Comparison of two heavy metal chelators for treatment of lead toxicosis in cockatiels

OBJECTIVE: To compare efficacy and safety of meso-2,3-dimercaptosuccinic acid (DMSA) and Ca EDTA for treatment of experimentally induced lead toxicosis in cockatiels (Nymphicus hollandicus). ANIMALS: 137 (69 females, 68 males) healthy cockatiels between 6 months and 8 years old. PROCEDURE: Lead toxicosis was induced by placing lead shot in the gastrointestinal tract. Treatment with Ca EDTA (40 mg/kg of body weight, IM, q 12 h), DMSA (40 or 80 mg/kg, PO, q 12 h), and sodium sulfate salts (SSS; 0.5 mg/kg, PO, q 48 h) was initiated 4 days after induction of lead toxicosis. Blood lead concentrations were determined, using atomic absorption spectrophotometry. Number of birds surviving and blood lead concentrations were compared among groups. RESULTS: In Phase II of the study, administration of DMSA and Ca EDTA significantly decreased blood lead concentrations when used alone or in combination in birds with lead toxicosis. Addition of SSS did not result in further decreases in lead concentrations. Eight of 12 (66.7%) birds without lead toxicosis given 80 mg of DMSA/kg did not survive to the end of the study. Lesions related to treatment with chelating agents were not detected during necropsy. CONCLUSIONS AND CLINICAL RELEVANCE: DMSA and Ca EDTA are effective chelating agents in cockatiels. Because DMSA is administered orally, it may be easier than other chelating agents for bird owners to administer at home. However, the narrow margin of safety of DMSA indicates that this agent should be used with caution.