In vivo activation of serum complement by contrast media: a clinical study.

The study was designed to confirm complement system activation in vivo in man after intravenous injection of contrast media for brain CT scan enhancement. Four currently available components were tested: C1q, C3 activator, C3c, and C4 after intravenous injection of seven different contrast media: diatrizoate, metrizoate, iothalamate, ioxithalamate, ioxaglate, metrizamide, iopamidol. The complement system was indeed activated by certain control media, but no correlation with clinical reactions or with hypertonicity, ionic or nonionic formulation, or protein binding could be found. However, a correlation was found to some extent between the lipid solubility and the activity on the complement system. Addition of calcium salts definitely inhibited the complement system activation induced by metrizoate and ioxaglate.