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Ferric Hexacyanoferrate


(FER ik hex a SYE an oh fer ate)

Index Terms

  • Ferric (III) Hexacyanoferrate (II)
  • Ferric Ferrocyanide
  • Insoluble Prussian Blue
  • Prussian Blue

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling.

Capsule, Oral:

Radiogardase: 0.5 g

Brand Names: U.S.

  • Radiogardase

Pharmacologic Category

  • Antidote


The ferric hexacyanoferrate lattice preferentially binds cesium and thallium isotopes in the gastrointestinal tract following their ingestion or excretion in the bile (thereby, blocking reabsorption). The resulting complex is eliminated in the feces reducing the absorption of thallium or the radioactive residence time of cesium (Kazzi 2015).


Ferric hexacyanoferrate: Oral: None


Ferric hexacyanoferrate: Feces (99%, unchanged) (Radiogardase, 2008)

Half-Life Elimination

Cesium-137: Effective: Adults: 80 days, decreased by 69% with ferric hexacyanoferrate; adolescents: 62 days, decreased by 46% with ferric hexacyanoferrate; children: 42 days, decreased by 43% with ferric hexacyanoferrate

Nonradioactive thallium: Biological: 8 days; with ferric hexacyanoferrate: 3 days

Special Populations: Hepatic Function Impairment

May be less effective because of decreased biliary excretion of cesium and thallium.

Use: Labeled Indications

Internal contamination: Ferric hexacyanoferrate (also known as Prussian blue) is an orally available cation exchange resin that is indicated for the treatment of patients with known or suspected internal contamination with radioactive cesium and/or radioactive or nonradioactive thallium to increase their rates of elimination.


There are no contraindications in the manufacturer’s labeling.

Dosing: Adult

Internal contamination with radioactive cesium and/or radioactive or nonradioactive thallium: Oral: Note: Treatment should begin as soon as possible following exposure, but is also effective if therapy is delayed. Treatment typically continues for ≥30 days.

Cesium exposure: 1 to 3 g 3 times daily (REMM 2014)

Manufacturer's labeling: Dosing in the prescribing information may not reflect current clinical practice. 3 g 3 times daily

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Internal contamination with radioactive cesium and/or radioactive or nonradioactive thallium: Oral: Note: Treatment should begin as soon as possible following exposure, but is also effective if therapy is delayed. Treatment typically continues for ≥30 days.

Children 2 to 12 years: 1 g 3 times daily

Adolescents: Refer to adult dosing.


Oral: In critically ill patients who cannot swallow, capsules may be opened and administered by orogastric or nasogastric tube (Hoffman 2019). Also, the capsules may be opened and mixed with bland food or liquid. Administer with food to stimulate excretion of cesium or thallium. Increase dietary fiber or take with fiber laxative to decrease constipation.

Dietary Considerations

Take with food. A high-fiber diet or fiber laxative is recommended to avoid constipation.


Store at 20°C to 25°C (68°F to 77°F); excursions permitted between 15°C and 30°C (59°F and 86°F). Brief exposure to temperatures up to 40°C (104°F) may be tolerated provided the mean temperature does not exceed 25°C (77°F); however, minimize such exposure.

Drug Interactions

There are no known significant interactions.

Adverse Reactions

Frequency not always defined.

Gastrointestinal: Constipation (24%), fecal discoloration (blue), gastric distress

Endocrine & metabolic: Hypokalemia (7%)


Concerns related to adverse effects:

• Discoloration: Feces will turn blue; if capsule contents are opened and eaten with food, oral mucosa and detention may also be colored blue.

Disease-related concerns:

• Cardiac arrhythmias: Use with caution in patients with preexisting cardiac arrhythmias; may cause electrolyte imbalances.

• Electrolyte imbalances: May bind to electrolytes in the GI tract. Use with caution in patients with electrolyte imbalances.

• Gastric immotility: Use with caution in patients with decreased gastric motility; constipation should be avoided to prevent increased radiation absorption from the gastrointestinal tract. Increase dietary fiber or take with fiber laxative to decrease constipation.

Other warnings/precautions:

• Radiation exposure: Patients should be instructed to minimize radiation exposure to others or re-exposure to self.

• Radiation toxicity: Appropriate use: Ferric hexacyanoferrate increases the rate of elimination of thallium and cesium; it does not treat complications of radiation exposure. Supportive treatment for radiation toxicity should be given concomitantly. Additional decontamination and/or treatment may be needed if exposure to other radioactive isotopes is known or suspected.

Monitoring Parameters

Bowel movements; CBC with differential and platelets and electrolytes weekly

Baseline cesium and/or thallium exposure (whole body counting and/or bioassay, feces or urine sample); urine and fecal cesium and/or thallium weekly during therapy; residual whole body radioactivity after 30 days of treatment

Pregnancy Risk Factor


Pregnancy Considerations

Animal reproduction studies have not been conducted. Ferric hexacyanoferrate is not absorbed from the gastrointestinal tract and is not expected to affect the fetus. Cesium-137 crosses the placenta; in one case, reported levels were equal in the mother and the neonate. Thallium also crosses the placenta; fetal death and failure to thrive have been reported. Toxicity from exposure to thallium or radioactive cesium is expected to be greater than the risk of toxicity to ferric hexacyanoferrate. In general, medications used as antidotes should take into consideration the health and prognosis of the mother; antidotes should be administered to pregnant women if there is a clear indication for use and should not be withheld because of fears of teratogenicity (Bailey, 2003).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience mouth discoloration or stool discoloration. Have patient report immediately to prescriber signs of low potassium (muscle pain or weakness, muscle cramps, or an abnormal heartbeat), or severe constipation (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.