Serum magnesium: 1.5-2.5 mg/dL (MW: 24.3) Overview Dietary Sources: Average diet provides a daily Mg intake ranging form ~17 to ~ 50 mEq ( 200 - 600 mg). Mg is ubiquitous in food, but it is particularly abundant in dairy products, bread and cereals, vegetables (specially the leafy types), meat, and nuts (specially almonds).
Mg++ is an important ion that is required by the human body in relatively large amounts. It is essential for the optimal function of over 300 key enzymes involved in energy transformation, protein synthesis and nucleic acid metabolism. It is also essential for the stability and normal function of the cell membranes of excitable tissues. Thus, Mg abnormalities can have profound effects on neuromuscular transmission and cardiac conduction. Also, a normal body Mg content is necessary for the maintenance of electrolyte balance particularly for Ca++and K+.
Transplant patients are particularly prone to the development of Mg deficiency due to a direct effect of tacrolimus and cyclosporine on the renal tubules which results in enhanced urinary Mg loss.
Distribution and Balance
Average body Mg content is about 1000 mmoles (14 mmoles / kg of body wt), of which ~50% resides in soft tissues and the remainder in bones. The extracellular space contains <1% of total body Mg. The plasma Mg level normally varies within a relatively wide range (1.5 - 2.5 mEq/L). Clinical laboratories typically measure total plasma Mg, of which ~30% is bound to plasma proteins, ~ 20% is complexed with such ions as phosphate and citrate, and ~50% exists in the ionized (physiologically active) state. Due to the relatively low protein binding, variations in the plasma protein level have little influence on the total plasma Mg concentration. This is unlike the case plasma calcium of which ~45% is protein-bound. To correct for low plasma protein levels:
Although serum Mg may not accurately
reflect the overall body Mg balance, clinical symptoms of Mg deficiency
correlate well with serum Mg. Levels < 1.0 mEq/L usually indicate
significant total body Mg depletion. However, the severity of the
symptoms among patients with similar degrees of hypomagnesemia vary
widely. The so-called Mg retention test should not be used in patients
with renal impairment or in transplant patients receiving cyclosporine
or tacrolimus which cause urinary Mg wasting.
Magnesium Tables (formulations)
National Institutes of Health, U.S. National Library of Medicine,
Provides access to the latest drug monographs submitted to the Food and Drug Administration (FDA). Please review the latest applicable package insert for additional information and possible updates. A local search option of this data can be found here.
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