What are the toxic reactions of magnesium sulfate?

Under normal circumstances, magnesium sulfate overdose can easily trigger multi-system toxic reactions, mainly including central nervous system depression, neuromuscular junction blockade, cardiovascular abnormalities, gastrointestinal discomfort, and electrolyte disturbances. The specific analysis is as follows:

1. Central nervous system depression: Early symptoms include dizziness, headache, and fatigue. As serum magnesium levels rise, somnolence and confusion may develop. In severe cases, central inhibition intensifies, leading to restlessness, seizures, and ultimately coma.

2. Neuromuscular junction blockade: Excess magnesium ions competitively inhibit calcium ion activity, impairing acetylcholine release at the neuromuscular junction and resulting in muscle weakness. Initial manifestations include limb weakness and diminished tendon reflexes, which may progress to dysphagia and respiratory distress.

3. Cardiovascular abnormalities: Elevated serum magnesium levels can suppress myocardial contractility and dilate peripheral blood vessels, leading initially to hypotension and bradycardia. As the condition progresses, arrhythmias such as atrioventricular block may occur, and severe cases may result in cardiac arrest—particularly with intravenous administration, which carries a higher risk.

4. Gastrointestinal discomfort: These are often early signs of toxicity, including nausea, vomiting, abdominal pain, and bloating, with some patients experiencing diarrhea. These symptoms are related to magnesium ions irritating the gastrointestinal mucosa and accelerating intestinal motility, typically occurring shortly after starting treatment or increasing the dose.

5. Electrolyte disturbances: Magnesium sulfate overdose can easily cause hypocalcemia, manifesting as tetany, perioral numbness, and muscle spasms. It may also be accompanied by electrolyte imbalances associated with hypermagnesemia itself, exacerbating neuro-muscular and cardiovascular toxicity and creating a vicious cycle.

Clinical use of magnesium sulfate must strictly follow medical instructions regarding dosage. Regular monitoring of serum magnesium levels, tendon reflexes, heart rate, and blood pressure is essential during treatment. The medication should be properly stored in daily life to prevent accidental ingestion, especially with children and patients with renal insufficiency requiring particular caution to reduce the risk of toxicity.