Onset and Duration
Dosage and Administration
Magnesium sulfate reduces striated muscle contractions and blocks peripheral neuromuscular transmission by reducing acetylcholine release at the myoneural junction. In emergency care, magnesium sulfate is used to manage seizures associated with toxemia of pregnancy. Other uses include uterine relaxation (to inhibit contractions of premature labor), as a bronchodilator after beta-agonist and anticholinergic agents have been used, replacement therapy for magnesium deficiency, as a cathartic to reduce the absorption of poisons from the Gl tract, and in the initial therapy for convulsions. Magnesium sulfate is gaining popularity as an initial treatment in the management of various dysrhythmias, particularly torsades de pointes, and dysrhythmias secondary to a tricyclic antidepressant overdose or digitalis toxicity. The drug is also considered as a class Ila agent (probably helpful) for refractory ventricular fibrillation and ventricular tachycardia after administration of lidocaine or bretylium doses.
Seizures of eclampsia (toxemia of pregnancy)
Torsades de pointes
Reduced heart rate
CNS depressant effects may be enhanced if the patient is taking other CNS depressants.
Serious changes in cardiac function may occur with cardiac glycosides.
5 and 10 ml of a 10% solution in prefilled syringe
Pregnancy safety: Magnesium sulfate is administered to treat toxemia of pregnancy. It is recommended that the drug not be administered in the 2 hours before delivery, if possible. IV calcium gluconate or calcium chloride should be available as an antagonist to magnesium if needed. Convulsions may occur up to 48 hr after delivery, necessitating continued therapy. The "cure" for toxemia is delivery of the baby. Magnesium must be used with caution in patients with renal failure, since it is cleared by the kidneys and can reach toxic levels easily in those patients. Prophylactic administration of magnesium sulfate for patients with acute mvocardial infarction should be considered.