title: Quantitative measurement of cyanide released from Prussian Blue.
abstract: BACKGROUND
  Prussian Blue (PB), ferric hexacyanoferrate is indicated for (oral) treatment of internal contamination with radioisotopes of cesium or thallium. Cyanide is 35-40% of PB's molecular composition, thus cyanide may be released during transit through the digestive tract under physiological pH. The U.S. Food and Drug Administration investigated the issue of cyanide release prior to drug approval to ensure the drug's benefits exceeded risks.
  
  
  OBJECTIVE
  To determine cyanide released from PB under pH conditions that bracket human physiological exposure.
  
  
  METHODS
  PB was incubated in situ at pH 1.0-12, 37 degrees C for 1-48 hours. Cyanide was measured using a validated colorimetric method by UV-VIS spectroscopy.
  
  
  RESULTS
  PB had the highest cyanide release at pH 1 (135 ug/g) and lowest release at pH 5.0-7.0 from the highest daily dose of PB (17.5 g) (21 ug/g). Considering the minimal lethal dose of cyanide is approximately 50 mg, the maximal cyanide released (1.6 mg) does not present a safety concern.
authors.affiliation: Food and Drug Administration, Center for Drug Evaluation and Research, Division of Product Quality Research, Silver Spring, Maryland 20993, USA.
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Yang
authors.forename: Charles
authors.initials: C
authors.lastname: Brownell
authors.forename: Nakissa
authors.initials: N
authors.lastname: Sadrieh
authors.forename: Joan
authors.initials: J
authors.lastname: May
authors.forename: Alfred
authors.initials: A
authors.lastname: Del
mesh_terms: D000931:Antidotes; D002588:Cesium Radioisotopes / Q000506:poisoning; D005295:Ferrocyanides / Q000737:chemistry*; D006856:Hydrogen Cyanide / Q000032:analysis* / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D013997:Time Factors
chemical_list: D000931:Antidotes; D002588:Cesium Radioisotopes; D005295:Ferrocyanides; D006856:Hydrogen Cyanide; C000170:ferric ferrocyanide