Magnesium Sulfate

Trade Names:
Epsom Salt
- Granules see care instructions

Trade Names:
Magnesium sulfate
- Injection 4% (0.325 mEq/mL)
- Injection 8% (0.65 mEq/mL)
- Injection 12.5% (1 mEq/mL)
- Injection 50% (4 mEq/mL)

Pharmacology

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Magnesium has CNS depressant effect; prevents/controls seizures by blocking neuromuscular transmission and decreasing amount of acetylcholine liberated at end plate by motor nerve impulse. Orally it attracts/retains water in intestinal lumen, thereby increasing intraluminal pressure and inducing urge to defecate.

Indications and Usage

Seizure prevention and control in severe preeclampsia or eclampsia without deleterious CNS depression in mother, fetus, or newborn; replacement therapy in magnesium deficiency, especially in acute hypomagnesemia accompanied by signs of tetany similar to those observed in hypocalcemia; corrects or prevents hypomagnesemia by addition to total parenteral nutrition admixture.

Unlabeled Uses

Control of hypertension, encephalopathy, and convulsions in children with acute nephritis; inhibition of premature labor; treatment of life-threatening ventricular arrhythmias; prevention and treatment of nutritional magnesium deficiency; laxative (oral).

Contraindications

Toxemia of pregnancy during 2 h preceding delivery; MI; myocardial damage; heartblock.

Dosage and Administration

IM/IV 10 to 14 g of magnesium sulfate (as a combination of IM and IV administration) appropriately diluted.

TPN Maintenance dose ranges from 8 to 24 mEq (1 to 3 g) daily.

TPN Maintenance dose ranges from 2 to 10 mEq (0.25 to 1.25 g) daily.

Usually 1-time dose.

PO 10 to 15 g.

PO 5 to 10 g.

IM Usual dose is 1 g, equivalent to 8.12 mEq magnesium (2 mL of 50% solution) injected every 6 h for 4 doses, equivalent to a total of 32.5 mEq of magnesium per 24 h.

As much as 250 mg (approximately 2 mEq) per kg (0.5 mL of the 50% solution) may be given within a period of 4 h if necessary. Alternatively, 5 g (approximately 40 mEq) can be added to 1 L of dextrose 5% injection or sodium chloride 0.9% injection, for slow IV infusion over a 3-h period. Use caution so as not to exceed the renal excretion capacity.

IM/IV 1 g.

General Advice

• Injection
• For IM or IV administration only. Not for intradermal, subcutaneous, or intra-arterial administration.
• Fifty percent solution may be administered undiluted to adults if given by deep IM injection. Rotate injection sites to reduce tissue irritation.
• Fifty percent solution must be diluted, with sodium chloride 0.9% injection or dextrose 5% injection, to a concentration of 20% or less before IV administration or IM administration in infants and children.
• When administering via IV route, use infusion pump. Deliver in separate line and do not mix with other IV drugs unless compatibility has been established.
• Do not administer if particulate matter, cloudiness, or discoloration noted.
• Discard any unused solution.

Storage/Stability

Store granules and injection at ambient room temperature (59° to 86°F).

Drug Interactions

Administer magnesium sulfate with extreme caution because serious changes in cardiac conduction, which can result in heart block, may occur if administration of calcium is required to treat magnesium toxicity.

Possible additive CNS depressant effects.

Potentiation of neuromuscular blockade.

Decreased absorption of nitrofurantoin (oral magnesium).

Reduced penicillamine effects (oral magnesium).

Decreased absorption of tetracyclines (oral magnesium).

Incompatibility

Alcohol (in high concentrations), alkali carbonates and bicarbonates, alkali hydroxides, arsenates, barium, calcium, clindamycin phosphate, heavy metals, hydrocortisone sodium succinate, phosphates, polymyxin B sulfate, procaine hydrochloride, salicylates, streptomycin, strontium, tartrates, tetracycline, tobramycin.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Cardiac depression; circulatory collapse; hypotension; cardiac arrest.

CNS

CNS depression; depressed reflexes; muscle weakness; flaccid paralysis.

Metabolic

Hypocalcemia.

Respiratory

Respiratory paralysis.

Miscellaneous

Flushing; sweating; hypothermia.

Precautions

Pregnancy

Category A .

Lactation

Excreted in breast milk during parenteral use.

Renal Function

Use with caution; renal function impairment may lead to magnesium intoxication.

Eclampsia

Use IV form only for immediate control of life-threatening convulsions.

Overdosage

Symptoms

Sweating, flushing, thirst, decreased deep tendon reflexes, weakness.

Sedation, loss of deep tendon reflexes, hypothermia, hypotension, heart block, respiratory paralysis.

Patient Information

• Injection
• Advise patient that medication will be prepared and administered by a health care professional in a hospital setting.

• Oral
• Advise patient to mix granules in at least a half-glass of water before swallowing and to follow with full glass of water. Advise patient to mix with ice chips or flavor with lemon or orange juice to make more palatable.
• Educate patient regarding other measures that may help prevent constipation (eg, dietary fiber, adequate fluid intake, regular exercise).
• Caution patient that drug is for short-term laxative use only and that prolonged use can lead to dehydration and electrolyte imbalance.
• Advise patient to discontinue use and notify health care provider of the following: unrelieved constipation, rectal bleeding, symptoms of electrolyte imbalance (eg, muscle cramps or pain, weakness, dizziness).

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