The pharmacokinetic properties of a bone-seeking radiopharmaceutical based on pentaphosphonic acid labeled with technetium-99m (99mTc-PPA) were investigated. The experiments were performed in healthy rats and in rats with a femoral bone-fracture (BF) model. The radiopharmaceutical was injected into a tail vein 14 days after the fracture. 99mTc-PPAshowed good stability in vivo because it accumulated in the thyroid less than unlabeled 99mTc. The maximum accumulation of 99mTc-PPA was found in bones tissue, where it reached 1.48 ±0.19% of injected dose per gram of tissue at 1 h after injection. The drug exhibited rapid blood clearance, showed minimum uptake into soft organs and tissues, and was excreted mainly via renal pathways. The presence of femoral BF significantly changed the biodistribution of 99mTc-PPAin soft organs and tissues. The 99mTc-PPAcontent in BF was 1.9 – 2.5 times higher than in healthy femur and 2 – 3 times higher than in skeleton. The concentration of 99mTc-PPAin other soft organs and tissues of rats with bone lesion was lower than in organs and tissues of healthy rats. The maximum BF-to-blood and BF-to-muscle ratios were 184.8 ±14.1 and 415.4 ±59.5, respectively, 3 h after injection. The results showed that 99mTc-PPAhad favorable properties for diagnosing bone-tissue metastases.
pharmacokinetic study radiopharmaceutical 99mTc-pentaphosphonic acid experimental bonefracture model technetium rats diagnostics bone-tissue metastases
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