Complement system activation by contrast media in neuroradiology.

Complement system activation was studied in six series of 12 patients undergoing routine contrast study following IV injection of five recently developed contrast media. The decreasing order of effectiveness on the complement system was as follows: ioxaglic acid, metrizamide, iodamidol. Metrizoic and ioxithalamic acids did not provoke any complement depletion at the doses used in this study. Both pathways of activating the complement system were involved. We could not find any definite correlation with osmolarity, ionic or nonionic formulation, protein binding, or hydrophobicity.