Radiopharmacokinetics, renal clearance and dosimetry of 99mTc-MAG3

Technetium-99m-mercaptoacetyltriglycine (99mTc-MAG3) is a radiopharmaceutical for tubular function and can be prepared with 99m-technetium and the ligand Bz-MAG3 (Instituto Nacional de Investigaciones Nucleares, Mexico City). No radiopharmacokinetic parameters have been found for the healthy adult Mexican population with 99mTc-MAG3, prepared with the nationally produced or imported Bz-MAG3 kit.

The radiopharmacokinetic parameters and the clearance of 99mTc-MAG3 in seven healthy Mexican volunteers were determined by the single- and multi-sample methods. Computer programs were used for the calculations.

Using several plasma samples from 0-43 min and the BIEXP program, it was shown that 99mTc-MAG3 follows a two-compartment model of distribution, with an apparent volume in the central compartment Vdcc = 3.8 + 0.7 l, a volume of distribution at steady state Vdss = 6.7 + 1.0 l, T1/2 alpha = 0.07 + 0.02 h-1, T1/2 beta = 0.49 + 0.15 h-1, mean residence time MRT = 0.60 + 0.17 h and clearance = 208 + 57 (ml/min)/1.73 m2. In comparison, the clearance value with a single sample drawn 43 min post-injection and calculated with Tauxe's formula was 193 +/- 59 (ml/min)/m2.

The 15 ml difference between the two methods is neither statistically different (p = 0.11) nor important for routine clinical studies. The single-sample method is recommended because it is reliable and can be done at the same time that the dynamic renal scan is acquired. Estimated absorbed radiation dose was calculated for several organs.