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.
- Dosing
- For normal, healthy, non-pregnant adults with normal bone marrow and renal function, the recommended dose of Ca-DTPA is 1 gm in 250 mL normal saline or 5% dextrose in water, IV over 1 hour.
- For pregnant patients, 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.
- No more than one dose of DTPA per day should be used, and the dose should not be fractionated.
- 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.
- Precautions
- Since radioactive materials chelated to DTPA are excreted in urine, DTPA must be used carefully in people with diminished renal function.
- 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.
- 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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Reference Links
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References |
- Marcus, CS. Administration of decorporation drugs to treat internal radionuclide contamination: medical emergency response to radiologic incidents. RSO Magazine, 2004;9(5):9-15. (PDF - 34 KB)
- "Radiation Bioterrorism," Tochner ZA, Lehavi O, Glatstein E, Chapter 207 in Harrison's Principles of Internal Medicine, Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL, eds. 16th Edition, pp 1294-1300, McGraw-Hill, 2005
- Management of Persons Accidentally Contaminated with Radionuclides, National Council on Radiation Protection and Measurements, NCRP Report No. 65, Bethesda, MD, 1980.
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