Usage
Iohexol is a non-ionic, water-soluble, iodinated radiographic contrast medium. It is used to enhance the visibility of internal organs and structures during various X-ray and computed tomography (CT) imaging procedures.
Pharmacological Classification: Radiographic contrast agent.
Mechanism of Action: Iohexol does not have a pharmacological effect on the body. Its mechanism of action is based on its high iodine content, which absorbs X-rays and enhances the contrast between tissues or structures being examined and the surrounding areas, enabling clearer visualization.
Alternate Names
Iohexol is known internationally by the same generic name. It is frequently marketed under the brand name OMNIPAQUE. Other brand names might exist regionally.
How It Works
Pharmacodynamics: Iohexol is inert and does not have any direct pharmacological effects on the body’s tissues.
Pharmacokinetics:
- Absorption: Following intravenous administration, iohexol is rapidly distributed in the extracellular fluid. It does not cross the blood-brain barrier in intact central nervous systems. After oral or rectal administration for GI studies, absorption is minimal.
- Metabolism: Iohexol is not metabolized.
- Elimination: It is primarily excreted unchanged by the kidneys via glomerular filtration, with near-complete elimination within 24 hours in patients with normal renal function. Elimination may be delayed in patients with renal impairment.
Mode of Action: The iodine in iohexol absorbs X-rays, creating enhanced contrast on radiographic images. There is no receptor binding, enzyme inhibition, or neurotransmitter modulation involved.
Dosage
Iohexol dosage varies greatly depending on the specific procedure, patient age, weight, and renal function. Always refer to product-specific guidelines and consider patient factors.
Standard Dosage
Adults:
Dosing depends on the procedure. Examples:
- Intravenous Urography: 200-350 mgI/kg body weight.
- Angiography: varies depending on the vessel being studied.
- CT: varies depending on the organ being imaged.
Children:
Dosing is usually based on weight, typically lower than adult doses. Consult pediatric dosing guidelines for specifics based on the procedure.
Special Cases:
- Elderly Patients: Start at the lower end of the dosing range due to potential age-related decreased organ function.
- Patients with Renal Impairment: Dose reduction or alternative imaging methods may be necessary.
- Patients with Hepatic Dysfunction: Caution advised; dose adjustment may be required.
- Patients with Comorbid Conditions: Consider the impact of coexisting medical conditions on dosing.
Clinical Use Cases
The dosage in these settings should be individualized according to the specific protocol for the procedure.
- Intubation: Not applicable.
- Surgical Procedures: Intraoperative angiography may utilize iohexol, with dosing dependent on the procedure.
- Mechanical Ventilation: Not applicable.
- Intensive Care Unit (ICU) Use: Dose adjustments based on patient hemodynamics and renal function.
- Emergency Situations: Dose optimization is crucial, considering potential hemodynamic instability and renal compromise.
Dosage Adjustments
Modifications are necessary for patients with renal or hepatic impairment, and other medical conditions. Always individualize the dose based on patient characteristics and consult product-specific guidelines.
Side Effects
Common Side Effects:
- Headache
- Nausea
- Vomiting
- Pain at injection site
- Warmth or flushing sensation
- Altered taste (metallic)
Rare but Serious Side Effects:
- Severe allergic reactions (anaphylaxis)
- Renal failure
- Seizures
- Cardiac arrhythmias
- Thyroid storm (in patients with hyperthyroidism)
Long-Term Effects:
Generally, iohexol doesn’t cause long-term side effects, as it is excreted quickly. However, rare cases of delayed reactions like nephropathy have been reported.
Adverse Drug Reactions (ADR):
Severe ADRs like anaphylaxis, renal failure, and cardiac events require immediate medical intervention.
Contraindications
- Known hypersensitivity to iohexol or its components.
- Severe thyrotoxicosis.
- Manifest or latent decompensated cardiac failure.
- Severe renal insufficiency.
- Myelography in active infections or bleeding disorders.
- Concurrent intrathecal corticosteroid administration.
Drug Interactions
- Metformin: Increased risk of lactic acidosis. Discontinue metformin pre-procedure and re-evaluate renal function before restarting.
- Radioactive Iodine: May interfere with thyroid uptake and decrease efficacy of radioactive iodine therapy.
- Interleukin-2: Increased risk of hypersensitivity reactions.
- Other nephrotoxic drugs: May increase risk of renal impairment.
Pregnancy and Breastfeeding
- Pregnancy: Iohexol crosses the placenta. Use only if clearly needed. Hysterosalpingography is contraindicated in pregnancy.
- Breastfeeding: Small amounts are excreted in breast milk. Breastfeeding may be continued, though some recommend temporary interruption.
Drug Profile Summary
- Mechanism of Action: Provides radiographic contrast by absorbing X-rays.
- Side Effects: Headache, nausea, vomiting, pain at injection site, allergic reactions (rarely severe).
- Contraindications: Hypersensitivity, thyrotoxicosis, decompensated cardiac failure, severe renal insufficiency.
- Drug Interactions: Metformin, radioactive iodine.
- Pregnancy & Breastfeeding: Use with caution in pregnancy; breastfeeding generally considered safe.
- Dosage: Varies widely depending on procedure and patient factors.
- Monitoring Parameters: Renal function, vital signs, allergic reactions.
Popular Combinations
Iohexol is typically used alone but might be combined with other agents during specific procedures (e.g., saline flush).
Precautions
- Evaluate renal function, especially in high-risk patients.
- Ensure adequate hydration.
- Have emergency equipment and personnel available for managing potential reactions.
- Exercise caution in patients with a history of allergies or asthma.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Iohexol?
A: The dosage varies greatly depending on the procedure, patient age and weight, and renal function. Refer to specific product information and imaging protocols.
Q2: What are the common side effects?
A: Common side effects include headache, nausea, vomiting, pain at injection site, warmth, and altered taste.
Q3: What are the contraindications?
A: Contraindications include hypersensitivity, thyrotoxicosis, cardiac decompensation, severe renal failure, myelography in active infections/bleeding, and concurrent intrathecal corticosteroids.
Q4: How is Iohexol eliminated from the body?
A: Primarily excreted unchanged by the kidneys.
Q5: How should I manage a patient with a history of allergic reactions to contrast media?
A: Premedication with corticosteroids and antihistamines may be considered. Close monitoring is essential.
Q6: Can Iohexol be used in pregnant or breastfeeding women?
A: Use cautiously during pregnancy if absolutely necessary. Hysterosalpingography is contraindicated. Breastfeeding may be continued with minimal risk.
Q7: How does renal impairment affect the dosage of Iohexol?
A: Dose reduction or alternative imaging methods may be necessary in patients with renal impairment. Careful assessment of renal function is crucial.
Q8: What should I do if a patient experiences a severe allergic reaction?
A: Stop administration immediately and provide supportive care (e.g., epinephrine, oxygen). Closely monitor vital signs.
Q9: Can iohexol be administered intrathecally?
A: Yes, specific formulations are available for intrathecal use, such as in myelography.
