Changes in intracellular magnesium concentrations during cisplatin chemotherapy

Magnesium is mainly an intracellular cation, and its availability is not represented reliably by plasma levels. The effects of cisplatin on Mg concentrations in plasma (PMg) and erythrocytes (EMg) were investigated in 22 neoplastic patients. Assays were done before and 1, 2, 4 and 7 days after cisplatin administration; 10 patients were also checked following six courses of chemotherapy. PMg decreased progressively either day by day after a single dose of cisplatin (p < 0.001 on the 7th day) or month by month after cumulative doses (p < 0.05 after two courses and p < 0.001 after six). EMg decreased till the 4th day (p < 0.001), but recovered pretreatment levels on the 7th day; an actual depletion was manifested only after the third course of chemotherapy (p < 0.05) and became more marked after the 6th. These results suggest that, besides renal Mg wasting, Mg metabolism is influenced by cisplatin also at a cellular level. The cisplatin-induced injury on membrane transport systems, where Mg is abundant and plays an important stabilizing role, might induce an early shift of Mg from cells into the blood stream. When repair systems begin to act, Mg is taken up from plasma to recover the normal cellular content. The lack of an actual depletion of Mg body stores till the third course of chemotherapy possibly makes the early Mg supplementation commonly administered before or contemporaneously to cisplatin infusion unnecessary. Oral supplements between the courses might be sufficient to prevent Mg depletion without exposing the patients to the risk of hypermagnesemia in case of cisplatin-induced acute renal failure.