Usage
Gadodiamide is a gadolinium-based contrast agent (GBCA) used to enhance the clarity of magnetic resonance imaging (MRI) scans. It is administered intravenously before an MRI to aid in the diagnosis of various medical conditions affecting the central nervous system (CNS), such as brain and spinal cord tumors, as well as conditions affecting other body areas like the chest, abdomen, pelvis, and musculoskeletal system. It facilitates the visualization of lesions with abnormal vascularity or those causing disruptions in the blood-brain barrier. Gadodiamide’s pharmacological classification is as a contrast agent. Its mechanism of action involves shortening the T1 relaxation time of water protons in tissues, resulting in increased signal intensity and improved contrast in MRI images.
Alternate Names
Gadodiamide is also known by its brand name, Omniscan.
How It Works
Pharmacodynamics: Gadodiamide exerts its effect by influencing the magnetic properties of water molecules within the body. It shortens the T1 relaxation time of water protons in the vicinity of gadolinium ions, leading to enhanced signal intensity on T1-weighted MRI images. This improved contrast allows for better visualization of tissues and structures, particularly those with abnormal vascularity or blood-brain barrier disruption.
Pharmacokinetics: After intravenous administration, gadodiamide is rapidly distributed in the extracellular fluid space, with a volume of distribution comparable to that of extracellular water. It exhibits a biphasic elimination profile, with an initial distribution half-life of approximately 4 minutes and a terminal elimination half-life of about 70 minutes. Gadodiamide is primarily excreted unchanged through the kidneys by glomerular filtration. Around 85% of the administered dose appears in the urine within 4 hours, reaching 95-98% within 24 hours. Minimal metabolism occurs.
Mode of action: Gadolinium ions, being paramagnetic, interact with surrounding water protons, accelerating their T1 relaxation. This mechanism amplifies the signal difference between tissues on MRI scans, thereby augmenting the contrast.
Receptor binding, enzyme inhibition, or neurotransmitter modulation: Gadodiamide does not bind to receptors, inhibit enzymes, or modulate neurotransmitters. Its action is purely physical, based on its paramagnetic properties.
Elimination pathways: The predominant elimination route is renal excretion, via glomerular filtration.
Dosage
Standard Dosage
Adults:
The standard dose for CNS imaging is 0.1 mmol/kg (equivalent to 0.2 mL/kg) administered as a rapid intravenous bolus injection. For body imaging, the recommended dose is 0.2 to 0.3 mmol/kg (0.4 to 0.6 ml/kg), also given intravenously. The intravenous line should be flushed with saline following administration to ensure complete delivery.
Children (2 years and older):
The pediatric dose for CNS imaging is 0.1 mmol/kg (0.2 mL/kg) given intravenously. For body imaging, similar to adults, the dose ranges from 0.1 to 0.2 mmol/kg (0.2 to 0.4 mL/kg) intravenously.
Special Cases:
- Elderly Patients: Although no specific dose adjustments are recommended based on age, caution is advised due to the potential for reduced renal function in elderly individuals. Renal function testing (e.g., eGFR) is recommended prior to administration.
- Patients with Renal Impairment: Gadodiamide is contraindicated in patients with severe renal impairment (GFR < 30 mL/min/1.73m²) or acute kidney injury. For patients with moderate renal impairment, the dose should be minimized and renal function closely monitored.
- Patients with Hepatic Dysfunction: No dose adjustments are necessary in patients with hepatic impairment.
- Patients with Comorbid Conditions: Use with caution in patients with a history of allergic reactions.
Clinical Use Cases
The dosage guidelines provided under “Standard Dosage” apply across various clinical scenarios, including intubation, surgical procedures, mechanical ventilation, ICU use, and emergency situations. There are no specific dosage recommendations for these settings beyond the standard guidelines.
Dosage Adjustments
Dose modifications are primarily necessary in patients with renal impairment, as outlined above.
Side Effects
Common Side Effects:
Nausea, headache, dizziness, pain or discomfort at the injection site, coldness, a metallic taste, and localized warmth or burning sensation.
Rare but Serious Side Effects:
Nephrogenic systemic fibrosis (NSF) (in patients with renal impairment), severe allergic reactions (anaphylaxis), acute kidney injury, seizures, and changes in consciousness.
Long-Term Effects:
Gadolinium deposition in various organs, including the brain, has been reported. The long-term clinical significance of this deposition remains unclear.
Adverse Drug Reactions (ADR):
Severe allergic reactions (including anaphylaxis and bronchospasm), NSF, and acute kidney injury require immediate intervention.
Contraindications
- Severe renal impairment (GFR < 30 mL/min/1.73m²) or acute kidney injury
- History of hypersensitivity to gadodiamide or other GBCAs
- Neonates up to 4 weeks of age (due to immature renal function)
Drug Interactions
No specific drug interactions are known, but it can interfere with serum calcium and iron levels, potentially affecting results of certain laboratory tests. Inform laboratory personnel about recent gadodiamide administration.
Pregnancy and Breastfeeding
Gadodiamide is pregnancy category C. Animal studies have shown some evidence of fetal risk. It is not recommended during pregnancy unless the benefits clearly outweigh the risks. The drug can pass into breast milk, but the amount is small. While generally considered safe, breastfeeding interruption for 24 hours post-administration may be considered, especially for newborns or preterm infants. Discuss with the patient and weigh the risks and benefits.
Drug Profile Summary
- Mechanism of Action: Shortens T1 relaxation times, enhancing MRI signal intensity.
- Side Effects: Nausea, headache, injection site reactions; rarely, NSF, allergic reactions, kidney injury.
- Contraindications: Severe renal impairment, acute kidney injury, hypersensitivity to GBCAs.
- Drug Interactions: No significant drug interactions known.
- Pregnancy & Breastfeeding: Category C; use with caution; breastfeeding generally safe.
- Dosage: 0.1 mmol/kg for CNS; 0.2-0.3 mmol/kg for body imaging; IV administration.
- Monitoring Parameters: Renal function (eGFR) in patients with renal impairment.
Popular Combinations
Gadodiamide is generally used alone. No popular drug combinations are associated with its clinical use.
Precautions
- Screen all patients for renal dysfunction.
- Avoid intrathecal administration.
- Exercise caution in patients with a history of allergies or other hypersensitivity disorders.
- Monitor for signs of NSF in patients with pre-existing renal conditions.
- Minimize dose in patients with moderate renal impairment.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Gadodiamide?
A: 0.1 mmol/kg intravenously for CNS imaging; 0.2-0.3 mmol/kg intravenously for body imaging. Pediatric dose (2 years and older) is similar.
Q2: What are the common side effects?
A: Nausea, headache, dizziness, injection site reactions (pain, coldness, warmth).
Q3: Is Gadodiamide safe for patients with kidney disease?
A: No. Gadodiamide is contraindicated in patients with severe renal impairment or acute kidney injury. Use with caution and minimize the dose in moderate renal impairment.
Q4: What is Nephrogenic Systemic Fibrosis (NSF)?
A: A rare but serious condition characterized by fibrosis of skin, muscle, and internal organs. GBCA exposure, including gadodiamide, is a risk factor in patients with impaired renal function.
Q5: Can Gadodiamide be used in pregnant women?
A: Only if absolutely necessary and the benefits outweigh the risks. It’s a pregnancy category C drug.
Q6: Can Gadodiamide be used in breastfeeding mothers?
A: Generally safe. Temporary cessation of breastfeeding (24 hours) may be an option, particularly for newborns or preterm infants. Discuss with the patient and consider the risks and benefits.
Q7: How is Gadodiamide administered?
A: As a bolus intravenous injection. Flush the IV line with saline to ensure complete administration.
Q8: What are the main contraindications?
A: Severe renal impairment, acute kidney injury, and hypersensitivity to gadodiamide or other GBCAs.
Q9: Does Gadodiamide interact with any other medications?
A: No clinically significant drug interactions are known. However, it may interfere with serum calcium and iron measurements.
Q10: What is the mechanism of action of Gadodiamide?
A: It shortens the T1 relaxation time of water protons, increasing signal intensity in MRI images.
