Clinician Fact Sheet: Magnesium
Clinician Fact Sheet: Magnesium
June 2001; Volume 4; S2-S2
A relatively rare disorder that may be caused by chronic diarrhea, chronic vomiting, hyperaldosteronism, and celiac disease, hypomagnesemia only occurs in about 2% of the general population. However, incidence rates jump to 10-20% in hospitalized patients and 50-60% in intensive care unit patients. Increased rates also are found among alcoholics (30-80%) and diabetics (25%).
Dietary Reference Intakes (DRI)
- 30 mg/d for children 0-6 mo 360 mg/d for girls 14-18 y
- 75 mg/d for children 7 mo-1 y 400 mg/d for men 19-30 y
- 80 mg/d for children 1-3 y 310 mg/d for women 19-30 y
- 130 mg/d for children 4-8 y 420 mg/d for men 30 y and older
- 240 mg/d for children 9-13 y 320 mg/d for women 30 y and older
- 410 mg/d for boys 14-18 y
Food Sources
Dietary sources of magnesium include leafy green vegetables, nuts, whole grains, dried peas and beans, dairy products, fish, meat, and poultry.
Mechanism of Action
— Magnesium is the second most plentiful cation in the intracellular fluid and the most plentiful cation in the body.
— As much as 50% of the magnesium in the body is found in bone.
— Magnesium plays an essential role in more than 300 fundamental cellular reactions and is important to normal bone structure.
— Required for the formation of cyclic AMP, magnesium is involved in ion movements across cell membrane, protein synthesis, and carbohydrate metabolism.
— Magnesium is a component of GTPase and a cofactor for Na-K ATPase, adenylate cyclase, and phosphofructokinase.
— Extracellular magnesium is critical to maintaining nerve and muscle electrical potentials and transmitting impulses across neuromuscular junctions.
— Absorption of dietary magnesium takes place mainly in the ileum and is excreted in stool and urine. Regulation of serum magnesium is controlled by the kidneys.
Clinical Uses
— To treat and prevent hypomagnesemia.
— To treat symptoms of gastric hyperacidity.
— To relieve constipation and to prepare the bowel for surgical or diagnostic procedures.
— To treat cardiovascular diseases, including angina, arrhythmias, hypertension, coronary heart disease and hyperlipidemia, low high-density lipoprotein levels, mitral valve prolapse, and myocardial infarction.
— To treat leg cramps, diabetes, kidney stones, migraine, osteoporosis, premenstrual syndrome, altitude sickness, urinary incontinence, and preeclampsia.
— To prevent hypomagnesemia in patients receiving total parenteral nutrition.
— In combination with malic acid, to treat symptoms of fibromyalgia.
— Topically, to treat infected skin ulcers, boils, and carbuncles; and to speed wound healing.
— Parenterally, to treat acute hypomagnesemia associated with pancreatitis, malabsorption disorders, cirrhosis, preeclampsia, and eclampsia.
— To increase energy and endurance in athletes.
— Intravenously, to control seizures associated with epilepsy, glomerulonephritis, or hypothyroidism when low serum magnesium levels are present.
— Intravenously, to treat cardiac arrest, atrial and ventricular arrhythmias, acute exacerbations of asthma, chronic obstructive pulmonary disease, migraine, neuropathic pain, postoperative pain, cerebral edema, and tetanus.
— Intravenously, to prevent arrhythmias after myocardial infarction and uterine contractions in preterm labor.
— To treat attention deficit hyperactivity disorder associated with magnesium deficiency.
Formulations
- Magnesium gluconate and chloride are preferred for oral replacement because there is less risk of diarrhea with these formulation.
- Magnesium oxide has an increased risk of diarrhea when taken orally.
- Magnesium carbonate may not be soluble enough to adequately replace magnesium levels.
- Magnesium citrate, sulfate, and hydroxide salts are recommended to relieve constipation.
- Magnesium carbonate, hydroxide, oxide, and trisilicate are most commonly used as antacids.
Adverse Effects/Toxicity
— Although safe at recommended amounts, oral magnesium can cause gastrointestinal irritation, nausea, vomiting, and diarrhea. Higher intakes may cause hypermagnesemia (most commonly in renal patients taking magnesium) with symptoms that include: thirst, hypotension, drowsiness, confusion, loss of tendon reflexes, muscle weakness, respiratory depression, cardiac arrhythmias, coma, cardiac arrest, and death.
— Prolonged use of magnesium-containing antacids may cause chronic diarrhea leading to fluid and electrolyte imbalances.
— Urticaria has been reported with IV administration.
— Prolonged topical use to treat boils or carbuncles can cause damage to surrounding skin.
Interactions/Nutrient Depletion
— Symptoms of magnesium deficiency include convulsions, confusion, muscle weakness, and abnormal muscle movements.
— Concomitant use of boron can increase magnesium levels.
— Concomitant use of calcium and fiber supplements can decrease magnesium absorption. Inadequate vitamin D levels also can affect magnesium absorption.
— Concomitant use of fluoroquinolones can decrease magnesium absorption.
— Digoxin, loop diuretics, thiazide diuretics, estrogens, penicillamine, aminoglycosides, amphotericin-B, cisplatin, cyclosporin, and pentamidine can decrease serum magnesium levels.
— Excretion-enhancing drugs can decrease the effects of magnesium; excretion-reducing drugs can increase the effects of magnesium.
— Concomitant use of nifedipine and intravenous magnesium sulfate can cause profound hypotension or neuromuscular blockade.
— Magnesium can potentiate the effects of skeletal muscle relaxants.
— Magnesium may interfere with the results of the following tests: serum alkaline phosphatase, serum angiotensin converting enzyme, serum calcium, plasma cortisol, urine diagnex blue, plasma parathyroid hormone, serum testosterone, blood pressure, and electrocardiograms.
— The elderly have an increased risk of hypomagnesemia, which often is accompanied by low potassium levels.
— Magnesium is contraindicated in people with heart block and should be used cautiously in people with renal disease.
— Intestinal magnesium absorption can be decreased in bile insufficiency states, gastrointestinal infections, gluten enteropathy, immune diseases with villous atrophy, inflammatory bowel disease, intestinal fistulas, lymphectasia, primary idiopathic hypomagnesemia, radiation enteritis, and sprue.
Resources
Pelton R, et al. Drug-Induced Nutrient Depletion Hand-book. Hudson, OH: Lexi-Comp; 1999.
Magnesium. Facts about Dietary Supplements. Office of Dietary Supplements. National Institutes of Health. Available at: www.cc.nih.gov/ccc/supplements/magn.html. Accessed: May 11, 2001.
Natural Medicines Comprehensive Database [database online]. Stockton, CA: Therapeutic Research Center, Inc., 2000.
June 2001; Volume 4; S2-S2
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