Safety and efficacy of meso-2,3-dimercaptosuccinic acid (DMSA) in childrenwith elevated blood lead concentrations

Objective: To evaluate the safety and efficacy of meso-2,3-dimercaptosuccin ic acid in the treatment of children with lead toxicity. Design: This was a n open-label study in 59 children 12-65-months old, with pretreatment whole -blood lead levels of 25-66 mu g/dL, who received 116, 26-28 day courses of oral dimercaptosuccinic acid, while residing either in the Pediatric Clini cal Research Unit of the Johns Hopkins Hospital or in lead-safe housing dur ing the outpatient portion of the study. Results: All, who completed the st udy, showed sharp decreases in blood lead concentration during therapy, but 2-3 weeks following completion of drug therapy, blood lead concentration r ebounded to an average of 58% (23 mu g Pb/dL of whole blood) of their avera ge pretreatment blood lead concentration (40 mu g Pb/dL of whole blood). Th ere were no adverse reactions attributable to dimercaptosuccinic acid; howe ver, 2 of the 59 patients were reexposed to defective lead paint and experi enced sharp increases in blood lead concentration while on therapy. In one instance, the child's blood lead concentration increased from 20 to 90 mu g Pb/dL whole blood in 1 week. Other unexpected events were discussed in the text. Conclusions: Dimercaptosuccinic acid is apparently safe and does mob ilize lead into the urine, but not the essential metals, zinc and copper. R eexposure is always a danger; therefore, all children, while on therapy, sh ould be monitored for their blood lead concentration at weekly intervals du ring and immediately after therapy. No conclusions can be drawn from this s tudy regarding long-term beneficial effects, if any, of this drug on late n eurocognitive outcome.