Evaluation of the renal excretion characteristics of technetium-99m mercaptoacetylglycyl-D-alanylglycine in healthy volunteers.

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