How increased magnesium intake can be a cause of hypermagnesemia
Magnesium is an active ingredient in multiple laxatives and antacids. Epsom salt is magnesium sulfate. It can be taken as an enema or orally. Epsom salts are a folk remedy for a variety of ailments from abdominal pain (it is an effective cathartic) to cerebral edema (ineffective) to halitosis (unable to find convincing blinded analysis).
One tablespoon of Epsom salt contains approximately 35 g of magnesium sulfate, which is 3.4 g of elemental magnesium.
IV magnesium leads to hypermagnesemia. Magnesium is the most common agent used to treat eclampsia and preeclampsia. Patients are typically loaded with 4 g of IV magnesium sulfate, followed by an infusion of 1 to 2 g/h. This typically produces stable magnesium levels of 6 to 8.5 mg/dL (2.5 to 3.5 mmol/L). Most clinicians do not follow biochemical levels, but screen for toxicity by checking the patellar reflex. Loss of the reflex occurs at magnesium levels above 8.5 mg/dL (3.5 mmol/L). Magnesium for eclampsia and preeclampsia can occasionally cause a solute diuresis.
The intracellular concentration of magnesium is roughly 10 to 20 times as high as the extracellular concentration. Cell lysis due to rhabdomyolysis, infarction, or hemolysis releases intracellular magnesium, causing hypermagnesemia.