New contrast agents. Chemistry and pharmacology.

Over the last two or three years, a considerable and almost universally favorable experience has been obtained in Europe with the low osmolality contrast agents. These agents, such as Hexabrix, iohexol and iopamidol have been shown to reduce the subjective pain and heat sensation associated with hyperosmolar agents. Hexabrix, although an ionic agent, has achieved a slightly greater reduction in osmolality than other low osmolality contrast agents. Low osmolality media have shown reduced chemotoxic effect on red cells, less histamine release, fewer electrocardiographic changes, and less marked hemodynamic changes compared with conventional agents. The new contrast media may be predictably safer, especially for high risk patients.