Which of the following statement(s) is/are true concerning alterations in serum magnesium?

a. Renal failure is the primary cause of hypermagnesemia

b. Hypomagnesemia may occur during prolonged periods of intravenous fluid replacement

c. Symptoms of hypomagnesemia may mimic symptoms of hypocalcemia

d. Intravenous administration of magnesium sulfate is usually the most efficient method of correction of magnesium deficiency

Renal failure is the primary cause of hypermagnesemia. Because of the kidneys ability to excrete large magnesium loads, hypermagnesemia rarely occurs if renal function remains normal. Because the kidneys are able to conserve magnesium well in states of magnesium depletion, hypomagnesemia rarely occurs from poor intake alone. The combination of low intake and increased gastrointestinal loss may lead to hypomagnesemia. Prolonged periods of intravenous fluid replacement without magnesium replacement and the chronic use of loop diuretics or other medications such as cyclosporine or aminoglycosides can also result in hypomagnesemia. Deficiencies of magnesium may present signs and symptoms similar to hypocalcemia. Hypomagnesemia may be treated by the oral administration of magnesium however large doses frequently leads to diarrhea. Correction of major deficits is therefore best managed by intravenous administration of magnesium sulfate at a dose of 50 to 100 mEq/d.