA) on serum magnesium and its fractional excretion in renal transplant recipients.
Methods: A cross sectional comparative study on 50 live related renal transplant recipients on CSA therapy with serum creatinine < 2.0 mg/dl and 30 healthy controls. Serum creatinine, magnesium and its fractional excretion and CSA levels were monitored. Patients were followed at 6 months.
Results: The mean serum creatinine in patients was 1.41 +/- 0.42 mg/dl, cyclosporine 210 +/- 66 ng/ml at a dose of 4.8 +/- 1.4 mg/kg/day. The serum magnesium was 1.77 +/- 0.32 mg/dl vs 1.98 +/- 0.17 mg/dl in healthy controls (p < 0.05). Fractional excretion was 5.05 +/- 2.53% in patients vs 2.8 +/- 1.05% in controls (p < 0.05). No correlation was found between CSA levels (100-400 ng/ml) and serum magnesium (r = 0.053) or FEMg% (r = 0.215). Of the 50 recipients 27 (54%) had FEMg% in the control range. At 6 months follow up no difference in CSA levels was found between recipients with FEMg% in the normal range vs those with FEMg > 5%. However, serum creatinine increased from 1.42 +/- 0.30 mg/dl to 1.68 +/- 0.82 mg/dl (p < 0.05).
Conclusion: CSA therapy lowers serum magnesium as compared to healthy controls and there is marked increase in FEMg% in 50% of the patients. Patients with FEMg > 5% developed renal function deterioration. FEMg percent can thus be a good follow up marker of CSA chronic toxicity in stable transplant recipients.