sup(99m)TC-ethylthiomethylphosphonate: a new renal scanning agent

A survey has been carried out of organic phosphonates as carriers for sup(99m)Tc in the hopes of correlating structure with organ localization. Scans of the sup(99m)Tc complexes of the simple phosphonates showed bone localization, but ethylthiomethylphosphonate showed only kidney localization. Details are given of the preparation of the sup(99m)Tc-ethylthiomethylphosphonate complex using either stannous chloride or formamidine sulfinic acid as reducing agent. A rabbit scan of the SnCl2 preparation after 2.5 hr showed that although most of the activity has been excreted by the kidneys, they were still well visualized. The kidneys were also well visualized after the first few minutes. Interference from liver or blood was negligible. Comparison of the tissue distribution and excretion of the two preparations in mice revealed differences in the localization dynamics. Acute toxicity in mice was low for both preparations. The results indicate the potential usefulness of sup(99m)Tc-ethylthiomethylphosphonate as a renal scanning agent. (U.K.)