Contrast media (sing. medium) (CM)
Chemical substances, containing chemically bound iodine, used to highlight tissues and organs that are not distinguished from their surroundings on plain X-ray pictures. Usually injected with a needle into an arm vein, or directly into an artery via a catheter inserted into an artery in the groin and moved to the target organ/tissue. Other types of contrast media are based on barium, and are used to highlight the stomach and/or gut, and can either be swallowed or given as an enema. Contrast media are also used in MRI, but most of these are based on a metal called gadolinium Ideally a contrast medium should not have any effects at all except the physical ability to influence the diagnostic technique, in the case of X-ray contrast media the ability to absorb X-rays. All pharmacological effects are unwanted and they are expressions of toxic effects. Toxic effects of contrast media may be divided into osmotoxic effects and chemotoxic effects. Chemotoxicity is related to the toxicity of the molecule and may be linked to high binding of plasma protein, high tendency to release histamine, inhibition of biological functions like coagulation etc. Most frequently, high chemotoxicity will clinically show itself as a high incidence of nausea and vomiting. CM are also called contrast agents.
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