Indications for use and efficacy are similar to the other agents 4. It is a low osmolar, non-ionic contrast as is gadodiamide. Gadoteridol (Prohance, Squibb) was the third intravenous contrast agent on the market. No abnormal serum bilirubin levels occur, however elevated serum iron levels occurred with an incidence of 8.2% in one study of 73 patients.The efficacy of this contrast is similar to that of Gd-DTPA 3. It has a median lethal dose of 34 mmol/kg resulting in a safety ratio of 2-3 times that of Gd-DOTA, and 3-4 times that of Gd-DTPA. Gadodiamide (Omniscan, Winthrop Pharm.) is a non-ionic complex with two-fifths of the osmolality of Gd-DTPA. Ionic chelates are also hyperosmolar and some of their side effects may be attributed to this property. The development of non-ionic contrast agents for MRI has paralleled that for iodinated contrast materials.
It is distributed in the intravascular and extracellular fluid spaces, does not cross an intact blood-brain-barrier, and is excreted rapidly by glomerular filtration 2. Magnetic Resonance Angiography MRA to evaluate adults with known or suspected renal or aorto-ilio-femoral occlusive vascular disease.
Gd-DTPA has similar pharmacokinetics as iodinated contrast agents. MRI of the central nervous system in adults and children over 2 years old to visualize lesions with abnormal Blood Brain Barrier BBB, or abnormal vascularity of the brain, spine, abd associated tissues. This large magnetic moment is related to its seven unpaired orbital electrons. Gd has a large magnetic moment, exceeded only by Dysprosium(III) and Holmium(III), explaining its paramagnetic properties at low concentrations. Although MRI was initially hoped to provide a means of making definitive diagnoses without administering contrast media, it has been found that the addition of contrast agents in many cases improves sensitivity and/or specificity. Gd-DTPA was the first intravenous MR contrast agent to be approved for human use ( Magnevist, Berlex Labs). MRI contrast agents have become an indispensable part of contemporary magnetic resonance imaging. Chelates with a higher stability constant have since been used successfully such as Gd-DTPA. Chelates of paramagnetic ions Cr and Gd with EDTA were first used however EDTA was of relatively low stability resulting in toxicity in animals 1.
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