Serum Magnesium and Related Factors in Long-Term Renal Transplant Recipients: An Observational Study

Low serum magnesium (MgS) is a known risk factor for cardiovascular and mineral bone disease. In renal transplant recipients (RTRs), low MgS levels have been related to higher glomerular filtration rates (GFR) and with calcineurin inhibitors, particularly tacrolimus. We aimed to evaluate MgS in renal transplant recipients with over 1 year of follow-up to establish related risk factors and the impact of the use of cyclosporine versus tacrolimus.

Cross-sectional study of 94 RTRs with more than 12 months of follow-up. Hypomagnesemia was defined as serum magnesium level <1.5 mg/dL.

Hypomagnesemia was found in 5.3% of patients. MgS showed a negative correlation with creatinine clearance. A positive correlation between MgS with urinary magnesium and phosphorus was found. Cyclosporine versus tacrolimus analysis did not show a significant difference regarding MgS when considering all the population and the subgroup of patients with GFR >45 mL/min/1.73 m². On the subgroup with GFR <45 mL/min/1.73 m², those on tacrolimus had lower MgS than those on cyclosporine, but those same patients presented with significantly different GFR, higher in the tacrolimus subgroup.

Hypomagnesemia has a low prevalence in RTRs with more than 1 year of follow-up. MgS levels evidenced a strong correlation with GFR. A significant difference on MgS levels between patients on tacrolimus and cyclosporine was found only when considering GFR <45 mL/min/1.73 m², in which patients on tacrolimus had significantly higher GFR than patients on cyclosporine, which may explain these results.