Clinical comparison of I-131 orthoiodohippurate and the kit formulation of Tc-99m mercaptoacetyltriglycine

Abstract

Previous studies in animals and humans have shown that technetium-99m mercaptoacetyltriglycine (MAG3) purified by high-performance liquid chromatography is a renal tubular agent with characteristics similar to those of iodine-131 orthoiodohippurate (OIH). A kit formulation for Tc-99m MAG3 has been developed and compared with I-131 OIH in 17 patients with suspected renal dysfunction and three potential kidney donors. There were no adverse reactions. Tc-99m MAG3 images were of good quality and consistently better than I-131 OIH images. There was no significant difference in the relative renal uptake of Tc-99m MAG3 and I-131 OIH. The 30-minute urinary excretion of Tc-99m MAG3 was 36.4%, versus 40.4% for I-131 OIH. The average plasma clearance of Tc-99m MAG3 (138 mL/min +/- 117) was less than that of I-131 OIH (272 mL/min +/- 205) (P less than .001); however, there was good correlation between the Tc-99m MAG3 and I-131 OIH clearances (r = .87). The volume of distribution of Tc-99m MAG3 (5.96 L +/- 1.94) was less than that of I-131 OIH (9.41 L +/- 3.73) (P less than .001). These characteristics and the advantages of a simple kit formulation should lead to widespread clinical use.