The rabbit biodistribution of a therapeutic dose of zoledronic acid labeled with Tc-99m

The aim of the present study was to label a therapeutic dose of zoledronic acid (ZOL) with Tc-99m, evaluate its in vitro stability and compare its biodistribution to 99mTc-methylene biphosphonate (99mTc-MDP) in normal rabbits. Preparation of 0.50 mg of 99mTc-ZOL was carried out by the reduction of 99mTc-pertechnetate in the presence of stannous chloride. The radiolabeling efficiency was found to be greater than 99%. The labeled complex was stable at least up to 6 h at room temperature determined by paper chromatography. 99mTc-ZOL and 99mTc-MDP were administered intravenously to the rabbits for scintigraphic studies. Between 99mTc-ZOL and 99mTc-MDP, there were no significant differences in the ratios of femur/BG and lumbar vertebrae/BG, whereas epiphysis/BG and the kidney/BG ratios of 99mTc-MDP were higher than 99mTc-ZOL at the static studies.