99mTc(CO)3(NTA): A 99mTc Renal Tracer with Pharmacokinetic Properties Comparable to Those of 131I-OIH in Healthy Volunteers

• Authors: Andrew T Taylor Jr., Emory University; Malgorzata Lipowska, Emory University; Luigi G. Marzilli, Louisiana State University
• Journal Title: Journal of Nuclear Medicine and Radiation Therapy
• Volume: Volume 51, Number 3
• Publisher: Society of Nuclear Medicine | 2010-03, Pages 391-396
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.2967/jnumed.109.070813
• Subjects: Health Sciences, Pharmacology; Health Sciences, Radiology; Chemistry, General
• Keywords: 99mTc-tricarbonyl; renal radiopharmaceuticals; 99mTc(CO)3(NTA); 131I-ortho-iodohippurate (131I-OIH); 99mTc-mercaptoacetyltriglycine (99mTc-MAG3)

Abstract

Objectives Studies in rats showed that the pharmacokinetics of the tricarbonyl core radiopharmaceutical 99mTc(CO)3-nitrilotriacetic acid, 99mTc(CO)3(NTA), were essentially identical to those of 131I ortho-iodohippuran (131I-OIH), the clinical gold standard for the measurement of effective renal plasma flow. Our objective was to compare the pharmacokinetics of these two tracers in healthy volunteers. Methods 99mTc(CO)3(NTA) was prepared with commercially available NTA and a commercially available IsoLink kit (Covidien) and isolated by reversed-phased high-performance liquid chromatography. Approximately 74 MBq (2.0 mCi) of 99mTc(CO)3(NTA) were coinjected with 9.25 MBq (250 μCi) of 131I-OIH in nine volunteers, and simultaneous imaging of each tracer was performed for 24 min. Plasma clearances were determined from 8 blood samples obtained 3–90 min after injection using the single-injection, two-compartment model. Plasma protein binding, red cell uptake, and percentage injected dose in the urine at 30 and 180 minutes were determined. Results There was no difference in the plasma clearances of 99mTc(CO)3(NTA) and 131I-OIH, 475 ± 105 mL/min versus 472 ± 108 mL/min, respectively. The plasma protein binding and red cell uptake of 99mTc(CO)3(NTA) were 43 ± 5% and 9 ± 6%, respectively; both values were significantly lower (P < 0.001) than the plasma protein binding (75 ± 3%) and red cell uptake (17 ± 5%) of 131I-OIH. There was no significant difference in the percent injected dose recovered in the urine at 30 min and at 3 h; for comparison, the percent dose in the urine at 3 h was 91 ± 4% for 99mTc(CO)3(NTA) and 91 ± 6% for 131I-OIH (P = 0.96). Image quality with 99mTc(CO)3(NTA) was excellent, and the renogram parameters were similar to those of 131I-OIH. Conclusions Preliminary results in healthy volunteers suggest that the pharmacokinetic behavior of 99mTc(CO)3(NTA) is comparable to that of 131I-OIH.