99mTc(CO)3(NTA) and 131I-OIH: Comparable plasma clearances in patients with chronic kidney disease

Abstract

The pharmacokinetics of the tricarbonyl core radiopharmaceutical 99mTc(CO)3-nitrilotriacetic acid (99mTc(CO) 3(NTA)) in rats and subjects with normal renal function are comparable to those of 131I-o-iodohippuran (131I-OIH), the radiopharmaceutical gold standard for the measurement of effective renal plasma flow. Our objective was to compare the pharmacokinetics of these 2 tracers in subjects with renal failure. Methods: 99mTc (CO)3(NTA) was prepared with commercially available NTA and a commercially available labeling kit and isolated by reversedphase high-performance liquid chromatography. Approximately 74 MBq (2.0 mCi) of 99mTc(CO)3(NTA) were coinjected with approximately 11.1 MBq (300 μCi) of 131I-OIH in 8 subjects with stage 3-4 renal failure; simultaneous images were obtained for 24 min, followed by an anterior image over the gallbladder and abdomen. Plasma clearances were determined from 10 blood samples obtained 3-180 min after injection using the single-injection, 2-compartment model. Plasma protein binding, red cell uptake, and percentage injected dose in the urine at 30 and 180 min were determined. Results: There was no difference in the plasma clearances of 99mTc(CO)3(NTA) and 131I-OIH (177 ± 63 vs. 171 ± 66 mL/min/1.73 m2, respectively) (P 5 0.41). The plasma protein binding and red cell uptake of 99mTc(CO) 3(NTA) were 35% ± 7% and 6% ± 3%, respectively; both values were significantly lower than the plasma protein binding (71% ± 5%) and red cell uptake (16% ± 2%) of 131I-OIH (P , 0.001). There was no significant difference in the percentage injected dose in the urine at 30 min (P 5 0.24) and at 3 h (P 5 0.82); for comparison, the percentage dose in the urine at 3 h was 77% ± 9% for 99mTc(CO) 3(NTA) and 78% ± 11% for 131I-OIH. Image quality with 99mTc(CO)3(NTA) was excellent and no activity was identified in the gallbladder or intestine. Conclusion: Results in patients with renal failure show the clearance and rate of urine excretion of 99mTc(CO)3(NTA) to be equivalent to that of 131I-OIH. COPYRIGHT © 2013 by the Society of Nuclear Medicine and Molecular Imaging, Inc.