Stability testing of iomeprol and iopamidol formulations subjected to X-ray radiation

Exposure of iodinated contrast media (ICM) to X-rays is not uncommon, as contrast media are often stored in close proximity to radiological equipment. However, the interaction between X-rays and ICM is not widely investigated in literature. The present study aims to investigate the chemical stability of iomeprol and iopamidol, two commercial iodinated ICM commonly used in diagnostic imaging, under X-rays exposure.

Different formulations of iopamidol and iomeprol (iodine concentration 9 to 400 mgI/mL, volume 50-500 mL) were exposed to three different conditions of X-ray irradiation: i) 1 month storage in CT room (≈5-15 mGy); (ii) low-dose protocol (≈10 mGy); (ii) stressed protocol (≈100 mGy). Unexposed and exposed solutions were characterized by high-performance liquid chromatography in terms of concentration of active pharmaceutical ingredient (API), iodine species and by products. In addition, appearance and colour of the solutions were inspected and pH measured.

API concentrations, appearance, colour and pH of the exposed formulations remained unaffected by X-rays. Measured concentrations of iodine species and by products were observed well within the acceptability criteria, i.e. values turned out to be lower than specifications limits established by the manufacturer, considering both release and shelf-life values.

Up to 100 mGy X-ray exposure did not induce any alteration of iomeprol and iopamidol formulation, nor a detectable increase in the concentration of iodine species or by-products.

Our study strengthens the hypothesis that ICM are stable under X-rays exposure up to 100 mGy.