• Clinical Info

Uses

Prevention and Control of Seizures

Injection mainly used as an anticonvulsant for the prevention and control of seizures in toxemia (preeclampsia or eclampsia) of pregnancy, acute nephritis (in children), and in various other conditions.

Toxemias of Pregnancy

Generally considered the anticonvulsant drug of choice for the prevention and control of seizures in severe preeclampsia or in eclampsia, and appears to be more effective than phenytoin.

Opinions differ regarding the role for prophylactic use in preventing seizures in mild preeclampsia or gestational hypertension†.

Also used in the management of uterine tetany, especially that associated with the use of oxytocic agents.

Acute Nephritis in Children

Has been used to control seizures, encephalopathy, and hypertension associated with acute nephritis in children. However, other agents (e.g., barbiturates, reserpine, hydralazine) should be tried first.

Some clinicians caution not to use parenteral magnesium sulfate to control seizures unless hypomagnesemia has been confirmed, and to monitor serum magnesium concentration when administered.

Reserve IV use for immediate control of life-threatening seizures.

Other Seizure Etiologies

Parenterally, may be useful to control seizures associated with epilepsy, glomerulonephritis, or hypothyroidism, since low plasma concentrations of magnesium may be a contributing cause of seizures in these conditions.

Prevention and Treatment of Hypomagnesemia

Injection is added to total parenteral nutrition admixtures to correct or prevent hypomagnesemia.

Treatment of acute hypomagnesemia associated with clinical conditions including malabsorption syndromes, alcoholism, cirrhosis of the liver, acute pancreatitis, or prolonged IV therapy with magnesium-free fluids.

Especially effective in the treatment of acute hypomagnesemia accompanied by signs of tetany similar to those of hypocalcemia; usually, serum magnesium concentrations are below the lower limits of normal (1.5–2.5 or 3 mEq/L), and serum calcium concentrations are either normal (4.3–5.3 mEq/L) or elevated in such cases.

Preterm Labor

Has been used to inhibit uterine contractions in preterm labor (tocolysis)† and prolong gestation when beneficial.

Previously, the American College of Obstetricians and Gynecologists (ACOG) considered magnesium sulfate a first-line tocolytic agent of choice; currently, ACOG states that there is no clear first-line tocolytic agent.

May be contraindicated by maternal or fetal conditions. (See Contraindications under Cautions.)

Following successful cessation of uterine contractions, oral maintenance therapy with other magnesium salts (e.g., oxide or gluconate) has not been consistently beneficial.

Combination therapy with another tocolytic agent may be more effective than single-agent therapy, but may increase risk of maternal morbidity, and safety and efficacy have not been established; use with caution.

Concurrent use of magnesium sulfate and nifedipine may be particularly risky (e.g., development of severe hypotension and neuromuscular blockade).

Arrhythmias

Used IV successfully for the treatment of life-threatening arrhythmias such as atypical VT† (torsades de pointes).

Considered one of several preferred drugs in the treatment of polymorphic VT suspected of being torsades de pointes† in patients in whom initial attempts at correcting or managing potential precipitating factors (e.g., ischemic cardiac events, electrolyte imbalance, drugs known to prolong the QT interval) have not been successful.

Not recommended in the treatment of cardiac arrest except as an alternative therapy when the arrhythmias are suspected to be caused by hypomagnesemia or when the ECG monitoring shows torsades de pointes.

Drug-induced cardiovascular emergencies or altered vital signs: May consider use in VT associated with tricyclic antidepressant toxicity; however, use may aggravate drug-induced hypotension. Anecdotal evidence suggests that magnesium sulfate also may be an effective treatment in antiarrhythmic drug-induced torsades de pointes even in the absence of magnesium deficiency.

Has been used IV in the management of paroxysmal atrial tachycardia† when other measures have failed and when there is no evidence of myocardial damage.

May consider use in atrial fibrillation with a rapid ventricular response† for rate control.

AMI

Has been administered IV adjunctively to reduce cardiovascular morbidity and mortality (e.g., through reduction in ventricular arrhythmias and/or limitation of infarct size and reperfusion injury) associated with AMI†; however, evidence of benefit is contradictory and the precise role remains unclear.

Routine magnesium prophylaxis in AMI no longer recommended.

Instead, ACC and AHA currently recommend that magnesium in AMI be reserved for patients with documented magnesium and/or potassium deficits, especially in patients receiving diuretics prior to infarction.

ACC/AHA state that it is sound clinical practice to maintain magnesium concentrations >2 mEq/L in patients with AMI.

Recommended by ACC/AHA in AMI for episodes of torsades de pointes-type VT.

Recommended by ACC/AHA for consideration in high-risk patients such as geriatric patients and/or those for whom reperfusion therapy is not suitable.

ACC/AHA state that mortality reduction may be possible with magnesium use in certain high-risk patients with AMI (e.g., geriatric patients, those who are not eligible for reperfusion therapy) if they receive the drug as soon as possible after symptom onset (within 6 hours); however, conflicting evidence and/or divergence of opinion about usefulness/efficacy.

Acute Asthma

Data do not support routine IV magnesium sulfate use in asthma; some experts state that it may be beneficial in some children with severe persistent asthma unresponsive to adequate trials of conventional therapy.

Usefulness in treatment of acute asthmatic attacks† in children is unclear.

May modestly improve pulmonary function and reduce hospital admissions when combined with nebulized β-adrenergic agents and corticosteroids, particularly in patients with severe exacerbations of asthma†.

Barium Poisoning

Administered IV to counteract the intense muscle stimulating effects of barium poisoning.

Also may administer by gastric lavage or oral solution to precipitate and remove unabsorbed barium. (See Dosage under Dosage and Administration.)