Medical Uses

Magnesium sulfate is used to treat and prevent low blood magnesium (hypomagnesemia) and seizures in women with eclampsia. It is also employed in the treatment of torsades de pointes, severe asthma exacerbations, constipation, and barium poisoning. Magnesium sulfate can be administered by injection into a vein or muscle, as well as orally. It is also used in the form of Epsom salts for mineral baths.

Common Side Effects

Common side effects include low blood pressure, skin flushing, and low blood calcium. Other potential side effects may include vomiting, muscle weakness, and decreased breathing. While there is evidence that its use during pregnancy may harm the baby, the benefits in certain conditions outweigh the risks. Its use during breastfeeding is considered safe. For medical purposes, magnesium sulfate is typically the heptahydrate salt (MgSO₄·7H₂O). The exact mechanism of action is not fully understood, but it is believed to involve suppressing neuronal activity.

Pharmaceutical Formulation

Magnesium sulfate is a common mineral pharmaceutical preparation of magnesium, known as Epsom salt, used both externally and internally. It is highly soluble in water, but its solubility is reduced when mixed with lipids typically found in lotions. Lotions often use emulsions or suspensions to incorporate both oil-soluble and water-soluble ingredients. Therefore, magnesium sulfate in a lotion may not be as readily available to migrate to the skin or be absorbed through it. Studies on absorption can vary based on the carrier medium (water solution vs. oil emulsion/suspension). Temperature and concentration gradients can also influence absorption.

External Uses

Epsom salt is used as bath salts and in isolation tanks. High concentrations in bath water increase the specific gravity, making the body more buoyant. Traditionally, it is also used to prepare foot baths to soothe sore feet. The increased ionic strength helps prevent temporary skin wrinkling caused by prolonged immersion in pure water. Magnesium and sulfate ions are naturally present in some mineral waters, though the claimed health benefits of Epsom salt baths have not been scientifically proven.

Internal Uses

Oral Magnesium Sulfate: Commonly used as a saline laxative or osmotic purgative.

Replacement Therapy: Used to treat hypomagnesemia.

Antiarrhythmic Agent: Effective for treating torsades de pointes in cardiac arrest, according to ECC guidelines, and for managing quinidine-induced arrhythmias.

Bronchodilator: Can be nebulized to reduce symptoms of acute asthma after beta-agonist and anticholinergic agents have been tried. It is often administered intravenously for severe asthma attacks.

Pre-eclampsia and Eclampsia: Helps decrease the risk of pre-eclampsia progressing to eclampsia. IV magnesium sulfate is used to prevent and treat eclampsia-related seizures. It reduces systolic blood pressure without affecting diastolic blood pressure, ensuring fetal blood perfusion remains uncompromised. Compared to diazepam or phenytoin, magnesium sulfate yields better outcomes in treating eclampsia.

Overdose

An overdose of magnesium can cause hypermagnesemia.