title: Facing the nuclear threat: thyroid blocking revisited.
abstract: BACKGROUND
  People being exposed to potentially harmful amounts of radioactive iodine need prophylaxis to prevent high radiation-absorbed doses to the thyroid.
  
  
  OBJECTIVE
  Parameters determining the individual protective effect of a pharmacological intervention were investigated.
  
  
  METHODS
  Biokinetics of (123)I was evaluated in 27 healthy volunteers (aged 22-46 yr, median 25 yr, in total 48 assessments) twice in a baseline measurement of the undisturbed kinetics and in an intervention assessment 48 h later.
  
  
  METHODS
  Seven regimens using single doses of potassium iodide (KI) or sodium perchlorate (SP) at different times relative to exposure were compared: 100 mg KI (-24, 2, 8, 24 h), 100 mg SP (2 h), or 1 g SP (2, 8 h).
  
  
  METHODS
  Different drugs and dosages and the influence of individual parameters of iodine kinetics should be tested.
  
  
  RESULTS
  Mean dose reductions for interventions at -24, 2, 8, and 24 h relative to the activity incorporation were 88.7, 59.7, 25.4, and 2.8%, respectively. One gram SP was equally effective as 100 mg KI; residual uptake was observed after 100 mg SP. The individual dose reduction decreased exponentially with the effective half-life of the activity in the blood. Kinetics in subjects older than 40 yr was as assumed in official guidelines for the prophylaxis after nuclear accidents but was faster in younger participants.
  
  
  CONCLUSIONS
  Data on the efficacy of thyroid blocking used in the guidelines are adequate for older people but not for young individuals with their typically faster kinetics. SP may be used for thyroid blocking as alternative for individuals with iodine hypersensitivity.
authors.affiliation: Department of Nuclear Medicine, University of Würzburg, Oberdürrbacher Straße 6, D-97080 Würzburg, Germany. haenscheid@nuklearmedizin.uni-wuerzburg.de
authors.forename: Heribert
authors.initials: H
authors.lastname: Hänscheid
authors.forename: Christoph
authors.initials: C
authors.lastname: Reiners
authors.forename: Guennadi
authors.initials: G
authors.lastname: Goulko
authors.forename: Markus
authors.initials: M
authors.lastname: Luster
authors.forename: Marcus
authors.initials: M
authors.lastname: Schneider-Ludorff
authors.forename: Andreas K
authors.initials: AK
authors.lastname: Buck
authors.forename: Michael
authors.initials: M
authors.lastname: Lassmann
mesh_terms: D000328:Adult; D000367:Age Factors; D005260:Female; D006207:Half-Life; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D010472:Perchlorates / Q000008:administration & dosage / Q000627:therapeutic use*; D011193:Potassium Iodide / Q000008:administration & dosage / Q000627:therapeutic use*; D018788:Radioactive Hazard Release; D017670:Sodium Compounds / Q000008:administration & dosage / Q000627:therapeutic use*; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*
chemical_list: D007457:Iodine Radioisotopes; D010472:Perchlorates; D017670:Sodium Compounds; D011193:Potassium Iodide; C031068:sodium perchlorate