Urinary excretion of essential metals following intravenous calcium disodium edetate: an estimate of free zinc and zinc status in man.

Abstract Ethylenediaminetetraacetic acid (EDTA) is a powerful metal chelating agent used in the treatment of lead poisoning. EDTA also binds strongly to other metals. Thus, following intravenous infusion of CaNa 2 EDTA in healthy subjects the urinary excretion of calcium, copper, iron, magnesium and zinc were assessed. CaNa 2 EDTA significantly increased the urinary excretion of all metals except magnesium with greatest increases for iron (×3.8 above baseline) and zinc (×22). In addition, an in vitro dialysis study with a simplified serum showed that zinc (4.1×10 −3 μmol/h) was taken up more rapidly than iron (2.9×10 −3 μmol/h) by EDTA. The degree of binding of iron and zinc by EDTA depends on two factors: namely, the affinity of EDTA for Zn 2+ and Fe 3+ , and the levels of unbound hydrated Zn 2+ and Fe 3+ (`free' ions). Despite differences in the rate of chelation of Zn 2+ and Fe 3+ by EDTA we show that the measurements of (a) circulating free iron, from routine clinical measurements of transferrin bound iron, and (b) the ratio of zinc:iron excreted in urine could provide an estimate of circulating free zinc, and thereby of zinc status, in man. In addition, EDTA treatment should be evaluated for patients with iron overload.