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In vivo activation of serum complement by contrast media: a clinical study
Insights
Contrast media used in brain CT scans can activate the complement system in the body. Lipid solubility of the media correlated with this activation, while calcium salts inhibited it.
Area of Science:
- Immunology
- Radiology
- Pharmacology
Background:
- Intravenous contrast media are essential for brain CT scans.
- Potential adverse reactions to contrast media are a concern.
- The complement system is a key part of innate immunity.
Purpose of the Study:
- To investigate in vivo complement system activation by contrast media in humans.
- To identify factors influencing contrast media-induced complement activation.
Main Methods:
- Four complement components (C1q, C3 activator, C3c, C4) were measured.
- Seven different intravenous contrast media were administered to subjects.
- Clinical reactions, hypertonicity, formulation, protein binding, and lipid solubility were assessed.
Main Results:
- Complement system activation was observed with certain contrast media.
- No correlation was found between activation and clinical reactions, hypertonicity, formulation, or protein binding.
- Lipid solubility showed a correlation with complement system activity.
- Calcium salts inhibited complement activation induced by specific contrast media (metrizoate, ioxaglate).
Conclusions:
- Specific intravenous contrast media can activate the human complement system in vivo.
- Lipid solubility is a potential factor influencing this activation.
- Calcium salts may mitigate contrast media-induced complement activation.
Abstract:
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.