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Ca-DTPA/Zn-DTPA
(Diethylentriamene pentaacetate)

Indications and Usage
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Indications and Usage

FDA Q and A about DPTA (current as of 1/9/2015)
Initial approval announcement (8/11/2004)
See drug labels for most complete prescribing and safety information; text below provides abstracted information
- From FDA
  - Zn-DTPA (PDF - 106 KB)
  - Ca-DTPA (PDF - 121 KB)
- From drug manufacturer: Hameln
  - Zn-DTPA (PDF - 291 KB)
  - Ca-DTPA (PDF - 309 KB)
According to FDA labeling, the chelating agents Ca-DTPA (FDA drug label, PDF - 121 KB) and Zn-DTPA (FDA drug label, PDF - 106 KB), salts of diethylentriamene pentaacetate (DTPA), are approved for the elimination of known or suspected internal contamination with the transuranic (Z > 92) metals 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 with DTPA can be found on the FDA Web pages.
  - Q and A about DTPA (1/9/2015)
  - Initial approval announcement (8/11/2004)
Use and Timing of DTPA
- See details quoted below from FDA information about DTPA
  - “Ca-DTPA and Zn-DTPA should not be administered simultaneously.
  - FDA recommends that, if both products are available, Ca-DTPA be given as the first dose.
    - If additional treatment is needed, treatment should be switched to Zn-DTPA. This treatment sequence is recommended because Ca-DTPA is more effective than Zn-DTPA during the first 24 hours after internal contamination.
    - After the initial 24 hours, Zn-DTPA and Ca-DTPA are similarly effective, but Ca-DTPA causes more loss of essential metals, such as zinc, from the body. Therefore, Zn-DTPA is preferred for maintenance therapy.
    - If Ca-DTPA is not available or treatment cannot be started within the first 24 hours after contamination, treatment should begin with Zn-DTPA.
    - If Zn-DTPA is not available, Ca-DTPA can be given for continued treatment, along with vitamin or mineral supplements that contain zinc.
  - Ca-DTPA and Zn-DTPA can be administered by nebulizer or directly into the blood stream (i.e. intravenously).
    - If the route of internal contamination is through inhalation alone, then nebulized chelation therapy will suffice.
    - If the routes of contamination are multiple (e.g., inhalation and through wounds), then intravenous chelation therapy is preferred.
  - The duration of treatment is dictated by the level of internal contamination and the individual’s response to therapy.
    - Levels of internal contamination should be ascertained weekly during chelation therapy to determine when to terminate treatment.
  - Zn-DTPA is the preferred treatment for the pregnant woman with internal contamination.
    - According to the Ca-DTPA FDA drug label: "Based on animal data, Ca-DTPA may cause fetal harm. Chelation treatment of pregnant women should begin and continue with Zn-DTPA. If Zn-DTPA is not available, Ca-DTPA should be used."
  - In most cases of contamination with transuranium elements, it is unlikely that immediate illness would occur.
  - In order to reduce the risks of future biological effects, Ca-DTPA or Zn-DTPA should be taken as soon as possible after internal contamination, following or concurrent with distancing the individual from the radioactive source and appropriate external decontamination.
  - However, even when treatment cannot be started right away, individuals should be given Ca-DTPA or Zn-DTPA as soon as the products are available.
  - Treatment with Ca-DTPA or Zn-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.
  - See drug labels for discussion of issues related to use in pregnancy.
- 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).
  - Consult experts if treatment is needed in children < 2 years.
  - Safety and efficacy of nebulized route of administration has not been established in the pediatric population
- DTPA dose should not be fractionated. It should only be given as a single dose, once per day.
- The same dose and dose schedule are 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
  - 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.
  - Potential toxicity must be assessed during treatment. (See drug labels for Ca-DTPA and Zn-DTPA.
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).
Potential side effects of DTPA from FDA information quoted below.
- “The main side effect of Ca-DTPA is loss of certain essential nutritional metals, such as zinc, from the body.
- Zinc can be replaced by taking oral zinc supplements.
- Although Zn-DTPA may also decrease the levels of certain nutritional metals, the effect (which can be countered by taking mineral supplements) is less than with Ca-DTPA.
- Chelation therapy administered by nebulized inhalation may cause breathing difficulties in some individuals.
- In addition, Ca-DTPA should be used with caution in patients suffering from a severe form of a disease called hemochromatosis.”
- See drug label for information about pregnancy and breast feeding.