Comparison of biological characteristics of EDTMP complexes with 99mTc, 111In and 153Sm in rats

The pharmacokinetics and elimination of EDTMP chelates with different radionuclides (99mTc, 111In and 153Sm) has been investigated in rats. The biodistribution of the complexes under study was similar and two main processes, namely bone uptake and the elimination of glomerular filtration, take part in their rapid blood clearance. A substantially slower blood clearance of 111In-EDTMP in comparison with the other complexes suggests partial indium exchange between the chelate and transferrin. All the complexes exhibited high affinity for bone and the radionuclide uptake into the skeleton was in the order 153Sm > 111In > 99mTc. No specific extra-skeletal uptake was found.