Sup(99m)Tc bone scanning agents: Pt. 6

The plasma binding of Tc-complexes of pyrophosphate, MDP and HMDP was investigated in vitro using gel chromatography on Biogel P-200. Binding percentages ranging from 5-15% were found. The pH of the preparation of the radiopharmaceutical had a large effect on the protein binding. The differences between the three ligands used were small. The chemical composition of the complexes was investigated for Tc(Sn)pyrophosphate using gel chromatography on Biogel P-4. The protein-bound technetium was not attached to pyrophosphate. The chemical composition of the unbound Tc-complex is discussed. Finally a comparison is made with literature data. It is concluded that protein binding plays a minor role. (author)