title: Dosimetry of iodine-123-epidepride: a dopamine D2 receptor ligand.
abstract: Substituted benzamides have been shown to have very high affinity and specificity for the dopamine D2 receptor. One of these is radiolabeled epidepride, an iodine-substituted benzamide currently under evaluation as a SPECT imaging agent. Detailed estimates of the radiation absorbed dose to 26 organs and the whole body from [123I]epidepride have been calculated.
  
  
  METHODS
  The dosimetry calculations use a combination of in vivo uptake and biodistribution data from one rhesus monkey and seven humans to estimate residence times in eight organs. The computer program MIRDOSE2 was used to calculate the dosimetry.
  
  
  RESULTS
  Results indicate that 75% of the radioactivity is cleared through the urinary tract while the remaining radioactivity clears through the gallbladder and intestinal tract. The radiation absorbed dose can be minimized by administering a high lipid content meal 1.5 hr postinjection to empty the gallbladder and by giving large volumes of fluids throughout the study to induce increased urinary output.
  
  
  CONCLUSIONS
  By emptying the gallbladder and urinary bladder, the lower large intestine becomes the critical organ, 0.102 mGy/MBq (0.38 rad/mCi) followed by the upper large intestine, 0.092 mGy/MBq (0.34 rad/mCi). The effective dose equivalent is 0.025 mSv/MBq (0.092 rem/mCi).
authors.affiliation: Department of Radiology, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Votaw
authors.forename: M S
authors.initials: MS
authors.lastname: Ansari
authors.forename: N S
authors.initials: NS
authors.lastname: Mason
authors.forename: D
authors.initials: D
authors.lastname: Schmidt
authors.forename: T
authors.initials: T
authors.lastname: de Paulis
authors.forename: G
authors.initials: G
authors.lastname: Holburn
authors.forename: J A
authors.initials: JA
authors.lastname: Clanton
authors.forename: D B
authors.initials: DB
authors.lastname: Votaw
authors.forename: R G
authors.initials: RG
authors.lastname: Manning
authors.forename: R M
authors.initials: RM
authors.lastname: Kessler
mesh_terms: D000818:Animals; D001549:Benzamides / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D008253:Macaca mulatta; D008297:Male; D011759:Pyrrolidines / Q000493:pharmacokinetics*; D011829:Radiation Dosage; D017448:Receptors, Dopamine D2 / Q000032:analysis*; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D001549:Benzamides; D007457:Iodine Radioisotopes; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; C063525:epidepride