Magnesium homeostasis following chemotherapy with cisplatin: a prospective study.

Retrospective studies suggest that cisplatin chemotherapy regularly leads to hypomagnesemia and occasionally hypocalcemia. The hypomagnesemia has been attributed to renal magnesium wasting. We examined prospectively the incidence of hypomagnesemia, magnesuria, and hypocalcemia in 17 patients receiving chemotherapy with cisplatin. Hypomagnesemia was found in 53% to 88% of patients, depending on the definition of hypomagnesemia. All displayed inappropriate renal excretion of magnesium. Hypocalcemia occurred in one of the 17 prospectively studied patients (5.8%) and in three additional retrospective patients. Hypocalcemic patients demonstrated lower serum magnesium values, higher fractional magnesium excretion, and evidence for reduced intestinal magnesium absorption. We conclude that hypomagnesemia, renal magnesium wasting, and hypocalcemia occur frequently among patients receiving cisplatin. Hypocalcemia occurs in those patients who have the severest renal magnesium wasting, the severest hypomagnesemia, and inadequate intestinal magnesium absorption.