Complexing of Tc-99m with cyclam: concise communication.

The macrocyclic amine, cyclam, has been found to be an efficient complexing agent for Tc-99m. Complexes can be formed in yields of higher than 95% at pH 11 in 10(-3) M cyclam using 5 x 10(-6) M SnC4H4O6 as a reducing agent. The complex is positively charged and is stable in air. It is not decomposed by dilution, by 0.05 M NaOH, or 0.05 M H2O2, but does show slight decomposition in 0.05 M HCl. In unanesthetized mice the complex is cleared rapidly from the blood by the kidneys and liver. Preliminary studies show that derivatives of cyclam also complex Tc-99m.