Magnesium in chronic kidney disease: unanswered questions.

BACKGROUND: Magnesium ion is critical for life and is integrally involved in cellular function and a key component of normal bone mineral. In health, the kidneys, gastrointestinal tract and bone are responsible for maintaining serum magnesium concentrations in the normal range and magnesium balance. Most clinical disorders involving magnesium, other than chronic kidney disease (CKD), result in hypomagnesemia, either from gastrointestinal or kidney losses. CKD and particularly end-stage kidney disease is the only clinical condition where sustained hypermagnesemia may occur and net magnesium balance may be positive.
METHODS: This review will focus on normal magnesium homeostasis and review the literature in CKD with a particular focus on end-stage kidney disease and the potential role of magnesium as a phosphate binder and in cardiovascular and bone health.
RESULTS: A number of small to medium-size interventional trials have shown that magnesium-based compounds can serve as effective phosphate binders. Observational studies suggest that higher serum magnesium concentrations in dialysis patients may improve survival and may slow the progression of vascular calcification. While a few small prospective trials support these findings, no large or long-term studies are available.
CONCLUSIONS: Magnesium balance remains poorly understood in patients with end-stage kidney disease. While observational and small randomized trials suggest that exogenous administration may be useful as a phosphate binder and may have protective cardiovascular effects in terms of both arrhythmias and vascular calcification, large randomized trials are needed to test these hypotheses.