Usage
Gadopentetic acid is a gadolinium-based contrast agent (GBCA) used in magnetic resonance imaging (MRI) to enhance the visualization of internal organs, blood vessels, and tissues. It is particularly useful for imaging the central nervous system (brain and spinal cord) and for identifying areas of inflammation or tumors. Its pharmacological classification is diagnostic agent, MRI contrast medium. Gadopentetic acid works by shortening the T1 relaxation time of water protons within the body, leading to increased signal intensity and improved image clarity in MRI scans.
Alternate Names
- Gadopentetate dimeglumine
- Dimeglumine gadopentetate
- Gd-DTPA (chemical abbreviation)
Brand names:
- Magnevist
- Magnegita
- Magnetol
- Emaray
How It Works
Pharmacodynamics: Gadopentetic acid is a paramagnetic compound. The gadolinium ion (Gd3+) has seven unpaired electrons, creating a strong magnetic field that interacts with nearby water protons. This interaction shortens the T1 relaxation time of the water protons, increasing the signal intensity in T1-weighted MRI images. The areas where gadopentetic acid accumulates appear brighter on the scan.
Pharmacokinetics: Following intravenous administration, gadopentetic acid is rapidly distributed into the extracellular fluid. It does not cross the blood-brain barrier in normal circumstances, but may do so in areas with disrupted barrier integrity (e.g., tumors). It is primarily eliminated through renal excretion (glomerular filtration) with a plasma half-life of approximately 1.6 hours. A small amount (<0.04%) may be excreted in breast milk after intravenous administration. It is poorly absorbed orally.
Mode of Action/Receptor Binding/Enzyme Inhibition/Neurotransmitter Modulation: Gadopentetic acid’s mechanism of action is purely physical, based on its paramagnetic properties. It does not bind to receptors, inhibit enzymes, or modulate neurotransmitters.
Elimination Pathways: Renal excretion is the primary route of elimination, with approximately 90% of the dose eliminated unchanged in the urine within 24 hours.
Dosage
Standard Dosage
Adults:
The standard dose is 0.1 mmol/kg (0.2 mL/kg) administered as an intravenous bolus injection, at a rate not exceeding 10 mL/15 seconds. A second dose of 0.1-0.2 mmol/kg may be administered within 30 minutes if needed. The maximum dose is 0.3 mmol/kg.
Children:
For children older than one month, including term neonates, the recommended dose is 0.1 mmol/kg (0.2 mL/kg) by intravenous bolus injection. For children older than one year, a second dose of 0.1-0.2 mmol/kg can be given after 30 minutes if necessary. No data is available for neonates less than 4 weeks old (usage is contraindicated in this population).
Special Cases:
- Elderly Patients: No dose adjustment is generally necessary but caution should be exercised.
- Patients with Renal Impairment: Contraindicated in severe renal impairment (GFR < 30 mL/min/1.73 m2). Caution should be exercised in mild to moderate renal impairment.
- Patients with Hepatic Dysfunction: No dosage adjustments are provided in the manufacturer’s labeling for moderate hepatic impairment. Data on patients with severe hepatic impairment are not available.
- Patients with Comorbid Conditions: Caution is advised in patients with a history of allergic reactions, asthma, seizure disorders, or intracranial lesions.
Clinical Use Cases
Gadopentetic acid may be used for contrast-enhanced MRI in various clinical settings, including:
- CNS imaging (brain and spinal cord): For visualizing tumors, infections, inflammation, and other abnormalities.
- Vascular imaging: For visualizing blood vessels and identifying areas of stenosis or occlusion.
- Whole-body imaging: For detecting tumors and other abnormalities in various organs.
- Arthrography: Intra-articular injection for imaging joints.
The standard dosage applies for these use cases.
Dosage Adjustments
Dose adjustments may be required in certain patient populations:
- Renal/Hepatic dysfunction: As described in “Special Cases.”
- Metabolic disorders and genetic polymorphisms: Consult product information regarding specific metabolic or genetic factors affecting drug metabolism.
Side Effects
Common Side Effects:
- Nausea
- Vomiting
- Headache
- Dizziness
- Injection site reactions (pain, swelling, irritation)
- Hot or cold sensation
- Altered taste (dysgeusia)
Rare but Serious Side Effects:
- Nephrogenic systemic fibrosis (NSF) in patients with renal dysfunction.
- Hypersensitivity reactions (including anaphylaxis)
- Seizures (rare)
Long-Term Effects:
- Gadolinium retention in various tissues including the brain, bones, and skin. The long-term health effects of gadolinium deposition are still not fully understood.
Adverse Drug Reactions (ADR):
- Anaphylaxis: Requires immediate medical intervention.
- NSF: Requires immediate discontinuation of the drug and supportive care.
Contraindications
- Hypersensitivity to gadopentetic acid or any of its components.
- Severe renal impairment (GFR < 30 mL/min/1.73 m2).
- Patients in the perioperative liver transplantation period.
- Neonates younger than 4 weeks of age.
Drug Interactions
- No formal drug interaction studies have been conducted.
- Iodinated contrast media reduce the contrast achievable with gadopentetic acid and should not be administered together.
- Consult drug interaction databases for other potential drug interactions.
Pregnancy and Breastfeeding
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Pregnancy: Gadolinium crosses the placenta. Data on gadolinium use in pregnancy is limited. Use only if clearly needed and the benefits outweigh the risks. Pregnancy category C.
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Breastfeeding: Minimal amounts are excreted in breast milk. While generally considered safe, discuss the risks and benefits with the mother. Consider interrupting breastfeeding for 24 hours after administration.
Drug Profile Summary
- Mechanism of Action: Shortens T1 relaxation time of water protons, enhancing MRI image contrast.
- Side Effects: Nausea, vomiting, headache, injection site reactions, NSF (rare but serious).
- Contraindications: Severe renal impairment, hypersensitivity, neonates <4 weeks old, perioperative liver transplant.
- Drug Interactions: Iodinated contrast media. Consult drug interaction databases for additional interactions.
- Pregnancy & Breastfeeding: Use with caution. Discuss risks and benefits with the patient.
- Dosage: 0.1 mmol/kg IV, may be repeated once. Maximum 0.3 mmol/kg.
- Monitoring Parameters: Renal function (prior to administration), signs of hypersensitivity, injection site.
Popular Combinations
No specific drug combinations are typically used with gadopentetic acid for enhancing MRI images.
Precautions
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General Precautions: Assess renal function prior to administration. Monitor for hypersensitivity reactions during and after the procedure.
-
Specific Populations: See “Dosage - Special Cases” and “Pregnancy and Breastfeeding”.
FAQs
Q1: What is the recommended dosage for Gadopentetic Acid?
A: 0.1 mmol/kg (0.2 mL/kg) intravenously for adults and children >1 month. Maximum dose 0.3 mmol/kg.
Q2: Is Gadopentetic Acid safe for patients with kidney problems?
A: No. Contraindicated in severe renal impairment (GFR < 30 mL/min/1.73 m2). Caution is advised in mild to moderate renal impairment.
Q3: Can Gadopentetic Acid be used in pregnant women?
A: Use with caution only if the benefits outweigh the potential risks. Gadolinium crosses the placenta, and the safety for the fetus is not fully established.
Q4: What are the common side effects of Gadopentetic Acid?
A: Nausea, headache, vomiting, dizziness, and injection site reactions.
Q5: Are there any long-term risks associated with Gadopentetic Acid?
A: Gadolinium deposition in tissues, including the brain, has been observed. The long-term clinical significance of this is still under investigation.
Q6: How is Gadopentetic Acid eliminated from the body?
A: Primarily through renal excretion.
Q7: Can Gadopentetic Acid be used in children?
A: Yes, for children older than one month, using the same dose as adults (0.1 mmol/kg). Contraindicated in neonates <4 weeks old.
Q8: What is the mechanism of action of Gadopentetic Acid?
A: It shortens the T1 relaxation time of water protons, increasing signal intensity on T1-weighted MRI images.
Q9: Is Gadopentetic Acid safe for breastfeeding mothers?
A: Minimal amounts are excreted in breast milk. While generally considered safe, interrupting breastfeeding for 24 hours can be considered. Discuss risks and benefits with the patient.
Q10: Can Gadopentetic acid be mixed with other contrast agents?
A: It should not be mixed with iodinated contrast media, as this reduces its effectiveness.
