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New Treatments for Hypomagnesemia

Hypomagnesemia is rare in healthy subjects because of the abundance of Mg in the food and water supply. Absorption of ingested Mg occurs in the small intestine, and the kidneys regulate Mg balance.


Causes of Hypomagnesemia

Decreased Mg intake

Increased Mg losses

Alterations in the distribution of Mg

Decreased Magnesium Intake. Protein-calorie malnutrition, prolonged parenteral (Mg-free) fluid administration, and catabolic illness are common causes of hypomagnesemia.

Gastrointestinal Losses of Magnesium. Gastrointestinal losses of Mg may result from prolonged nasogastric suction, laxative abuse, pancreatitis, extensive small bowel resection, short bowel syndromes, biliary and bowel fistulas, enteropathies, cholestatic liver disease, and malabsorption syndromes.

Renal Losses of magnesium

Renal loss of Mg may occur secondary to renal tubular acidosis, glomerulonephritis, interstitial nephritis, or acute tubular necrosis.

Hyperthyroidism, hypercalcemia, and hypophosphatemia may cause Mg loss.

Drugs Associated with Mg Loss. Diuretic agents (furosemide, thiazides) induce hypomagnesemia by increasing Mg excretion. Digitalis, aminoglycoside antibiotics, cyclosporine, methotrexate, amphotericin, pentamidine, ethanol, and calcium are associated with hypomagnesemia.

Alterations in Magnesium Distribution

Redistribution of circulating Mg occurs by extracellular to intracellular shifts, sequestration, hungry bone syndrome, or by administration of glucose, insulin, or amino acids.

Mg depletion occurs during severe pancreatitis, large quantities of parenteral fluids, and pancreatitis-induced sequestration of Mg.

Clinical Manifestations of Hypomagnesemia

Cardiovascular. Ventricular tachycardia, ventricular fibrillation, atrial fibrillation, multifocal atrial tachycardia, ventricular ectopic beats, hypertension, enhancement of digoxin-induced dysrhythmias, and cardiomyopathies.

Neuromuscular and Behavioral. Convulsions, confusion, psychosis, weakness, ataxia, spasticity, tremors, tetany, agitation, delirium, and depression.

ECG Changes. Prolonged PR and QT intervals, ST magnesium segment depression, T wave inversions, wide QRS complexes, and tall T waves.

Concomitant electrolyte abnormalities of sodium, potassium, calcium, or phosphate are common.

Clinical Evaluation

Hypomagnesemia is diagnosed when the serum Mg is less than 0.7-0.8 mMol/L. Symptoms of Mg deficiency occur when the serum Mg concentration is less than 0.5 mMol/L. 24-hour urine collection for magnesium is the first step in the evaluation of hypomagnesemia. In hypomagnesemic states, because of