Radiological Contrast Agents

An ideal contrast agent should have the following properties fa) ready availability and low cost fb) excellent x-n absorption characteristics at the x-ray eneigies used in diagnostic radiology (c) minimal toxicity and ready patient acceptance (d) chemical stability fe) high water solubility ilh low viscosity and no significant osmotic effects and ifi the ability to be administered for selective tissue uptake cod excretion. 

No compound has all ofthc.se characteristics. Barium sulfate and a variety of iodine compound.s. however, produce txcellem radiological contrast with low patient toxicity and xiatively low cost. The use of barium and iodine compounds Biadiological contrast agents is based on their radiographic ippearance and their distribution and elimination from the bedy. Contrast media are used in very large quantities and lie usually administered over a short time. 

Barium sulfate is a nearly ideal contrast agent for oral and rectal studies of the Cl tract. It produces a metal-like density gaiadiological studies, is readily available at low cost. and. xlwn used properly, has minimal patient morbidity and mor-alily. Many water-soluble barium compounds are quite iiric. but barium sulfate is an insoluble while power that is Imulaicd in water as a colloidal suspension. 

The majority of contrast agents used to opacify blood ves-tdv and increase contrast in solid organs such as the liver lie water-soluble organic iodides. Iodine absorbs x-rays cf-fttlively at many energy levels and produces a type of calcific or bone density on radiographic studies. Its den-sily. somewhat less than that of barium sulfate, is quite icctptable. 

Until the 1980s. most water-soluble conira.sl agents con-iuted of iriiodinated benzoic acid salts. In solution, they Jiua-iate into two particles, a iriiodinated anion and a cation. which consists of either a sodium or melhylglucamine 

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Lithium carbonate, administered for affective and bipolar disorders, may enhance the effects of antithyroid drugs. Potassium iodide, used as an expectorant, is a major ingredient in many cough medications. Iodide derived from this source may enhance the effects of antithyroid drugs and lead to iodine-induced hypothyroidism. Iodine in topical antiseptics and radiological contrast agents may act in a similar manner. 

Sheffield, United Kingdom Radiological contrast agents... 

Perflenapent (Sonus) EchoGen 1) Gardiology contrast agent. 2) Radiology contrast agent. liquid at room temperature 4.40 (experimental)... 

An example of a drug that is known to cause type 1 allergic reactions is penicillin. Radiological contrast agents can also provoke this type of allergic reaction. 

Radiological contrast agents are among the most commonly used iodine-containing drugs. Others are iodine-containing antiseptics and expectorants.)... 

Other drugs that are useful in the rapid treatment of the severely thyrotoxic patient are agents that inhibit the peripheral conversion of thyroxine to triiodothyronine. Dexamethasone (0.5 to 1 mg two to four times daily), and the iodinated radiological contrast agents iopanoic acid (Telepaque, 500 to 1000 mg once daily), and sodium ipodate (Qragrafin, 500 to 1000 mg once daily) are effective in preoperative preparation. Neither iopanoic acid nor sodium ipodate is available in the United States. Cholestyramine has been used in severely toxic patients to bind thyroid hormones in the gut and thus block the enterohepatic circulation of the iodothyronines. 

Many highly water-soluble radiological contrast agents are solubilized as sugar conjugates. This is the case for... 

Radiological contrast agents are used to obtain added information, both anatomical and functional, from an imaging examination. 

TABLE 4 Risks 46. RADIOLOGICAL CONTRAST AGENTS AND RADIOPHARMACEUTICALS of Systemic Fibrosis from Gadolinium-Containing Salts ... 

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