Manifestations of magnesium toxicity include a drop in blood pressure, difficulty breathing, and disappearance of the patellar reflex. As serum magnesium rises above 4 mEq per liter, the deep tendon reflexes decrease. As the serum magnesium level approaches 10 mEq per liter, the tendon reflexes disappear and respiratory paralysis may occur [see Warnings and Precautions (5.2)]. Other signs and symptoms of magnesium overdosage include flushing, sweating, hypotension, weakness, hypothermia, circulatory collapse, cardiac and central nervous system depression proceeding to respiratory paralysis, cardiac arrest, and prolongation of PR and QRS intervals. Patients with renal impairment and underlying neuromuscular diseases such as myasthenia gravis may experience magnesium intoxication at lower magnesium concentrations (Magnesium Sulfate in 5% Dextrose Injection is contraindicated in patients with myasthenia gravis).
If patient is experiencing magnesium toxicity, immediately discontinue Magnesium Sulfate in 5% Dextrose Injection. Artificial respiration may be required. Administer an injectable calcium salt to counteract the potential hazards of magnesium toxicity [see Warnings and Precautions (5.2)].
Hypermagnesemia in the newborn (after administration of Magnesium Sulfate in 5% Dextrose Injection to the mother) may require resuscitation and assisted ventilation via endotracheal intubation or intermittent positive pressure ventilation as well as intravenous calcium.