Gadoxetate

Gadoxetate, also known as gadoxetate disodium, is a gadolinium-based contrast agent (GBCA) used in magnetic resonance imaging (MRI) to enhance the quality of the images. It is marketed under the trade names Eovist in the United States and Primovist in other regions. Gadoxetate is particularly used for liver imaging due to its unique properties that allow for both vascular and hepatocyte-specific imaging.

Chemical Properties

Gadoxetate is a complex of gadolinium with the ligand ethoxybenzyl-diethylenetriamine pentaacetic acid (EOB-DTPA). The chemical formula is C23H28GdN3O11, and it has a molecular weight of 725.7 g/mol. The gadolinium ion is tightly bound within the chelate, reducing the risk of gadolinium toxicity.

Mechanism of Action

Gadoxetate functions by altering the local magnetic field in tissues where it accumulates, thereby enhancing the contrast of the MRI images. It is a paramagnetic agent, which means it has unpaired electrons that enhance the relaxation rates of nearby hydrogen nuclei, leading to increased signal intensity on T1-weighted MRI images.

Pharmacokinetics

After intravenous administration, gadoxetate is distributed in the extracellular fluid. Approximately 50% of the dose is taken up by hepatocytes and excreted into the bile, while the remaining 50% is excreted by the kidneys. The elimination half-life of gadoxetate is approximately 0.9 hours in patients with normal renal function.

Clinical Uses

Gadoxetate is primarily used for liver imaging in MRI. It is particularly useful for detecting and characterizing focal liver lesions, such as hepatocellular carcinoma, metastases, and benign liver tumors. The agent provides both dynamic imaging during the arterial and portal venous phases and delayed imaging during the hepatobiliary phase, which occurs approximately 20 minutes after injection.

Safety and Adverse Effects

Gadoxetate is generally well-tolerated, but like all GBCAs, it carries a risk of nephrogenic systemic fibrosis (NSF) in patients with severe renal impairment. Common side effects include nausea, headache, and dizziness. Rarely, allergic reactions may occur.

Contraindications

Gadoxetate is contraindicated in patients with known hypersensitivity to gadolinium-based contrast agents. Caution is advised in patients with severe renal impairment due to the risk of NSF.

Special Populations

Pregnancy

Gadoxetate is classified as a pregnancy category C drug in the United States, indicating that risk to the fetus cannot be ruled out. It should only be used during pregnancy if the potential benefit justifies the potential risk.

Pediatric Use

The safety and effectiveness of gadoxetate in pediatric patients have not been established. Use in children should be considered carefully, weighing the potential benefits and risks.

Conclusion

Gadoxetate is a valuable tool in the diagnostic imaging of liver diseases, offering both vascular and hepatocyte-specific imaging capabilities. Its use should be carefully considered in patients with renal impairment and during pregnancy.

See Also

• Gadolinium-based contrast agent
• Magnetic resonance imaging
• Hepatocellular carcinoma