Barium is a soft, silvery metal that rapidly tarnishes in air and reacts with water. Barium is not an extensively used element. Most is used in drilling fluids for oil and gas wells. It is also used in paint and in glassmaking. All barium compounds are toxic; however, barium sulfate is insoluble and so can be safely swallowed. A suspension of barium sulfate is sometimes given to patients suffering from digestive disorders. This is a ‘barium meal’ or ‘barium enema’. Barium is a heavy element and scatters X-rays, so as it passes through the body the stomach and intestines can be distinguished on an X-ray. Barium carbonate has been used in the past as a rat poison. Barium nitrate gives fireworks a green colour. Barium has no known biological role, although barium sulfate has been found in one particular type of algae. Barium is toxic, as are its water- or acid-soluble compounds. This drug is used as a contrast agent in diagnostic x-ray procedures. Therapeutic advantages of barium sulfate in diagnostic procedures include both its low water solubility and high level of clearance from the body. Barium sulfate is ingested by mouth or administered rectally and combined with granules of effervescent bicarbonate to enhance distension of the GI tract, allowing for enhanced gastrointestinal tract visualization. Barium (E-Z-CAT DRY) is a radiographic contrast agent indicated for use in computed tomography (CT) of the abdomen to delineate the gastrointestinal (GI) tract in adult and pediatric patients. Under physiological conditions, barium sulfate passes through the GI tract in an unchanged form and is absorbed only in pharmacologically insignificant amounts. Common adverse reactions include nausea, vomiting, diarrhea and abdominal cramping.