Applies to magnesium citrate: oral capsule, oral tablet
Other dosage forms:
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Applies to magnesium citrate: compounding powder, oral capsule, oral liquid, oral tablet
Mild hypermagnesemia is generally well-tolerated. Moderate or severe hypermagnesemia affects the nervous and cardiovascular systems primarily.
Nervous system side effects have included a decrease in tendon reflexes, muscle weakness, mental confusion, sedation, mental depression, areflexia, coma and respiratory paralysis. CNS depression, often presenting as somnolence, may be more likely and more severe in patients with renal dysfunction.
Nervous system side effects from hypermagnesemia result from suppression of neuromuscular transmission in the CNS and at the neuromuscular junction (which can be antagonized by calcium). Clinically, if serum magnesium (Mg) levels increase to 4 to 7 mEq/L, there may be a decrease in tendon reflexes, muscle weakness, and/or mental confusion or sedation. At levels of 5 to 10 mEq/L, the respiratory rate slows and blood pressure falls. At levels of 10 to 15 mEq/L, there is usually profound mental depression, areflexia, coma and respiratory paralysis. Mg also has a curare-like effect at the neuromuscular junction at serum levels above 10 mEq/L. Death is not uncommon when serum Mg levels rise to 15 mEq/L.
The cardiovascular consequences of hypermagnesemia are due to peripheral vasodilation. Hypotension may be observed when serum Mg levels rise to 5 to 10 mEq/L. Hypotension, depressed myocardial conductivity, and bradyarrhythmias may be associated with levels greater than 10 mEq/L. While some patients are inexplicably able to tolerate extraordinarily high Mg levels, there is a significant risk of asystole when levels rise to 25 mEq/L. The risk of cardiotoxicity from hypermagnesemia is increased in the presence of hypocalcemia, hyperkalemia, acidosis, digitalis therapy, and renal insufficiency.
Cardiovascular side effects have included hypotension, depressed myocardial conductivity, asystole, and bradyarrhythmias.
A metabolic concern in the case of acute hypermagnesemia is hypocalcemia. Elevated Mg may cause hypocalcemia due to suppression of the release of parathyroid hormone (PTH) and competition for renal tubular reabsorption between calcium (Ca) and Mg. The latter can lead to decreased Ca reabsorption and hypercalciuria, which aggravates the hypocalcemia produced by decreased release of PTH.
Metabolic side effects have included hypocalcemia. The effects of hypermagnesemia may be worsened by the presence of hypocalcemia, especially in patients with uremia.
Gastrointestinal side effects include nausea when serum Mg levels rise to 4 to 5 mEq/L.
Rare cases of paralytic ileus associated with serum Mg levels greater than 5 mEq/L have been reported.
Gastrointestinal side effects have included nausea, and paralytic ileus (rarely).
Medically reviewed by BestRx Medical Team Last updated on 1/1/2020.
Source: Drugs.com Magnesium Citrate