Pentetic acid

DTPA
IUPAC name	[[(Carboxymethyl)imino]bis(ethylenenitrilo)]- tetra-acetic acid
Other names	DTPA, Diethylene triaminepentaacetic acid, Diethylenetriamine- N,N,N',N',N"-pentaacetic acid, N,N-Bis(2-(bis-(carboxymethyl)amino)ethyl)-glycine, Pentetic acid
Identifiers
CAS number	67-43-6 Y
RTECS number	MB8205000
SMILES	O=C(O)CN(CCN(CC(=O)O)CC (=O)O)CCN(CC(=O)O)CC(=O)O
Properties
Molecular formula	C14H23N3O10
Molar mass	393.35 g/mol
Appearance	White crystalline solid
Melting point	220°C (493.15 K, 428°F)
Boiling point	decomposes at a higher temp.
Solubility in water	<0.5g/100ml
Hazards
Flash point	Does not burn
Related compounds
Related compounds	EDTA, NTA
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Diethylene triamine pentaacetic acid (DTPA) is a polyamino carboxylic acid consisting of a diethylenetriamine backbone modified with five carboxymethyl groups. The molecule can be viewed as an expanded version of EDTA. DTPA is used as its conjugate base, often undefined, which has a high affinity for metal cations. Upon complexation to lanthanide and actinide ions, DTPA exists as the pentaanionic form, i.e. all five carboxylic acid groups are deprotonated. In contrast to EDTA the compound possesses 7 centres to form coordination bonds with metals.^[1] Most metals are only capable of forming six such bonds. So, after compexation with a metal, the molecule still has a "handle" which can be used to couple it to other compounds, as is shown by its derivative pendetide.

Uses

Medical

• Since the 1960s, doctors have used DTPA as a chelating agent to treat internal contamination from radioactive materials such as americium, plutonium, californium, curium, and berkelium. Currently, DTPA is approved by the U.S. Food and Drug Administration (FDA) for chelation of only three radioactive materials: plutonium, americium, and curium.
• In ibritumomab tiuxetan, the chelator tiuxetan is a modified version of DTPA whose carbon backbone contains an isothiocyanatobenzyl and a methyl group.^[2]
• In capromab pendetide and satumomab pendetide, the chelator pendetide (GYK-DTPA) is a modified DTPA containing a peptide linker used to connect the chelate to an antibody.^[3]
• Pentetreotide is a modified DTPA attached to a peptide segments.^[4]
• DTPA and derivatives are used to chelate gadolinium to form a MRI contrast agent, such as Magnevist.
• Technetium is chelated with DTPA for ventilation perfusion scan (V/Q scan) and renal scan.^{[citation needed]}

Other use

• DTPA is used as a soil extractant for available soil micronutrients like Zn, Fe, Cu and Mn at the pH of 7.3 with Calcium chloride and TEA.^{[citation needed]}

Coordination chemistry

DTPA is the parent acid of an octadentate ligand, diethylene triamine pentaacetate. In some situations, all five acetate arms are not attached to the metal ion. It has been used to decontaminate humans who have been poisoned with plutonium, americium and other actinides. Upon formation of chelate complexes, heavy metal ions are less readily absorbed and are more apt to be eliminated in urine. It is normally used as the calcium or zinc salt. When given within the first day after internal contamination has occurred, Ca-DTPA is about 10 times more effective than Zn-DTPA at chelating plutonium, americium, and curium. After 24 hours have passed, Ca-DTPA and Zn-DTPA are equally effective in chelating these radioactive materials.^{[citation needed]} "Internal contamination" is jargon for the unintentional ingestion of radioactive materials. Most cases of internal contamination result from working with radioactive materials. (http://www.bt.cdc.gov/radiation/dtpa.asp).

Efficacy

DTPA cannot bind all of the radioactive materials that might get into a person’s body after a radiological or nuclear event, such as a terrorist attack with a “dirty bomb.” This medicine cannot prevent radioactive materials from entering the body. DTPA cannot reverse the health effects caused by radioactive materials once these materials have entered the body.

Chelating agents work best when given shortly after radioactive materials or poisons have entered the body. The more quickly a radioactive material or poison is removed from the body, the fewer and less serious the health effects will be. After 24 hours, plutonium, americium, and curium are harder to chelate. However, DTPA can still work to remove these radioactive materials from the body several days or even weeks after a person has been internally contaminated.

Safety

DTPA does not build up in the body or cause long-term health effects. People who are given repeat doses of Ca-DTPA within a short period of time may have nausea, vomiting, diarrhea, chills, fever, itching, and muscle cramps. Other side effects may include headache, lightheadedness, chest pain, and a metallic taste in the mouth.

Ca-DTPA (and Zn-DTPA) can chelate certain important minerals that the body needs (zinc, magnesium, and manganese). For example, the body needs zinc to make red blood cells, white blood cells, and platelets. Therefore, DTPA treatment may interfere with the normal production of blood cells. As a precaution, patients receiving long-term treatment with DTPA should be given a vitamin and mineral supplement that contains zinc.

References

This article incorporates material from Facts about DTPA, a fact sheet produced by the United States Centers for Disease Control and Prevention.