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.
Mechanism: 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+ โ 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.
Dosing by species
- Lead poisoning (Psittacines) ยท 35 mg/kg IM twice daily for 5-7 days. ยท IM ยท q12h ยท 5-7 days ยท After initial therapy, may give orally until all lead fragments are dissolved and/or passed from GI tract.
- Lead poisoning (Raptors/Falcons) ยท 100 mg/kg q12h for 5-25 consecutive days. (25% CaEDTA given undiluted IM) ยท IM ยท q12h ยท 5-25 days ยท Treated if blood lead was >65 micrograms/dL for 5 day courses, until blood lead was <20 micrograms/dL.
- Lead or zinc poisoning ยท 30-35 mg/kg IM q12h x 3-5 days, off 3-5 days, may repeat and/or use another chelator. ยท IM ยท q12h ยท 3-5 days ยท Maintain hydration. Do not give orally. Can be used IV short term (48 hrs) at 20-35 mg/kg diluted in saline.
- Lead poisoning ยท 75 mg/kg IV slowly in D5W or saline daily for 4-5 days (may divide daily dose into 2-3 administrations per day). ยท IV ยท q24h or divided q8-12h ยท 4-5 days ยท Stop therapy for 2 days and repeat for another 4-5 days. Give adequate supportive and nutritional therapy.
- Lead poisoning ยท 100 mg/kg SC divided into 4 daily doses in 5% dextrose for 5 days. May require second course of treatment, particularly if blood lead levels >0.10 ppm. Do not exceed 2 g/day and do not treat for more than 5 consecutive days. ยท SC ยท divided q6h ยท 5 days ยท Be sure there is no lead in GI tract before using.
- Lead poisoning ยท 25 mg/kg SC four times daily for 5 days. Give as 1% solution in D5W. ยท SC ยท q6h ยท 5 days ยท Provide a 5-7 day rest period between courses of treatment to minimize potential for nephrotoxicity.
Routes of administration
Contraindications
- Patients with anuria
- Oral (PO) administration in the presence of lead in the GI tract (enhances absorption)
Adverse effects
- Renal toxicity (renal tubular necrosis)
- Depression (dogs)
- Vomiting
- Diarrhea
- Zinc deficiency (with chronic therapy)
- Pain at IM injection site
Drug interactions
- Glucocorticoids ยท May enhance the renal toxicity of CaEDTA
- Insulin (NPH, PZI) ยท Concurrent administration will decrease the sustained action of the insulin preparation due to zinc chelation
- Nephrotoxic drugs (e.g., aminoglycosides, amphotericin B) ยท Increased risk of nephrotoxicity; use with extreme caution
Monitoring
- Blood lead or zinc levels (serial monitoring)
- Urine d-ALA
- Renal function tests (BUN, Creatinine)
- Urinalyses (monitor for casts/glucose indicating tubular damage)
- Hydration status
- Serum phosphorus and calcium values
- Periodic cardiac rate/rhythm monitoring
Overdose
Doses greater than 12 g/kg are lethal in dogs. Acute toxicity primarily manifests as severe **renal tubular necrosis**. It can also cause profound depression, vomiting, and diarrhea. Treatment of overdose is largely supportive, focusing on maintaining diuresis and managing uremia.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.