Edetate Calcium Disodium

Edetate calcium disodium (CaEDTA) is a heavy metal chelating agent primarily used in veterinary medicine for the treatment of **lead** and **zinc** toxicosis. While succimer (DMSA) is increasingly preferred for lead poisoning in small animals due to its oral formulation and lower nephrotoxicity, CaEDTA remains a critical parenteral antidote, especially in large animals and avian species. > **Critical Clinical Pearl:** It is absolutely vital to ensure the **Calcium Disodium** form of EDTA is used. Administration of Disodium EDTA (Na2EDTA) without calcium can cause rapid, fatal hypocalcemia because it will aggressively chelate the patient's endogenous serum calcium. CaEDTA is highly water-soluble and relies heavily on renal clearance, making adequate hydration and renal monitoring essential during therapy.

กลไกการออกฤทธิ์: CaEDTA works via **competitive chelation**. The calcium ion in the CaEDTA complex has a lower binding affinity than heavy metals. When introduced into the bloodstream, divalent or trivalent heavy metals (such as Pb2+ or Zn2+) displace the calcium: **CaEDTA + Pb2+ → PbEDTA + Ca2+** The resulting heavy metal-EDTA complex is highly stable, water-soluble, and is rapidly excreted by the kidneys into the urine. * Theoretically, 1 gram of CaEDTA binds 620 mg of lead, but in vivo, only about 5 mg of lead is excreted per gram of drug. * It effectively chelates lead and zinc, and to a lesser extent cadmium, copper, iron, and manganese. * It is **ineffective** for mercury, gold, or arsenic poisoning.

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