Technetium-99m-ethylenedicysteine has recently been developed for renal function studies. The pharmacokinetics of Tc-99m-EC were studied by constant infusion technique and compared with Tc-99m-MAG3 and I-131-OIH in, 11 patients with various renal disorders. Methods: After giving a 7.4 MBq I-131-OIH and 90-110 MBq Tc-99m-EC or Tc-99m-MAG3 bolus, a constant infusion (1 MBq/ml Tc-99m-agent and 0.07 MBq/m I-131-OIH was started. Sixteen blood and five urine samples were obtained over three hr. Results: The renal clearance of Tc-99m-EC was higher than that of Tc-99m-MAG3. The Tc-99m-EC/OIH and (99m)TcMAG3/OIH ratios were 0.75 +/- 0.05 and 0.55 +/- 0.10 (p = 0.00087), respectively. The distribution volume of Tc-99m-EC was also higher than that of Tc-99m-MAG3 (15722 +/- 4644 and 9509 +/- 2788 m1/1.73m(2), respectively; p = 0.072). The Tc-99m-EC/OIH and Tc-99m-MAG3/OIH distribution volume ratios were 1.03 +/- 0.14 and 0.55 +/- 0.10, respectively (p = 0.0003). The 60-min excretion values of Tc-99m-EC and Tc-99m-MAG3 were compared to that of OIH. The Tc-99m-EC/OIH and Tc-99m-MAG3/OIH excretion ratios were 0.96 +/- 0.06 and 1.07 +/- 0.10, respectively (p = 0.162). The protein binding of Tc-99m-EC and OIH were found to be 34% +/- 4 and 66% +/- 5, respectively (p < 0.0001). The red cell binding of Tc-99m-EC was negligible (3% +/- 1.2) in comparison to OIH (27% +/- 3; p < 0.0001). Conclusion: This limited study demonstrates the pharmacokinetic and renal clearance properties of Tc-99m-EC. This agent has good potential for renal function evaluation
