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For further information, see CMDT Part 21-14: Hypermagnesemia
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Almost always the result of advanced stages of chronic kidney disease (CKD) and impaired magnesium excretion
Antacids and laxatives are underrecognized sources of magnesium
Pregnant patients may have severe hypermagnesemia from intravenous magnesium therapy for preeclampsia and eclampsia
Magnesium replacement should be done cautiously in patients with CKD, and dose reductions up to 75% may be necessary to avoid hypermagnesemia
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Muscle weakness
Decreased deep tendon reflexes
Mental obtundation
Confusion
Weakness, even flaccid paralysis
Ileus, urinary retention, hypotension
In severe cases, respiratory muscle paralysis or cardiac arrest
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Serum magnesium is elevated
In the common setting of CKD, elevated blood urea nitrogen, serum creatinine, phosphate, and uric acid; serum K+ may be elevated
Serum Ca2+ is often low
ECG may show increased PR interval, broadened QRS complexes, and peaked T waves, probably related to associated hyperkalemia
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Exogenous sources of magnesium should be discontinued
Calcium antagonizes Mg2+ and may be given intravenously as calcium chloride, 500 mg or more at a rate of 100 mg (4.1 mmol)/min
Hemodialysis or peritoneal dialysis may be necessary
Long-term use of magnesium hydroxide and magnesium sulfate should be avoided in patients with advanced stages of CKD