Can magnesium sulfate be used for a long time? What are the effects of long‑term use?

Magnesium sulfate is a common prescription medication widely used in clinical practice for its cathartic, choleretic, and anticonvulsant properties, as well as for treating gestational hypertension. However, the medical community generally does not recommend it for long-term use. Its therapeutic concentration is very close to its toxic concentration. Prolonged or excessive use can easily lead to the accumulation of magnesium ions in the body, triggering a series of severe adverse reactions and potentially life-threatening conditions. Therefore, its administration must strictly follow medical advice, and patients should never extend the duration of treatment on their own.

Risk of Hypermagnesemia and Neurotoxicity

The most direct consequence of long-term or high-dose use of magnesium sulfate is an abnormally high concentration of magnesium ions in the body, resulting in hypermagnesemia. Excessive magnesium ions inhibit the central nervous system and neuromuscular junctions. Initially, patients may only experience muscle relaxation, delayed responses, lethargy, or fatigue. However, as blood magnesium levels continue to rise, symptoms may progress to the disappearance of knee-jerk reflexes and slurred speech. In severe cases, it can even induce coma, respiratory depression, and respiratory paralysis.

Increased Renal Burden and Induced Cardiotoxicity

Magnesium ions are primarily excreted by the kidneys. Long-term medication places an additional burden on the kidneys and may cause renal tubular damage, with the risks being particularly significant for patients with renal insufficiency. Furthermore, high concentrations of magnesium ions interfere with the normal physiological functions of myocardial cells, leading to weakened myocardial contractility, arrhythmias, and hypotension. In extreme cases, this cardiotoxicity can trigger severe heart block or even cardiac arrest.

Electrolyte Imbalance and Gastrointestinal Discomfort

Long-term use of magnesium sulfate can also disrupt the body's electrolyte balance. It may induce hypocalcemia, affecting calcium absorption and bone mineralization, and some patients may even develop hemolytic anemia. In the digestive system, oral administration of magnesium sulfate can irritate the gastrointestinal tract, causing nausea, vomiting, abdominal pain, and diarrhea. Conversely, continuous long-term use may lead to severe constipation and even paralytic ileus.

Potential Hazards of Long-term Use in Special Populations

For pregnant women, long-term administration (e.g., exceeding 5-7 days) of magnesium sulfate injection carries significant potential risks. Magnesium ions can freely cross the placenta, potentially causing hypocalcemia, decreased muscle tone, respiratory depression, and skeletal developmental abnormalities (such as reduced bone mass and an increased risk of fractures) in the fetus or neonate. Meanwhile, the mother may also face complications such as postpartum hemorrhage, hypothermia, and pulmonary edema. Therefore, the dosage and duration of magnesium sulfate for pregnant women must be strictly controlled.

Principles of Safe Medication and Poisoning First Aid

During the use of magnesium sulfate, patients require close monitoring of vital signs, as well as regular checks of renal function, blood electrolytes, and urine output. If symptoms such as weakened knee-jerk reflexes, slowed respiratory rate, or a significant decrease in urine output occur, the medication should be stopped immediately, and medical attention should be sought. In the event of acute magnesium poisoning, the primary measure is to stop the infusion. Under the guidance of a physician, calcium agents (such as 10% calcium gluconate) should be administered via slow intravenous injection as an antidote, accompanied by symptomatic supportive treatments like oxygen therapy.