EVALUATION OF THE RENAL EXCRETION CHARACTERISTICS OF TC-99M MERCAPTOACETYLGLYCYL-D-ALANYLGLYCINE IN HEALTHY-VOLUNTEERS

During a study of C-methyl derivatives of technetium-99m mercaptoacetyltriglycine (Tc-99m-MAG3) it was found that the isomer of Tc-99m-mercaptoacetylglycyl-D-alanylglycine (Tc-99m-MAGAG-DA) is superior to Tc-99m-MAG3 with regard to its renal excretion characteristics in both mice and the baboon. We have now compared the renal handling of Tc-99m-MAGAG-DA and Tc-99m-MAG, in 6 healthy volunteers in a paired study. Renograms of Tc-99m-MAGAG-DA show a shorter time to renal maximum and a lower residual renal activity at 30 min post-injection (p.i.). The urinary excretion of Tc-99m-MAGAG-DA is higher at both 30 and 60 min p.i. The plasma concentration of Tc-99m-MAGAG-DA is lower than that of Tc-99m-MAG3 at each moment up to 60 min p.i., and the plasma clearance is accordingly higher. It is concluded that Tc-99m-MAGAG-DA is excreted more efficiently than Tc-99m-MAG3, but the preparation of Tc-99m-MAGAG-DA requires a HPLC purification step, and this limits its practical clinical usefulness.