Changes in serum, erythrocyte, and urinary magnesium after a single dose of cisplatin combination chemotherapy

The changes in serum and erythrocyte Mg concentrations and in renal Mg excretion induced by a single dose of cisplatin (100 mg/mq body surface area) were investigated in 16 patients with lung cancer. Magnesuria increased significantly (P less than 0.001) the day after cisplatin administration, returned to basal levels in the following days, and increased again on the 7th day (P less than 0.05). Magnesaemia decreased gradually and after 7 was significantly lower than before treatment (P less than 0.05). Erythrocyte Mg decreased significantly on days 1 (P less than 0.05) and 2 (P less than 0.001) after cisplatin administration, began to increase on day 4, and recovered to pretreatment values on day 7. These results suggest that, besides the well known damage to tubular function with consequent increase in renal Mg wasting, cisplatin may also interfere with Mg metabolism at cellular and subcellular levels. The activity of the drug on nucleic acids and membrane transport systems, where Mg is abundant and exerts important stabilizing functions, could induce Mg mobilization and increased membrane permeability, with a consequent shift of Mg from cells into the blood stream. This would counterbalance the increase in magnesuria, and magnesaemia would decrease significantly only when intracellular Mg returns to pretreatment levels.