Intramuscular administration of iron during long-term chelation therapy with 2,3-dimercaptosuccinic acid in a man with severe lead poisoning

Abstract

2,3-Dimercaptosuccinic acid (DMSA) an investigational chelant structurally similar to dimercaptopropanol (BAL), offers the advantage of not depleting iron stores on which basis it would not seem to form a toxic chelate with iron. We report the case of a man with a formidable body burden of lead (Pb) and depleted iron stores who was given iron intramuscularly during a defined period of long-term retreatment with DMSA. Initiation of retreatment with DMSA, 30 mg/kg/day given orally in three divided doses for the first 7 days markedly enhanced Pb diuresis, entailed a pronounced fall in blood Pb and abolished symptoms of Pb poisoning. Continuation of retreatment with two-thirds the initial DMSA dose for an added 15 days maintained blood Pb at sustained low levels. Iron sorbitol administered intramuscularly during this period in individual doses of 100 mg of elemental iron given 3 days apart to a conservative total of 400 mg produced no untoward effects, suggesting that a toxic chelate between iron and DMSA was not formed. Serum ferritin entered the normal range and there was virtually an immediate significant decrease in erythrocyte protoporphyrin. Together with discernible increases in haemoglobin, haematocrit and MCV, this pointed to enhanced iron utilization. Since iron utilization is curtailed by high concentrations of Pb, the immediacy and magnitude of the post-chelation rebound in blood Pb precluded iron administration at any other stage. From these data, DMSA emerges as a uniquely versatile new chelant. Suitable for long-term administration, it permits the simultaneous parenteral administration of iron during dose-related sustained decreases in blood Pb.