Technetium thiodiglycollic acid (99mTc-TDG). A new radiopharmaceutical with the potential for the assessment of renal function.

A mixture of hydrophilic complexes is formed on the reduction (employing tin metal as a reductant) of sodium pertechnetate 99mTc in the presence of the ligand thiodiglycollic acid (TDG). When administered to rats, the mixture demonstrated a renal clearance rate marginally greater than Glomerular filtration rate (GFR). HPLC analysis indicated the formation of two technetium complexes of TDG. After isolation of the complexes and their administration to rats, one (complex 1) showed renal clearance similar to that of 99mTc Diethylenetriamine pentaacetic acid (DTPA), while the other (complex 2) demonstrated renal clearance similar to that of 125I o-iodo hippuric acid. On heating the mixture of complexes, the proportion of the faster-clearing 99mTc TDG complex increased to 92% of the total activity, and the biodistribution of the material following heat rearrangement was equivalent to that of isolated complex 2.