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Magnesium Chloride

Pronunciation: mag-NEE-zee-um KLOR-ide
Class: Mineral

Trade Names

Chloromag
- Injection, solution, concentrate 20% (elemental magnesium 1.97 mEq/mL)

Pharmacology

Magnesium is an important activator of many enzyme systems, and deficits are accompanied by a variety of functional disturbances.

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Pharmacokinetics

Absorption

Immediately absorbed (IV).

Distribution

Approximately 1% to 2% of total body magnesium is the extracellular fluid space; 30% bound to albumin.

Metabolism

Magnesium is not metabolized.

Elimination

Excreted solely by the kidneys at a rate proportional to the serum concentration and glomerular filtration.

Special Populations

Renal Function Impairment

No data available.

Hepatic Function Impairment

No data available.

Indications and Usage

Electrolyte replenisher in magnesium deficiencies.

Contraindications

Renal impairment; marked myocardial disease; comatose patients.

Dosage and Administration

Magnesium Deficiency
Adults

IV 1 to 40 g daily.

General Advice

  • For IV infusion only. Not for intradermal, IM, subcutaneous, or intra-arterial administration.
  • To prepare IV infusion, use 4 g in 250 mL of dextrose 5% injection.
  • Administer at a rate not exceeding 3 mL/min.
  • Serum magnesium levels should serve as a guide to continued dosage.
  • Have an IV calcium preparation on hand as an antidote.
  • Prior to repeat doses, test for knee-jerk reflexes. If they are absent, no additional magnesium should be given until reflexes return.
  • Incompatibilities: streptomycin, tetracycline, tobramycin.

Storage/Stability

Store at 59° to 86°F.

Drug Interactions

Alcohol, aminoglycosides, amphotericin B, cisplatin, cyclosporine, digitalis, diuretics

Drug-induced renal losses of magnesium can occur. Use with caution and closely monitor magnesium concentrations.

Neuromuscular blocking agents (eg, pancuronium)

Potentiation of neuromuscular blockade. Use with caution. Monitor for respiratory depression. Adjust the neuromuscular blocking agent dose as needed. Be prepared to provide life support.

Nifedipine

The risk of neuromuscular blockade and hypotension may be increased. Closely monitor the clinical response. Be prepared to provide supportive treatment or to discontinue one or both drugs if needed.

Adverse Reactions

Cardiovascular

Sharply lowered BP.

CNS

Stupor.

Metabolic

Hypermagnesemia.

Respiratory

Respiratory depression.

Miscellaneous

Flushing, hypothermia, sweating.

Precautions

Monitor

Monitor serum magnesium levels and the patient's clinical status to guide need for continued dosage. Normal serum concentration is 1.5 to 2.5 or 3 mEq/mL. Monitor levels hourly for patients with severe hypomagnesemia until they reach 1.5 mEq/mL, then every 6 to 12 h for the next 24 h. Once stable, obtain the serum concentration daily. Carefully observe respiration and BP during and after administration of IV magnesium. Maintain urine output at 100 mL every 4 h. Clinical indications of a safe dosage regimen include the presence of the patellar reflex (knee-jerk) and absence of respiratory depression (approximately 16 or more breaths per min). When repeated doses of the drug are given parenterally, knee-jerk reflexes should be tested before each dose; if they are absent, no additional magnesium should be given until they return. The strength of the deep tendon reflexes begins to diminish when magnesium levels exceed 4 mEq/L. Reflexes may be absent at magnesium 10 mEq/L, where respiratory paralysis is a potential hazard.


Pregnancy

Category C .

Lactation

Excreted. The American Academy of Pediatrics classifies magnesium sulfate as compatible with breast-feeding.

Children

Dosing information not provided for children. Some of these products may contain benzyl alcohol. Benzyl alcohol has been associated with a fatal gasping syndrome in premature infants.

Renal Function

Contraindicated in patients with renal impairment.

Aluminum toxicity

Some products contain aluminum. Aluminum may reach toxic levels with parenteral administration if kidney function is impaired. Premature neonates are particularly at risk.

Flushing/Sweating

Administer with caution if either occurs.

Overdosage

Symptoms

Decreased deep tendon reflexes, disappearance of patellar reflex, hypotension, muscle weakness, prolonged PR interval, prolonged QRS complex, prolonged QT interval, respiratory paralysis, sedation, sharp drop in BP.

Patient Information

  • Advise patient that medication will be prepared and administered by a health care provider in a hospital setting.
  • Advise patient to discontinue use and notify health care provider if dizziness, drowsiness, flushing, muscle weakness, or sweating occurs.

Copyright © 2009 Wolters Kluwer Health.

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