Numerous types of intravascular contrast media have been used to improve medical imaging. Their value has long been accepted, as confirmed by their common daily use in radiology departments around the world. However, like all pharmaceuticals, these agents are poisons and are not completely risk-free (American College of Radiology, 2013). The safety of contrast media depends on their composition. There are various types of contrast that vary in composition. Because of their chemical properties, contrast agents usually have a higher osmolality and are thicker (viscosity) than blood or cerebrospinal fluid. Therefore, osmolality and viscosity affect the safety of the contrast medium as they play a role in the development of contrast reactions. Furthermore, a number of adverse effects attributed to intravascular iodinated contrast agents appear to be related to osmolality. This includes allergic reactions, fluid shifts, physiological side effects, sensation of heat, and any complications resulting from contrast extravasation (Journal of Nuclear Medicine Technology, 2008). It has been noted that as osmolality increases, the risk of having an adverse reaction becomes more likely due to the high toxicity of the contrast medium. The toxicity of the contrast medium tends to decrease as the osmolality approaches that of blood serum, as observed in a non-ionic contrast, for example Omnipaque (ACR, 2013). Therefore, the lower the osmolality, the safer the contrast medium. Furthermore, as Chapman and Nakielny state, “Low- and iso-osmolar contrast agents are 5-10 times safer than high-osmolality contrast agents.” Similarly, there is considerable variation in the osmolality of contrast media and, therefore, how safe they are for the patient, depending on their ion...... middle of paper ......f contrast ( ACR, 2012). It is also essential that the radiologist performs a preliminary drug check before contrast administration. This involves checking the name, strength, dose administered, expiration date, batch number, color/appearance and seal on the bottle. If these aspects are not controlled properly, this could compromise the safety of the contrast media. In conclusion, it is clear that intravascular contrast agents are indispensable in the practice of radiology. Although contrast agents are widely used and have few side effects, reactions can occur, just as they do with any pharmaceutical product. However, these reactions are rare, so the benefit the contrast has on exams certainly outweighs the risk. Therefore, the use of intravascular contrast agents is safe in most patients and should not be ignored since a limited number of patients experience reactions to them.