Yes

Antacid; Anticonvulsant, Miscellaneous; Electrolyte Supplement, Parenteral; Laxative, Saline; Magnesium Salt

Treatment and prevention of hypomagnesemia and in seizure prevention in severe pre-eclampsia or eclampsia, pediatric acute nephritis; also used as short-term treatment of constipation, postmyocardial infarction, and torsade de pointes

B

Heart block, serious renal impairment, myocardial damage, hepatitis, Addison's disease

Use with caution in patients with impaired renal function (accumulation of magnesium which may lead to magnesium intoxication); use with caution in digitalized patients (may alter cardiac conduction leading to heart block); monitor serum magnesium level, respiratory rate, deep tendon reflex, renal function when MgSO₄ is administered parenterally

1% to 10%:

Central nervous system: Depressed CNS

Gastrointestinal: Diarrhea

Neuromuscular & skeletal: Blocked peripheral neuromuscular transmission leading to anticonvulsant effects

Serum magnesium levels >5 mg/dL:

Cardiovascular: Flushing

Central nervous system: Somnolence

Serum magnesium levels >12.5 mg/dL:

Cardiovascular: Complete heart block

Respiratory: Respiratory paralysis

Symptoms of overdose usually present with serum level >4 mEq/L

Serum magnesium >4: Deep tendon reflexes may be depressed

Serum magnesium greater than or equal to 10: Deep tendon reflexes may disappear, respiratory paralysis may occur, heart block may occur

Serum level >12 mEq/L may be fatal, serum level greater than or equal to 10 mEq/L may cause complete heart block

I.V. calcium (5-10 mEq) 1-2 g calcium gluconate will reverse respiratory depression or heart block; in extreme cases, peritoneal dialysis or hemodialysis may be required

Decreased effect: Nifedipine decreased blood pressure and neuromuscular blockade

Increased toxicity: Aminoglycosides increased neuromuscular blockade; CNS depressants increased CNS depression; neuromuscular antagonists, betamethasone (pulmonary edema), ritodrine increased cardiotoxicity

Refrigeration of intact ampuls may result in precipitation or crystallization

I.V. is incompatible when mixed with fat emulsion (flocculation), calcium gluceptate, clindamycin, dobutamine, hydrocortisone (same syringe), nafcillin, polymyxin B, procaine hydrochloride, tetracyclines, thiopental

Promotes bowel evacuation by causing osmotic retention of fluid which distends the colon with increased peristaltic activity when taken orally; parenterally, decreases acetylcholine in motor nerve terminals and acts on myocardium by slowing rate of S-A node impulse formation and prolonging conduction time

Oral: Onset of cathartic action: Within 1-2 hours

I.M.: Onset of action: 1 hour; Duration: 3-4 hours

I.V.: Onset of action: Immediate; Duration: 30 minutes

Elimination: Primarily in feces; absorbed magnesium is rapidly eliminated by the kidneys

The recommended dietary allowance (RDA) of magnesium is 4.5 mg/kg which is a total daily allowance of 350-400 mg for adult men and 280-300 mg for adult women. During pregnancy the RDA is 300 mg and during lactation the RDA is 355 mg. Average daily intakes of dietary magnesium have declined in recent years due to processing of food. The latest estimate of the average American dietary intake was 349 mg/day. Dose represented as MgSO₄ unless stated otherwise.

Hypomagnesemia:

Neonates: I.V.: 25-50 mg/kg/dose (0.2-0.4 mEq/kg/dose) every 8-12 hours for 2-3 doses

Children: I.M., I.V.: 25-50 mg/kg/dose (0.2-0.4 mEq/kg/dose) every 4-6 hours for 3-4 doses, maximum single dose: 2000 mg (16 mEq), may repeat if hypomagnesemia persists (higher dosage up to 100 mg/kg/dose MgSO₄ I.V. has been used); maintenance: I.V.: 30-60 mg/kg/day (0.25-0.5 mEq/kg/day)

Adults:

Oral: 3 g every 6 hours for 4 doses as needed

I.M., I.V.: 1 g every 6 hours for 4 doses; for severe hypomagnesemia: 8-12 g MgSO₄/day in divided doses has been used

Management of seizures and hypertension: Children: I.M., I.V.: 20-100 mg/kg/dose every 4-6 hours as needed; in severe cases doses as high as 200 mg/kg/dose have been used

Eclampsia, pre-eclampsia: Adults:

I.M.: 1-4 g every 4 hours

I.V.: Initial: 4 g, then switch to I.M. or 1-4 g/hour by continuous infusion

Maximum dose should not exceed 30-40 g/day; maximum rate of infusion: 1-2 g/hour

Maintenance electrolyte requirements:

Daily requirements: 0.2-0.5 mEq/kg/24 hours or 3-10 mEq/1000 kcal/24 hours

Maximum: 8-16 mEq/24 hours

Cathartic: Oral:

Children: 0.25 g/kg every 4-6 hours

Adults: 10-15 g in a glass of water

Dosing adjustment/comments in renal impairment: Cl_cr <25 mL/minute: Do not administer or monitor serum magnesium levels carefully

MgSO₄ oral solution: Mix with water and administer on an empty stomach

When giving I.V. push, must dilute first and should not be given any faster than 150 mg/minute

Monitor blood pressure when administering MgSO₄ I.V.; serum magnesium levels should be monitored to avoid overdose; monitor for diarrhea; monitor for arrhythmias, hypotension, respiratory and CNS depression during rapid I.V. administration

Serum magnesium:

Adults: 1.5-2.5 mg/dL (1.2-2.0 mEq/L)

Note: Serum magnesium is poor reflection of repletional status as the majority of magnesium is intracellular; serum levels may be transiently normal for a few hours after a dose is given, therefore, aim for consistently high normal serum levels in patients with normal renal function for most efficient repletion

magnesium; protein, calcium (S), potassium (S)

May cause sedation or CNS depression

Concurrent use with psychotropics may produce additive CNS depression

No information available to require special precautions

Magnesium products may prevent gastrointestinal absorption of tetracyclines by forming a large ionized chelated molecule with the tetracyclines in the stomach. Tetracyclines should be given at least 1 hour before magnesium.

Take in divided doses; report diarrhea (>5 stools/day) or changes in mental function to physician, nurse, or pharmacist

Dilute to a maximum concentration of 100 mg/mL and infuse over 2-4 hours; do not exceed 125 mg/kg/hour (1 mEq/kg/hour)

Monitor arrhythmias, hypotension, diarrhea, respiratory and CNS depression during rapid I.V. administration; monitor serum magnesium level to avoid overdosages

Granules: ~40 mEq magnesium/5 g (240 g)

Injection: 100 mg/mL (20 mL); 125 mg/mL (8 mL); 250 mg/mL (150 mL); 500 mg/mL (2 mL, 5 mL, 10 mL, 30 mL, 50 mL)

Solution, oral: 50% [500 mg/mL] (30 mL)

Bohman VR and Cotton DB, "Supralethal Magnesemia With Patient Survival," Obstet Gynecol, 1990, 76(5 Pt 2):984-6.

Chernow B, Smith J, Rainey TG, et al, "Hypomagnesemia: Implications for the Critical Care Specialist," Crit Care Med, 1982, 10(3):193-6.

Ferroggiaro A, Walther JM, and Cairns CB, "High Doses of Magnesium Impair Cardiac Oxidative Metabolism," Acad Emerg Med, 1995, 2:423-9.

Gams JG, "Clinical Significance of Magnesium: A Review," Drug Intell Clin Pharm, 1987, 21(3):240-6.

Lucas MJ, Leveno KJ, and Cunningham FG, "A Comparison of Magnesium Sulfate With Phenytoin for the Prevention of Eclampsia," N Engl J Med, 1995, 333(4):201-5.

Vissers R and Purssell R, "Iatrogenic Intravenous Magnesium Overdose Causing Cardiac Arrest," J Toxicol Clin Toxicol, 1995, 33(5):489.

Worthley LT, "Lithium Toxicity and Refractory Cardiac Arrhythmia Treated With Intravenous Magnesium," Anaesth Intensive Care, 1974, 4:357-60.