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Ca-DTPA/Zn-DTPA
(Diethylentriamene pentaacetate)



Indications and Usage


  • According to official FDA labeling, the chelating agents Ca (PDF - 121 KB) and Zn (PDF - 106 KB) salts of diethylentriamene pentaacetate (DTPA) are approved for the elimination of known or suspected internal contamination with the transuranic metals (Z > 92) plutonium, americium, and curium.
    • DTPA should not be used to chelate internal contamination with uranium or neptunium.
    • DTPA compounds are most effective if the metals to chelate are in soluble form.
    • Information about clinical decorporation of other elements with DTPA can be found on the FDA Web site.
  • Timing of DTPA
    • In the first 24 hours after internal contamination, Ca-DTPA is 10 times more effective at chelating transuranic elements than is Zn-DTPA.
    • After 24 hours, Ca-DTPA and Zn-DTPA are equally effective in chelating transuranic elements.
    • FDA recommends using Ca-DTPA instead of Zn-DTPA, if both are available, when chelating in the first 24 hours after internal contamination.
    • The less toxic Zn-DTPA is preferred after the first 24 hours.
    • Ca-DTPA or Zn-DTPA should be administered as soon as possible after internal contamination, while also
      • Distancing the individual from the radioactive source and
      • Performing appropriate external decontamination
    • Even when treatment cannot be started right away, individuals should be given DTPA as soon as the products are available.
    • In most cases of internal contamination with transuranic elements, it is unlikely that immediate illness from the metals themselves would occur. Early onset of ARS, however, could occur.
    • Treatment with DTPA is still effective even after time has elapsed since contamination, but effectiveness decreases once these elements are trapped in the bones.
  • IV Dosing
    • Healthy, non-pregnant adults with normal bone marrow and renal function:
      • 1 g in 5 cc 5% dextrose in water (D5W) or 0.9% sodium chloride (normal saline, NS) slow IV push over 3-4 minutes OR
      • 1 g in 100-250 cc D5W or NS as an infusion over 30 minutes
    • Pregnant women:
      • Zn-DTPA should be used exclusively, if available.
      • Otherwise, use Ca-DTPA as a single-dose therapy and a multivitamin supplement that contains zinc. The same dose and dose schedule is used for Zn-DTPA as for Ca-DTPA.
    • Children (<12 years old):
      • 14 mg DTPA/kg body weight/day in 5 cc D5W or NS slow IV push over 3-4 minutes (not to exceed 1 g/day).
    • DTPA dose should not be fractionated (i.e., it should only be given as a single dose, once per day)
    • The same dose and dose schedule is used for Zn-DTPA as for Ca-DTPA. Zn-DTPA may be administered for extended periods (weeks to months) in most cases without toxic effects.
    • The duration of DTPA therapy depends on
      • The amount of internal radioactive contamination received
      • Each individual's response to therapy, i.e., rate of excretion of the metal. Excretion must be measured clinically to titrate the effectiveness of the chelation therapy.
  • Nebulizer dosing
    • 1 g in 1:1 dilution with sterile water or NS, inhaled over 15-20 minutes
    • FDA recommends nebulized Zn-DTPA for adults whose internal contamination is only by inhalation. The inhaled Zn-DTPA may cause cough or wheezing in asthmatics.
      • The safety and efficacy of the nebulized route of administration has not been established in the pediatric population for Zn-DTPA.
  • Wound irrigation fluid dosing
    • 1 g Ca- or Zn-DTPA and 10 cc 2% lidocaine in 100 cc 5% D5W or NS
    • Irrigation can be accompanied by IV or inhaled DTPA.
    • The amount of DTPA absorbed by wound tissues cannot be measured.
    • Avoid overdosing with DTPA and/or 2% lidocaine.
  • Precautions
    • Since radioactive materials chelated to DTPA are excreted in urine, DTPA must be used carefully in people with diminished renal function.
    • The safety and effectiveness of the intramuscular route of Ca-DTPA or Zn-DTPA administration have not been established.
    • Toxicity is due to chelation of essential metals, such as Zn and Mn.
      • Toxicity includes nausea, vomiting, chills, diarrhea, fever, pruritus, and muscle cramps.
    • Ca-DTPA should be used with caution in patients with hemochromatosis (a genetic disease that causes the body to absorb too much iron from the diet).

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References

  1. Management of Persons Contaminated with Radionuclides: Handbook (NCRP Report No. 161, Vol. I), National Council on Radiation Protection and Measurements, Bethesda, MD, 2008, Decorporation Therapy by Drug (pp. 191-198). [Note: NCRP 161 supersedes NCRP 65.]
 

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