The U.S. FDA approves 2 drugs for treating radiation contamination

The U.S. Food and Drug Administration has approved two drugs, pentetate calcium trisodium injection (Ca-DTPA) and pentetate zinc trisodium injection (Zn-DTPA) for treating certain kinds of radiation contamination. The FDA is approving these two drugs as part of its ongoing effort to provide the American public the best available protection against nuclear accidents and terrorist threats.

The FDA has determined that Ca-DTPA and Zn-DTPA are safe and effective for treating internal contamination with plutonium, americium, or curium. The drugs increase the rate of elimination of these radioactive materials from the body.

The two drugs have been used for several decades as investigational drugs to treat patients in radiation contamination emergencies. In order to encourage submission of new drug applications for these products, the FDA announced in September 2003, specific conditions and findings under which the two drugs could be approved through new drug applications. Until today, there had been no approved drug products for the treatment of internal contamination with plutonium, americium, or curium.

Internal contamination with plutonium, americium, or curium can occur through a variety of routes including ingestion, inhalation, or direct contact through wounds. The goal of treatment with Ca-DTPA and Zn-DTPA is to enhance the removal of these radioactive contaminants and therefore the risk of possible future biological effects including the development of certain cancers, which may occur years after exposure.

Release of plutonium, americium and curium could occur from laboratory or industrial accidents; or through terrorist attacks using a radiation dispersal device (RDD), commonly known as a “dirty bomb”.

Ca-DTPA and Zn-DTPA should not be administered simultaneously. If both products are available, Ca-DTPA should 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. Ca-DTPA and Zn-DTPA are usually administered into the blood stream, however in people whose contamination is only by inhalation, Ca-DTPA or Zn-DTPA can be administered by nebulized inhalation.

The main side effect of Ca-DTPA is the loss of certain essential nutritional metals such as zinc, which can be replaced by taking oral zinc supplements. Although Zn-DTPA may also decrease the levels of certain nutritional metals, the effect is less than with Ca-DTPA. In addition, breathing difficulties have been noted in some individuals treated by inhalation therapy with these products.

Plutonium is a heavy, radioactive, man-made metallic element with atomic number 94 and whose most important isotopes (fissile PU-239 and PU-241) are both produced by neutron irradiation of the uranium isotope U-238. Used for reactor fuel and in nuclear weapons.

Americium is a radioactive metallic element produced by the radioactive decay of certain plutonium isotopes after bombardment of uranium, neptunium, and/or plutonium with high-energy neutrons.

Curium is a radioactive transuranic metallic element; produced by bombarding plutonium with helium nuclei.

http://www.fda.gov