Iodine-131-labeled diphosphonates for the palliative treatment of bone metastases: I. Organ distribution and kinetics of I-131 BDP3 in rats.
I-131-labeled alpha-amino-(4-hydroxybenzylidene)-diphosphonate (BDP3) was examined in Sprague-Dawley rats for its bone affinity and other biokinetical characteristics. Iodine-131 BDP3 exhibited high bone affinity, with rapid blood clearance and renal excretion. Total-body retention measurements revealed an effective half-life of the activity of t1/2 = 169 hr. Similar kinetics were found in rat femurs, with t1/2 = 158 hr. Rats bearing osteosarcomas showed an enhanced uptake with a slower clearance (t1/2 = 177 hr). The amount of I-131 BDP3 excreted in urine agreed with the total body retention values. Fifty percent was excreted in the urine, as unchanged I-131 BDP3, by 24 hr after application. Almost no activity was found in the feces of the rats. LD50 measurements in rats amounted to 64 mg/kg. Because of these biokinetical characteristics and the simple labeling procedure, I-131 BDP3 is suggested as a radiopharmaceutical for the palliative treatment of pain that often accompanies disseminated bone metastases.
D000818:Animals; D001597:Benzylidene Compounds / Q000378:metabolism; D001859:Bone Neoplasms / Q000532:radiotherapy* / Q000556:secondary; D004164:Diphosphonates / Q000378:metabolism; D007457:Iodine Radioisotopes / Q000627:therapeutic use*; D008297:Male; D012516:Osteosarcoma / Q000532:radiotherapy / Q000556:secondary; D010166:Palliative Care; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution
D001597:Benzylidene Compounds; D004164:Diphosphonates; D007457:Iodine Radioisotopes; C043715:alpha-amino-(4-hydroxybenzylidene)diphosphonate