Treatment of Lead Poisoning: A Comparison between the Effects of Sodium Calciumedetate and Penicillamine Administered Orally and Intravenously

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Abstract
In 16 workers with lead poisoning of varying degrees, a comparison was made between the therapeutic efficacy of sodium calciumedetate (Ca-EDTA) and penicillamine (PCA), administered intravenously and orally. The question of comparable dosages of ligands, forming metal complexes in different ways, is discussed. With the dosages given, intravenous Ca-EDTA promoted the greatest output of Pb in the urine, followed by intravenous and oral PCA. These 3 agents also had a satisfactory effect on the output of S -aminolaevulinic acid (ALA) in urine. Oral Ca-EDTA was greatly inferior in both these respects. To study the absorption of the agents and the renal excretion of the formed Pb complexes, the urine was collected quantitatively and fractionated in consecutive 4-hr, periods, after which the Pb excretion during each period was determined. The oral absorption of PCA was rapid and quantitatively great, whereas the oral absorption of Ca-EDTA was very slow and quantitatively small. The possible resorption of ligand-Pb complexes is discussed and indications were found of resorption of the Ca-EDTA-lead complex but not of the PCA Pb complex. The renal excretion of the different ligand-Pb complexes was very effective and reached its maximal level within 4 hr. In some subjects excretion of the Ca-EDTA-lead complex showed some delay. An investigation, in 4 subjects, of a blocking effect of probenecid on the renal excretion of PCA and/or PCA Pb complexes gave no conclusive results. Oral PCA is satisfactory in most cases of Pb poisoning. In more severe cases intravenous treatment is preferable. Which agent should be chosen, Ca-EDTA or PCA, appears to be unimportant as both are quite satisfactory from the point of view of treatment, but it seems that Ca-EDTA may cause more serious side-effects. Oral Ca-EDTA is quite unsatisfactory and there is good evidence to indicate that the agent causes a resorption of Ca-EDTA Pb complexes from the gastro-intestinal tract.