Evaluation of Tc-99m mercaptoacetyltriglycine in patients with impaired renal function.

Technetium-99m mercaptoacetyltriglycine (MAG3), a new radiopharmaceutical shown to have biological properties similar to iodine-131 o-iodohippurate (OIH) in animals and healthy volunteers, was compared with OIH in 15 patients with varying degrees of renal impairment. The Tc-99m MAG3 images were uniformly superior, regardless of the serum creatinine level. There was no significant difference in the 30-minute blood clearance of OIH and MAG3. MAG3 protein binding (78.6%) was greater than that of OIH (53.1%) (P less than or equal to .01), and the volume of distribution of MAG3 (7.06 liters) was less than that of OIH (10.78 liters) (P less than or equal to .01). In six patients the 30-minute urinary excretion of the two agents was essentially identical. The time to the peak height of the renogram curves was more rapid for MAG3 than for OIH using both cortical and whole-kidney regions of interest (P less than or equal to .02). In summary, preliminary results suggest that Tc-99m MAG3 performs well in patients with impaired renal function and may well be an acceptable replacement for OIH. A kit formulation is currently undergoing clinical evaluation.