Clinical comparison of technetium-99m-EC, technetium-99-m-MAG3 and Iodine-131-OIH in renal disorders

Technetium-99m-ethylenedicysteine has recently been developed for renal function studies. The pharmacokinetics of 99mTc-EC were studied by constant infusion technique and compared with 99mTc-MAG3 and 131I-OIH in 11 patients with various renal disorders. After giving a 7.4 MBq 131I-OIH and 90-110 MBq 99mTc-EC or 99mTc-MAG3 bolus, a constant infusion (MBq/ml) 99mTc--agent and 0.07 MBq/m 131I-OIH was started. Sixteen blood and five urine samples were obtained over three hr. The renal clearance of 99mTc-EC was higher than than of 99mTc-MAG3. The 99mTc-EC/OIH and 99mTc-MAG3/OIH ratios were 0.75 ± 0.05 and 0.55 ± 0.10 (p=0.00087), respectively. The distribution volume of 99mTc-EC was also higher than that of 99mTc-MAG3 (15722 ± 4644 and 9509 ± 2788 ml/1.73m2, respectively; p=0.072). The 99mTc-EC/OIH and 99mTc-MAG/OIH distribution volume ratios were 1.03 ± 0.14 and 0.55 ± 0.10, respectively (p = 0.0003). The 60-min excretion values of 99mTc-EC and 99mTc-MAG3 were compared to that of OIH. The 99mTc-EC/OIH and 99mTc-MAG3/OIH excretion ratios were 0.96 ± 0.06 and 1.07 ± 0.10, respectively (p=0.162). The protein binding of 99m-EC and OIH were found to be 34% ±4 and 66% ±5, respectively (p<0.0001). The red cell binding of 99mTc-EC was negligible (3% ±1.2) in comparison to OIH (27% ±3; p< 0.0001). This limited study demonstrates the pharmacokinetic and renal clearance properties of 99mTc-EC. This agent has good potential for renal function evaluation. 32 refs., 5 tabs