Hypomagnesemia generally results from a derangement in renal or intestinal handling of magnesium and is classified as primary (hereditary) or secondary (acquired). Hereditary causes include both disorders of absorption (rare) and those of renal loss (e.g., Bartter's and Gitelman syndromes). Secondary causes are much more common, with renal losses being due to volume expansion, hypercalcemia, osmotic diuresis, loop diuretics, alcohol, aminoglycosides, cisplatin, cyclosporine, and amphotericin B, and gastrointestinal losses most commonly resulting from vomiting and diarrhea.
Treatment: Hypomagnesemia For mild deficiency, oral replacement in divided doses totaling 20-30 mmol/d (40-60 meq/d) is effective, although diarrhea may result. Parenteral magnesium administration is usually needed for serum levels <0.5 mmol/L (<1.2 mg/dL), with a continuous infusion of magnesium chloride IV to deliver 50 mmol/d over a 24-h period (dose reduced by 50-75% in renal failure). Therapy may be required for several days in order to replete tissue magnesium stores; serum Mg should be monitored every 12-24 h during treatment. Other electrolyte disturbances should be treated simultaneously. Pts with associated seizures or acute arrhythmias can be given 1-2 g of magnesium sulfate IV over 5-10 min. |
Section 13. Endocrinology and Metabolism