FDA Approves First New Drug Application for Treatment of Radiation Contamination due to Cesium or Thallium

The Food and Drug Administration (FDA) today approved a New Drug Application forRadiogardase, also known as Prussian blue, to treat people exposed to radiationcontamination, due to harmful levels of cesium-137 or thallium. Radiogardase capsulescontain Ferric (III) hexacyanoferrate(II).

The approval of Radiogardase is part of FDAs continuing efforts to provide theAmerican public with medical countermeasures in the event of a terrorist attack. Approvalfor Radiogardase was based on analysis of epidemiological studies and literature reportingon patients treated with Prussian blue in emergencies involving exposure to cesium-137 orthallium. Radiogardase works by increasing the rate of elimination of these substancesfrom the body.

FDA has taken a significant role in helping to speed the development of bioterrorismcountermeasures, said FDA Commissioner, Mark B. McClellan, M.D., Ph.D. This firstNDA approval for Radiogardase is part of the FDA initiatives aimed at bringing thesecritically important products to fruition.

For several decades, Prussian blue has been used to enhance the excretion of cesium-137and thallium from the body into the stool. Contamination with cesium-137 or thallium canoccur through a variety of routes including ingestion, inhalation, or wounds and can causeserious illness or death when high radiation doses are absorbed and delivered to criticalorgans. At lower doses such contamination has been associated with the development ofcancer.

Cesium-137 is widely used by industry and in medicine in a variety of devices and totreat certain cancers. Non-radioactive thallium is used in industry and as a rat poison.The radioactive form of thallium (thallium-201) is an approved drug used in small dosesfor medical imaging procedures. This use of radioactive thallium at low doses is verysafe.

Contamination by Cesium-137 is of particular concern because of its potential use as acomponent of a conventional explosive device containing radioactive material, commonlycalled a "dirty bomb." Although this radiological dispersal device is not anuclear bomb, it is detonated as a means to spread radioactive material and contaminatepeople and property.

Radiogardase is given orally. The main possible side effects are constipation and upsetstomach. Treatment should begin as soon as possible after exposure to radioactive cesiumor thallium. When the sources of radiation contamination are multiple or unknown, otherdrugs (such as potassium iodide) can be used together with Radiogardase.

The NDA for Radiogardase was sent to the agency in response to FDAs announcement inJanuary, 2003, that Prussian blue is safe and effective, when produced under conditionsspecified in approved marketing applications, for the treatment of exposure to radioactivethallium, non-radioactive thallium, or radioactive cesium. The national stockpile ofproducts for use in the event of an emergency includes stores of Prussian blue.

FDA has also determined that pentetate calcium trisodium (Ca-DTPA) and pentetate zinctrisodium (Zn-DTPA) are safe and effective, when produced under conditions specified inapproved marketing applications, for treatment of contamination with radioactive isotopesof the elements plutonium, americium and curium. FDA has encouraged manufacturers to usethese findings to submit marketing applications for these drug products to use as medicalcountermeasures.

More information about FDAs efforts to counteract bioterrorism is available onFDAs website at www.fda.gov/oc/opacom/hottopics/bioterrorism.html.