In Reply.—We agree with Li Volti et al that the renal side effects described in our article are conceivably dose dependent. However, in a study we just completed, we compared glomerular filtration rate in the same patients just before the regular subcutaneous dose of deferoxamine, then during the day of chelation and for 3 days thereafter the same tendency of decreased glomerular filtration rate was shown. It well may be that in patients with underlying renal problems, such an insult would be detrimental even with the regular dose of deferoxamine.
At present, we believe that the inability to reabsorb sodium and concentrate urine seen in these patients is probably a nonspecific diuretic effect of ferrioxamine, which is known to concentrate to high urinary levels. This effect may be very similar to mannitol diuresis.