Prevention of cyclophosphamide-induced antidiuresis by furosemide infusion

In patients receiving high-dose cyclophosphamide therapy (HDCPT), urinary flow rate, serum sodium concentration, and renal free-water clearance frequently decrease in the 24 hr after drug. High urinary flow rates, which may minimize other cyclophosphamide-related symptoms, are difficult to achieve in the face of the antidiuretic effect. Five patients receiving a total of 30 doses of HDCPT (greater than 50 mg/kg) were studied to assess the effect of continuous furosemide infusion on cyclophosphamide antidiuresis. In two patients receiving various diuretic regimens, only the continuous infusion of furosemide was associated with maintenance of high urinary flow rates and normal serum sodium concentrations. Four patients studied prospectively while receiving HDCPT maintained renal free-water clearance as well as high constant urinary flow rates and normal serum sodium concentrations. Concurrent studies of furosemide disposition revealed that renal excretion of furosemide was unchanged during the continuous infusion and that the diuretic effect was sustained throughout the therapeutic course. The only furosemide-related side effect identified was hypokalemia, which was easily managed with potassium chloride given intravenously.