Magnesium carbonate for phosphate control in patients on hemodialysis. A randomized controlled trial.
BACKGROUND
Magnesium salts bind dietary phosphorus, but their use in renal patients is limited due to their potential for causing side effects. The aim of this study was to evaluate the efficacy and safety of magnesium carbonate (MgCO(3)) as a phosphate-binder in hemodialysis patients.


METHODS
Forty-six stable hemodialysis patients were randomly allocated to receive either MgCO(3) (n=25) or calcium carbonate (CaCO(3)), (n=21) for 6 months. The concentration of Mg in the dialysate bath was 0.30 mmol/l in the MgCO(3) group and 0.48 mmol/l in the CaCO(3) group.


RESULTS
Only two of 25 patients (8%) discontinued ingestion of MgCO(3) due to complications: one (4%) because of persistent diarrhea, and the other (4%) because of recurrent hypermagnesemia. In the MgCO(3) and CaCO(3) groups, respectively, time-averaged (months 1-6) serum concentrations were: phosphate (P), 5.47 vs. 5.29 mg/dl, P=ns; Ca, 9.13 vs. 9.60 mg/dl, P<0.001; Ca x P product, 50.35 vs. 50.70 (mg/dl)(2), P=ns; Mg, 2.57 vs. 2.41 mg/dl, P=ns; intact parathyroid hormone (iPTH), 285 vs. 235 pg/ml, P<0.01. At month 6, iPTH levels did not differ between groups: 251 vs. 212 pg/ml, P=ns. At month 6 the percentages of patients with serum levels of phosphate, Ca x P product and iPTH that fell within the Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines were similar in both groups, whereas more patients in the MgCO(3) group (17/23; 73.91%) than in the CaCO(3) group (5/20, 25%) had serum Ca levels that fell within these guidelines, with the difference being significant at P<0.01.


CONCLUSIONS
Our study shows that MgCO(3) administered for a period of 6 months is an effective and inexpensive agent to control serum phosphate levels in hemodialysis patients. The administration of MgCO(3) in combination with a low dialysate Mg concentration avoids the risk of severe hypermagnesemia.
Tzanakis
Ioannis P
IP
Department of Nephrology, General Hospital of Chania, 18, Michali Mefa St, Chania-Crete PC 73100, Greece. ioatza@otenet.gr
Papadaki
Antonia N
AN
Wei
Mingxin
M
Kagia
Stella
S
Spadidakis
Vlassios V
VV
Kallivretakis
Nikolaos E
NE
Oreopoulos
Dimitrios G
DG
D000469:Alkaline Phosphatase / Q000097:blood; D002118:Calcium / Q000097:blood; D002119:Calcium Carbonate / Q000627:therapeutic use; D005500:Follow-Up Studies; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000628:therapy*; D008274:Magnesium / Q000009:adverse effects / Q000097:blood / Q000627:therapeutic use*; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000378:metabolism*; D010758:Phosphorus / Q000097:blood*; D012016:Reference Values; D006435:Renal Dialysis; D016896:Treatment Outcome
D010281:Parathyroid Hormone; D010710:Phosphates; C005479:magnesium carbonate; D010758:Phosphorus; D000469:Alkaline Phosphatase; D002119:Calcium Carbonate; D008274:Magnesium; D002118:Calcium