Magnesium
Pharmacology
Magnesium is the fourth most common cation in the body and the second most abundant intracellular cation after potassium. Magnesium plays an essential role as an enzymatic cofactor in a number of biochemical pathways, including energy production from adenosine triphosphate (ATP).
Magnesium has a direct effect on the Na+/K+-ATPase pump in both cardiac and nerve tissues. Further, magnesium has some calcium-blocking activity and may indirectly antagonize digoxin at the myocardial Na+/K+-ATPase pump.
Magnesium modifies skeletal and smooth-muscle contractility. Infusions can cause vasodilation, hypotension, and bronchodilation. It can reduce or abolish seizures of toxemia.
Magnesium is primarily an intracellular ion, and only 1% is in the extracellular fluid. A low serum Mg level (<1.2 mg/dL) may indicate a net body deficit of 5000 mg or more.
Hypomagnesemia can be associated with a number of acute or chronic disease processes (malabsorption, pancreatitis, diabetic ketoacidosis). It may result from chronic diuretic use, cisplatin administration, or alcoholism. It is a potentially serious, life-threatening consequence of hydrofluoric acid poisoning.
Indications
Replacement therapy for patients with hypomagnesemia.
Torsade de pointes ventricular tachycardia (See V. Ventricular dysrhythmias).
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