依地酸鈣鈉 (CaEDTA)
依地酸鈣鈉 (CaEDTA) 是一種重金屬螯合劑，在獸醫學中主要用於治療**鉛**和**鋅**中毒。雖然在小動物鉛中毒的治療中，口服的二巰基丁二酸 (Succimer/DMSA) 因腎毒性較低而越來越受歡迎，但 CaEDTA 仍是大型動物和鳥類重要的注射型解毒劑。 > **重要臨床提示：** 絕對必須確保使用的是**鈣鈉 (Calcium Disodium)** 形式的 EDTA。若錯誤使用不含鈣的依地酸二鈉 (Na2EDTA)，會強烈螯合病患體內的血清鈣，導致迅速且致命的低血鈣症。 CaEDTA 具高度水溶性，且極度依賴腎臟清除，因此在治療期間維持充足的水分和監測腎功能至關重要。
作用機制: 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.
各物種劑量
- Lead poisoning (Psittacines) · 35 mg/kg IM twice daily for 5-7 days. · IM · q12h · 5-7 days · After initial therapy, may give orally until all lead fragments are dissolved and/or passed from GI tract.
- Lead poisoning (Raptors/Falcons) · 100 mg/kg q12h for 5-25 consecutive days. (25% CaEDTA given undiluted IM) · IM · q12h · 5-25 days · Treated if blood lead was >65 micrograms/dL for 5 day courses, until blood lead was <20 micrograms/dL.
- Lead or zinc poisoning · 30-35 mg/kg IM q12h x 3-5 days, off 3-5 days, may repeat and/or use another chelator. · IM · q12h · 3-5 days · Maintain hydration. Do not give orally. Can be used IV short term (48 hrs) at 20-35 mg/kg diluted in saline.
- Lead poisoning · 75 mg/kg IV slowly in D5W or saline daily for 4-5 days (may divide daily dose into 2-3 administrations per day). · IV · q24h or divided q8-12h · 4-5 days · Stop therapy for 2 days and repeat for another 4-5 days. Give adequate supportive and nutritional therapy.
- Lead poisoning · 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. · SC · divided q6h · 5 days · Be sure there is no lead in GI tract before using.
- Lead poisoning · 25 mg/kg SC four times daily for 5 days. Give as 1% solution in D5W. · SC · q6h · 5 days · Provide a 5-7 day rest period between courses of treatment to minimize potential for nephrotoxicity.
給藥途徑
禁忌症
- Patients with anuria
- Oral (PO) administration in the presence of lead in the GI tract (enhances absorption)
不良反應
- Renal toxicity (renal tubular necrosis)
- Depression (dogs)
- Vomiting
- Diarrhea
- Zinc deficiency (with chronic therapy)
- Pain at IM injection site
藥物相互作用
- Glucocorticoids · May enhance the renal toxicity of CaEDTA
- Insulin (NPH, PZI) · Concurrent administration will decrease the sustained action of the insulin preparation due to zinc chelation
- Nephrotoxic drugs (e.g., aminoglycosides, amphotericin B) · Increased risk of nephrotoxicity; use with extreme caution
監測
- 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
過量
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.
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