The preparation and composition of HIDA.

The compositions of four "brands" of Tc-HIDA-dimethyl HIDA (Sorin Biomedica), diethyl HIDA (Solco), diethyl HIDA (The Radiochemical Centre), and para-butyl HIDA (Sorin Biomedica)--were investigated at varying times after their preparation from "instant kits", by using Sephadex gel column chromatography. Up to three peaks of activity were seen in each chromatogram, representing free reduced technetium, the monocomplex, and the biscomplex of Tc-HIDA respectively. In all cases the free reduced technetium component diminished to reach a plateau at less than 4% of total activity, by 1 h. In both "brands" of diethyl HIDA there was a transformation from the monocomplex to the biscomplex which took about one hour. The rate of this transformation was increased by raising the temperature of incubation, or by agitation during incubation. In the para-butyl HIDA this transformation was again noted, but was incomplete. In the dimethyl HIDA the monocomplex form was not seen. There was no noticeable disintegration of any Tc-HIDA complex up to 6 h. It is suggested that HIDA should be incubated for 1 h after preparation, before use, to achieve a stable composition.