This section will introduce diethylene triamine pentaacetic acid, or DTPA, and discuss its indications, administration, adverse effects, and special considerations. Afterwards, there is the option to apply what you have learned within a case study. 

[Description]

DTPA is a chelating agent used for radioactive plutonium, americium, and curium. When bound to these radionuclides, DTPA accelerates renal elimination from the body in urine and effectively reduces the duration of radiation exposure the body receives. It is important to note that DTPA does not repair or protect the body from radiation damage, and is only effective for the specific radionuclides mentioned. To illustrate this fact, DTPA treatment may actually increase the deposition of uranium and neptunium into bone and is therefore not recommended treatment for contamination with these radionuclides.

There are two available forms of DTPA used to treat internal contamination – calcium-DTPA (Ca-DTPA) and zinc-DTPA (Zn-DTPA). Both are considered effective forms of treatment, but as will be discussed later, there are specific times when one form is preferred over the other.

[Availability]

If authorities determine it to be appropriate for a radiation emergency, the distribution of DTPA from state and federal stockpiles will be managed by public health agencies, and will then be administered by medical personnel.

[Indications]

Use of DTPA is indicated when individuals have been internally contaminated with a significant dose of radioactive plutonium, americium, and/or curium. When there is clinical suspicion of internal contamination, an exposure evaluation will be necessary to determine the amount of internal contamination and corresponding radiation dose. Clinical decision guides, or CDGs, can also help determine when DTPA is indicated. CDGs are discussed in another section of this training module.

Starting treatment as close to the time of exposure as possible is ideal. However, even in situations where DTPA is not immediately available it will still be helpful and should be provided when available.

Ca-DTPA and Zn-DTPA are used differently depending on when treatment is started and how long it lasts. Ca-DTPA is considered more effective in the first 24 hours, but carries higher risk of mineral depletion from the body if multiple doses are given over a long duration. However, more than 24 hours after exposure, Zn-DTPA is considered as effective as Ca-DTPA, and carries less long-term risk of mineral depletion. 

In the event that Zn-DTPA is not available, long-term treatment with Ca-DTPA is still indicated but should be given with a multivitamin supplement. Also, monitoring for mineral depletion, particularly zinc, magnesium, and manganese, should occur.

Both adults and children can receive either form of DTPA, but whenever possible, pregnant women should be provided only Zn-DTPA; in the absence of Zn-DTPA, it is better to treat with Ca-DTPA and a mineral supplement than to withhold treatment.

[Dosing and Administration]

DTPA can be administered intravenously or by nebulizer. Regardless of route, DTPA should be given as a single dose, once daily.

This chart provides detailed information regarding dose and treatment.

For adults receiving either Ca-DTPA or Zn-DTPA IV:

• 1g of DTPA solution, available as a single vial with a volume of 5 mL, can be administered via slow IV push over 3-4 minutes.   –OR–

• 1g of DTPA solution can be diluted in 100-250 mL of 5% Dextrose in Water, Ringers Lactate, or Normal Saline and administered over 30 minutes.

For adults receiving nebulized Ca-DTPA or Zn-DTPA :

• 1g of DTPA solution, can be 1:1 diluted with 5mL sterile water or Normal Saline, and inhaled over 15-20 minutes.

For children, safety has only been established for IV administration of Ca- and Zn-DTPA, and dose is calculated based on the child's weight.

When administered to children IV:

• 14 mg/kg/day, not to exceed 1 g/day, of Ca-DTPA or Zn-DTPA can be administered via slow IV push over 3-4 minutes.   –OR–

• 14 mg/kg/day, not to exceed 1 g/day, of Ca-DTPA or Zn-DTPA can be diluted in 100-250 mL of 5% Dextrose in Water, Ringers Lactate, or Normal Saline and administered over 30 minutes.

[Monitoring and Follow-up]

When possible, obtain baseline blood and urine samples - including CBC with differential, serum electrolytes and renal function, urinalysis, and blood and urine radiobioassays - before initiating treatment. Since radionuclides chelated by DTPA are eliminated in urine, treatment should be given cautiously in patients with impaired renal function.

During the course of treatment, samples of blood, urine, or feces may be collected to establish the effectiveness of treatment and/or the amount of radioactivity present. Testing for residual internal contamination should occur on a regular basis to determine when treatment can be terminated.

Individuals that receive DTPA should also be monitored for allergic and other adverse reactions.

[Adverse effects]

The main adverse effects of DTPA use include the depletion of certain essential minerals - especially zinc with Ca-DTPA.  Patients may also experience nausea, vomiting, chills, diarrhea, fever, pruritus, and muscle cramps.

For patients receiving nebulized DTPA, breathing difficulties may also occur.

[Contraindications]

There are no known contraindications for DTPA treatment.

[Special Considerations]

Ca-DTPA should be used cautiously in children, pregnant women, or in patients that have kidney disease, or hemochromatosis.  Nebulized DTPA treatment may be associated with exacerbations of asthma; so care should be taken when treating patients with a history of asthma.

Reminders:

• Pregnant women should be given Zn-DTPA where possible.   

• Extended treatment with Ca-DTPA should be given with accompanying vitamin supplement to address potential mineral depletion.