The principal hazard in parenteral magnesium therapy is the production of abnormally high levels of magnesium in the plasma. The most immediate danger to life is respiratory depression. A preparation of Calcium, such as the gluconate or gluceptate, should be at hand for intravenous administration as an antidote.
Magnesium Sulfate Injection can cause fetal harm when administered intravenously by a continuous infusion for longer than 24 hours before delivery, the possibility of the baby's showing signs of neuromuscular or respiratory depression of the newborn should be considered, since fetal toxicity can occur. A baby with hypermagnesemia may require resuscitation and assisted ventilation. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug the patient should be appraised of the potential hazard to the fetus.