Magnesium levels and magnesium containing phosphate binders in haemodialysis patients

Hippokratia 2011; 15 (Suppl 2): 21-26

E Koulouridis, I. Kostimpa, E. Klonou, I. Koulouridis, B. Tsilimpari, Z. Nikolaidou, X. Goudeli, A. Krokida, E. Liapi, I. Bregova


Background and aim: Sufficient evidence suggests that serum magnesium exerts beneficial effect upon cardiovascular status and arterial calcification among dialysis patients. Magnesium containing salts are as effective as the usual phosphate binders in lowering serum phosphorus in haemodialysis patients and posses the advantage of increasing serum magnesium levels which may play an important role in cardiovascular outcome. The aim of this study was To investigate serum magnesium levels among dialysis patients before and after administration of magnesium containing phosphate binders and its clinical significance.
Patients and Methods: In this prospective cohort we investigated 70 patients (45 men, 25 women) undergoing standard bicarbonate dialysis, thrice weekly (3-4 hours) for longer that 6 months. Age 66.1±13.2 (33-88) years, dialysis duration 62.6±57.9 (7-267) months. Presence of coronary artery disease (CAD) was established by previous history of acute myocardial infarction or coronary angiography. Chronic use (>1 year) of proton pump inhibitors (PPIs) was sought from previous history of the patients. Patients with serum magnesium levels lower than 3 mg/dl were eligible to be administered calcium acetate-magnesium carbonate (CalMag) as phosphate binder. We estimated serum calcium, phosphorus, magnesium and calcium-phosphate product monthly and iPTH every three months. In order to avoid hypermagnesaemia after two months patients receiving CalMag underwent dialysis with low magnesium dialysate (0.75 mEq/L) while the rest continued dialysis with usual magnesium dialysate (1 mEq/L).
Results: Lower magnesium levels were identified among patients with coronary artery disease (p=0.01) as well as among patients chronically receiving proton pump inhibitors (p=0.03). Administration of CalMag showed a considerable increase in the magnesium level (p=0.0004) and a significant decrease of phosphate level (p=0.01). Substitution with low magnesium dialysate (0.75 mEq/L) showed a considerable decrease of serum magnesium level (p=0.005). Variations in the levels of calcium, phosphate and calcium-phosphate product between the individual phosphate binders (PBND) showed no statistically significant difference. The estimated three month cost for the individual phosphate binders was lower for calcium carbonate and CalMag compared to the other phosphate binders.
Conclusions: The results of this study suggest that presence of coronary artery disease and chronic use of PPIs is related to lower serum magnesium levels. Administration of CalMag in haemodialysis patients is related to lower phosphorus levels and increased magnesium levels. Low dialysate magnesium concentration reduces effectively serum magnesium levels. The efficacy of CalMag in lowering serum phosphorus level is comparable with the usual phosphate binders. The lower cost of CalMag suggests its more frequent use in clinical practice among selected patients.