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Introduction

  1. Pharmacology. Insoluble Prussian blue (ferric hexacyanoferrate) has been used to treat radioactive and nonradioactive cesium and thallium poisonings. Owing to the long half-lives of these isotopes, ingestion can pose significant long-term health risks. Insoluble Prussian blue binds thallium and cesium in the gastrointestinal tract as they undergo enterohepatic recirculation, enhancing fecal excretion. Proposed mechanisms of binding include chemical cation exchange, physical adsorption, and mechanical trapping within the crystal lattice structure. Insoluble Prussian blue is not absorbed across the intact GI wall.
  2. Indications. Known or suspected internal contamination by:
    1. Radioactive cesium (eg, 137Cs) and nonradioactive cesium.
    2. Radioactive thallium (eg, 201Tl) and nonradioactive thallium.
  3. Contraindications. There are no absolute contraindications. The efficacy of the agent relies on a functioning GI tract; thus, ileus may preclude its use and effectiveness.
  4. Adverse effects
    1. Upset stomach and constipation.
    2. May bind other elements, causing electrolyte or nutritional deficits.
    3. Does not treat the complications of radiation exposure.
    4. Blue discoloration of feces (and teeth if capsules are opened).
    5. Use in pregnancy. FDA Category C (indeterminate Introduction). Because Prussian blue is not absorbed from the GI tract, effects on the fetus are not expected.
  5. Drug or laboratory interactions
    1. No major interactions.
    2. May decrease absorption of tetracycline.
  6. Dosage and method of administration. Prussian blue is kept in the Strategic National Stockpile (SNS) at the Centers for Disease Control and Prevention (CDC). The Radiation Emergency Assistance Center/Training Site (REAC/TS) can be contacted for information on obtaining Prussian blue and its recommended dosing by telephone at 1-865-576-3131(business hours) or 1-865-576-1005 (available 24 hours) or on the Internet at www.orau.gov/reacts.
    1. Adults and adolescents. Usual dose is 3 g orally three times daily (9 g daily), although higher doses (>10 g daily) are often used for acute thallium poisoning (particularly if thallium is present in the GI tract). Doses may be decreased to 1-2 g three times daily when internal radioactivity is reduced and to improve patient tolerance.
    2. Pediatrics (2-12 years): 1 g orally three times daily.
    3. Capsules may be opened and mixed with food or water for those who have difficulty swallowing. This may cause blue discoloration of the mouth and the teeth.
    4. Co-ingestion with food may increase effectiveness by stimulating bile secretion.
    5. Treatment should continue for a minimum of 30 days. The duration of treatment should be guided by the level of contamination as measured by the amount of residual whole-body radioactivity.