Magnesium Dosing Information for Health Care Workers

Indications, Dosing

  • bowel preparation
  • cardiac glycoside-induced arrhythmias
  • cardiopulmonary resuscitation†
  • constipation
  • digitoxin toxicity
  • digoxin toxicity
  • dyspepsia
  • eclampsia
  • hypertension
  • hypomagnesemia
  • nutritional supplementation
  • premature labor†
  • seizure prophylaxis†
  • status asthmaticus†
  • torsade de pointes
  • ventricular fibrillation†
  • ventricular tachycardia†

NOTE: One (1) gram of the various magnesium salts contain the following amounts of elemental magnesium:

  • magnesium chloride: 120 mg (9.8 mEq) elemental magnesium.
  • magnesium gluconate: 54 mg (4.4 mEq) elemental magnesium.
  • magnesium lactate: 120 mg (9.8 mEq) elemental magnesium.
  • magnesium oxide: 603 mg (49.6 mEq) elemental magnesium.
  • magnesium sulfate: 99 mg (8.1 mEq) elemental magnesium.

Oral administration

Magnesium sulfate crystals: Dissolve in a full glass of water prior to administration; lemon-flavored carbonated beverages may be used to mask the bitter taste. Administer on an empty stomach for a more rapid effect. Follow each dose with a full glass of water to prevent dehydration. Do not administer at bedtime or late in the evening.

  • Oral solutions: Mix with water and administer on an empty stomach.
  • Oral tablets or capsules: Take with a full glass of water.

Parenteral administration

  • Magnesium sulfate is administered intramuscularly or intravenously.
  • Visually inspect parenteral products for particulate matter and discoloration prior to administration whenever solution and container permit.

Intramuscular injection (magnesium sulfate):

  • For adults, concentrations of 250 mg/ml (25%) or 500 mg/ml (50%) are generally used. For infants and children, concentrations should not exceed 200 mg/ml (20%).
  • Inject into a large muscle mass, preferably into a gluteal site. Aspirate prior to injection to avoid injection into a blood vessel.

Intravenous injection (magnesium sulfate):

  • Concentration should generally not exceed 200 mg/ml (20%).
  • Inject over >= 10 minutes at a rate not to exceed 150 mg/minute.

Intermittent IV infusion (magnesium sulfate):

  • Dilute to a maximum concentration of 100 mg/ml.
  • Infuse IV over 2—4 hours. Infusion rate should not exceed 150 mg/minute or 125 mg/kg/hr. An infusion rate of <= 2g/hour or less decreases the risk of hypotension. Higher infusion rates of up to 4 g/hour may be used in emergencies (obstetrics, seizures, etc.)

For the treatment of hypomagnesemia:

NOTE: Serum magnesium concentrations do not accurately predict cellular magnesium stores.
Oral dosage (magnesium sulfate):
Adults: 3 g PO every 6 hours for 4 doses.
Oral dosage (magnesium chloride, magnesium gluconate, magnesium lactate, magnesium oxide, or magnesium sulfate):
Children: 10—20 mg elemental magnesium/kg/dose PO four times per day.
Parenteral dosage (magnesium sulfate):
Adults: 1—2 g IV/IM (or 15—30 mg/kg lean body weight) every 6 hours for 24 hours. Use the higher end of the dosage range for serum Mg concentrations < 1.2 mg/dl. For extreme hypomagnesemia, 8—12 g/day IV in divided doses have been used. After the first 24 hours, dosages of approximately 60 mg/kg/day may be given in divided doses or as a continuous infusion for the next 2—5 days.
Children: 25—50 mg/kg (0.2—0.4 mEq/kg) IV/IM every 4—6 hours for 3—4 doses. Maximum single dose is 2000 mg (16 mEq). May repeat if hypomagnesemia persists.
Neonates: 25—50 mg/kg (0.2—0.4 mEq/kg) IV (not IM) every 8—12 hours for 2—3 doses.

For nutritional supplementation:

•The recommended dietary allowance (RDA) of magnesium for nutritional supplementation in healthy individuals:
NOTE: Use dosage based on age for lactating females.
Oral dosage expressed in elemental magnesium:
Adult females during pregnancy: 350—360 mg PO per day.
Adult females >= 31 years of age: 320 mg PO per day.
Adult females up to 30 years of age: 310 mg PO per day.
Adult males >= 31 years of age: 420 mg PO per day.
Adult males up to 30 years of age: 400 mg PO per day.
Adolescent females during pregnancy: 400 mg PO per day.
Adolescent females 14—18 years of age: 360 mg PO per day.
Adolescent males 14-18 years of age: 410 mg PO per day.
Children 9—13 years of age: 240 mg PO per day.
Children 4—8 years of age: 130 mg PO per day.
Children 1—3 years of age: 80 mg PO per day.
Infants 6—12 months of age: 75 mg PO per day based on adequate intake (AI); RDA has not been established.
Neonates and infants < 6 months of age: 30 mg PO per day based on adequate intake (AI); RDA has not been established.
•to prevent hypomagnesemia in patients receiving total parenteral nutrition:
Intravenous dosage as magnesium sulfate:
Adults: 16—24 mEq IV per day admixed with parenteral nutrition, depending upon renal function. Undialyzed patients with renal failure generally require 0—8 mEq of magnesium sulfate.
Children and infants: 0.25—1.25 g (2—10 mEq ) IV per day admixed with parenteral nutrition.

For the management of seizures and/or hypertension:

For the treatment of seizures associated with severe toxemia of pregnancy (e.g., eclampsia):Intramuscular or Intravenous dosage (magnesium sulfate):

Adults: The manufacturer recommends an initial IM dose of 1—2 g in 25% or 50% solution, followed by 1 g IM every 30 minutes until seizures abate. Alternatively, an initial dose of 4 g administered by IV infusion as a 25—50% solution has been used. In addition to this initial IV dose, 4—5 g may be given IM into each buttock, followed by IM doses of 4—5 g into alternate buttocks at 4-hour intervals as needed, depending on the patient’s response and the absence of signs of magnesium toxicity. It has also been suggested that doses of 1—3 g/hour given by constant IV infusion via a controlled infusion pump device be administered after the initial IV dose. Another suggested regimen includes an initial dosage of 8—15 g depending on the weight of the patient (i.e., 8 g for a 45-kg patient to 15 g for a 90-kg patient); 4 g is given IV and the remainder of the initial dose is given IM using the undiluted 50% magnesium sulfate injection. The dosage for the next 24 hours should be based on the serum concentration and urinary excretion of magnesium following the initial dose. Subsequent doses should be sufficient to replace the magnesium excreted in the urine and will be about 65% of the initial dose administered IM at 6-hour intervals. The daily maximum dosage should not exceed 30—40 grams/day. In the presence of severe renal insufficiency, frequent serum magnesium concentrations must be obtained and the maximum dosage of magnesium sulfate is 20 g per 48 hours.
For seizure prophylaxis† in women with pregnancy-induced hypertension (preeclampsia):
Intramuscular or intravenous dosage (magnesium sulfate):
Adults: A randomized study compared phenytoin with magnesium sulfate to prevent seizures in women with pregnancy-induced hypertension. Magnesium sulfate was found to be superior to phenytoin. In this study, magnesium sulfate was dosed as follows: 10 g IM followed by 5 g IM every four hours unless patellar reflex was not present, respirations were fewer than 12/minute, or urine output was less than 100 ml during the preceding 4 hours.
If preeclampsia was severe, an initial dose of 4 g IV was given prior to the IM doses. Seizures occurred in 0/1049 women given magnesium and in 10/1089 women given phenytoin.994

Alternatively, initial dose of 4—6 g infused IV over 20—30 minutes as a loading dose, followed by maintenance IV infusions of 1—3 g/hour, delivered via controlled infusion pump device. Deep tendon reflexes, respirations, urinary output, and serum magnesium concentrations should be observed. Average magnesium concentrations associated with prevention of convulsions are 4—7 mg/dl in clinical studies.

For the treatment of hypertension, encephalopathy, and seizures associated with acute nephritis in children:
Intramuscular dosage (magnesium sulfate):
Children: 20—40 mg/kg (0.1—0.2 ml/kg) IM as a 20% solution can be administered as needed to control seizures. Doses as high as 100 mg/kg IM (0.2 ml/kg) of a 50% solution have been administered every 4—6 hours.
Intravenous dosage (magnesium sulfate):
Children: 20—100 mg/kg IV as a 20% solution can be administered every 4—6 hours, as needed. When symptoms are severe, doses of 100—200 mg/kg IV as a 1—3% solution can be administered over 1 hour with half of the dose administered over the first 15—20 minutes. Blood pressure should be closely monitored.

For the management of seizures associated with epilepsy, glomerulonephritis, or hypothyroidism, particularly when hypomagnesemia is present:

Parenteral dosage (magnesium sulfate):
Adults: 1 g IM or IV as a single dose.

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