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  1. Pharmacology. Diethylenetriaminepentaacetate (Zn-DTPA and Ca-DTPA) is a chelating agent that is used in exposures to the transuranic elements plutonium, americium, and curium. DTPA is used as a salt of calcium or zinc and forms a chelate that is excreted in the urine. DTPA has a plasma half-life of 20–60 minutes and is distributed in the extracellular space. It has a small amount of protein binding and does not undergo significant metabolism or tissue accumulation. Ca-DTPA resulted in a 10-fold higher rate of elimination of plutonium compared with Zn-DTPA, so this salt is preferred in initial patient management if available.

  2. Indications. Internal contamination with plutonium, americium, or curium. It has also been used for the treatment of internal contamination with californium and berkelium.

  3. Contraindications

    1. Known hypersensitivity to the agent.

    2. DTPA should not be used in uranium or neptunium exposures because it may increase bone deposition of these elements.

    3. Ca-DTPA should not be used in patients with renal failure, nephrotic syndrome, or bone marrow suppression, or in those who are pregnant.

  4. Adverse effects

    1. Nausea, vomiting, and diarrhea.

    2. Fever, chills, myalgias, headache, metallic taste, dermatitis.

    3. Life-threatening side effects are distinctly uncommon, with no serious toxicity in human subjects after 4,500 administrations of Ca-DTPA and 1,000 administrations of Zn-DTPA.

    4. Use in pregnancy. FDA Category D (Ca-DTPA) and Category C (Zn-DTPA); Zn-DTPA may be used in pregnancy, although fetal risks are not completely known (Introduction).

  5. Drug or laboratory interactions

    1. There are no major known drug interactions.

    2. There does not appear to be a decrement of body trace elements associated with the use of DTPA.

  6. Dosage and method of administration

    1. Upon known exposure, usual therapy would involve Ca-DTPA or Zn-DTPA given in a 1-g dose as soon as possible. This may be given IV over 3–5 minutes in an undiluted form or may be diluted in 100–250 mL of normal saline, lactated Ringer's solution, or 5% dextrose in water. Administration time should not exceed 2 hours. Initial dose for pediatric patients is 14 mg/kg, not to exceed 1 g.

    2. It is preferable to give Ca-DTPA for the initial dose because it is more effective than Zn-DTPA during the first 24 hours. After 24 hours, Zn-DTPA and Ca-DTPA are equally effective. If Ca-DTPA is not available or is contraindicated in a patient, the same dose of Zn-DTPA may be substituted. The FDA advises that Zn-DTPA is preferred for maintenance therapy because it is associated with smaller losses of essential minerals.

    3. After the initial dose of Ca-DTPA, repeat doses of 1 g of Ca-DTPA or Zn-DTPA should be based on suspected level of internal contamination. Starting at the time of exposure, collect urine and fecal samples for bioassay to guide further treatment after the initial dose. The doses may be continued (usually 2–3 times per week) until the excretion rate of the transuranic is not increased by chelation administration (duration may vary from days to years). For long-term use, Ca-DTPA should be given with supplemental zinc therapy ...

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