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 lead in the urine, followed by intravenous and oral PCA. These three agents also had a very satisfactory effect on the output δ-aminolaevulinic acid (ALA) in urine. Oral Ca-EDTA was found to be greatly inferior in both these respects.
In order to study the absorption of the agents and the renal excretion of the formed lead complexes, the urine was collected quantitatively and fractionated in consecutive 4-hour periods, after which the lead excretion during each period was determined. It was found that 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-lead complexes is discussed and indications were found of resorption of the Ca-EDTA-lead complex but not of the PCA-lead complex. The renal excretion of the different ligand-lead complexes was very effective and reached its maximal level within four hours. However, in some subjects excretion of the Ca-EDTA-lead complex showed some delay. An investigation, in four subjects, of a blocking effect of probenecid on the renal excretion of PCA and/or PCA-lead complexes gave no conclusive results. It is concluded that oral PCA is satisfactory in most cases of lead poisoning. However, 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-lead complexes from the gastro-intestinal tract.
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