What is the purpose of magnesium sulfate (MgSO4) in medical settings?

Purposes of Magnesium Sulfate in Medical Settings

Magnesium sulfate (MgSO4) has multiple important clinical applications including treatment of pre-eclampsia/eclampsia, management of torsade de pointes arrhythmias, treatment of severe asthma exacerbations, fetal neuroprotection in preterm deliveries, and replacement therapy in magnesium deficiency.

Pre-eclampsia and Eclampsia Management

• Magnesium sulfate is indicated for prevention and control of seizures in pre-eclampsia and eclampsia, respectively 1
• The standard regimen for eclampsia includes:
  • Intravenous loading dose of 4-5g in 250mL of appropriate solution
  • Followed by maintenance of 1-2g/hour by continuous IV infusion 1
• Alternative regimen includes:
  • Initial IV dose of 4-5g followed by IM doses of 4-5g every four hours as needed
  • Therapy continues until paroxysms cease 1
• Serum magnesium level of 6 mg/100mL is considered optimal for seizure control 1
• Magnesium sulfate has been proven superior to other anticonvulsants like diazepam or phenytoin for preventing recurrent seizures in eclamptic patients 2

Cardiac Applications: Torsade de Pointes Management

• Intravenous magnesium sulfate (2g) is recommended as first-line therapy for patients with torsade de pointes and prolonged QT interval 3
• For persistent episodes, repeated infusions of magnesium sulfate 2g may be necessary 3
• The mechanism of action is not fully understood, but magnesium is effective regardless of serum magnesium level 3

Severe Asthma Exacerbations

• Magnesium sulfate causes relaxation of bronchial smooth muscle, providing complementary bronchodilator effects to standard treatments 4
• IV magnesium sulfate should be considered for patients with severe asthma exacerbations that remain severe after 1 hour of intensive conventional treatment 4
• The standard adult dose is 2g administered intravenously over 20 minutes 4
• IV magnesium sulfate improves pulmonary function and reduces hospital admissions, particularly for patients with the most severe exacerbations 4

Fetal Neuroprotection in Preterm Delivery

• Magnesium sulfate is recommended for fetal neuroprotection when preterm delivery is anticipated before 32 weeks' gestation 5
• It significantly reduces the risk of cerebral palsy without increasing mortality 5
• For women with preeclampsia, magnesium sulfate serves dual purposes: prevention of eclamptic seizures and fetal neuroprotection 5
• Continuous maternal administration beyond 5-7 days can cause fetal abnormalities 1

Magnesium Deficiency Treatment

• For mild magnesium deficiency, the usual adult dose is 1g injected IM every six hours for four doses 1
• For severe hypomagnesemia, up to 250mg per kg of body weight may be given IM within a four-hour period 1
• Alternatively, 5g can be added to one liter of appropriate solution for slow IV infusion over a three-hour period 1
• Magnesium sulfate is suitable for replacement therapy in magnesium deficiency, especially in acute hypomagnesemia accompanied by signs of tetany 1

Other Uses

• In total parenteral nutrition (TPN), magnesium sulfate may be added to correct or prevent hypomagnesemia 1
• For counteracting muscle-stimulating effects of barium poisoning, the usual dose is 1-2g given IV 1
• In paroxysmal atrial tachycardia, 3-4g may be administered IV over 30 seconds when simpler measures have failed 1
• For reduction of cerebral edema, 2.5g is given IV 1

Monitoring and Safety Considerations

• Clinical effects and toxicity are linked to plasma concentration:
  • Loss of patellar reflex occurs at 3.5-5 mmol/L (first warning sign)
  • Respiratory paralysis occurs at 5-6.5 mmol/L
  • Cardiac conduction alterations occur at >7.5 mmol/L
  • Cardiac arrest can occur at >12.5 mmol/L 6
• Monitoring should include deep tendon reflexes, respiratory rate, urine output, and serum concentrations 6
• In patients with severe renal insufficiency, maximum dosage should not exceed 20g/48 hours with frequent serum magnesium monitoring 1

Dosing Considerations

• Solutions for IV infusion must be diluted to a concentration of 20% or less prior to administration 1
• Total daily dose should not exceed 30-40g in a 24-hour period 1
• Dosing should be adjusted in patients with renal impairment 1
• For neuroprotection, evidence suggests lower doses (4-10.5g) may provide better protection while avoiding toxicity 7