Hypomagnesemia in Pediatric Heart Transplant Patients Treated with Tacrolimus

We aimed to investigate the frequency of hypomagnesemia and urinary magnesium excretion in pediatric heart transplant recipients.

In this study, 22 pediatric patients who underwent heart transplanted at a single center between March 2014 and April 2015 and who were treated with oral tacrolimus were analyzed prospectively. Serum magnesium, creatinine, and tacrolimus levels and total amount of urinary magnesium excretion were measured. Serum tacrolimus levels were measured 12 hours after the last dose of tacrolimus.

Our patient group included 11 boys (50%) and 11 girls (50%) with a mean age of 16.72 ± 4.78 years. Serum tacrolimus levels were in the therapeutic range, with a mean of 1.48 ± 0.13 ng/mL (range, 1.2-1.69 ng /mL), mean fractional magnesium excretion was 8.59 ± 5.9% (range, 3%-22%), and 24-hour urinary magnesium excretion was 90.2 ± 62.95 mg/d. Hypermagnesuria was assessed in 80% of patients. We found 24-hour urinary magnesium excretion to be higher than normal in 27% of patients. There was no association between serum tacrolimus levels and serum magnesium levels or urinary magnesium excretion.

Serum magnesium levels should be periodically measured in pediatric heart transplant patients treated with tacrolimus.