Usage
Iopamidol is a non-ionic, water-soluble, iodinated radiographic contrast medium. It is used to enhance the visibility of internal organs and structures during radiographic procedures like X-rays, computed tomography (CT) scans, and angiography.
It is indicated for:
- Intra-arterial procedures: Peripheral arteriography, visceral arteriography, aortography, and coronary arteriography (including left ventriculography).
- Intravenous procedures: Excretory urography, intravenous digital subtraction angiography, contrast enhancement for computed tomography (head and body), and peripheral venography (phlebography).
- Intrathecal procedures: Lumbar, thoracic, and cervical myelography (using a specific formulation).
Pharmacological Classification: Radiographic contrast agent.
Mechanism of Action: Iopamidol works by absorbing X-rays to a greater degree than surrounding tissues. This creates a contrast that allows visualization of blood vessels, organs, and other structures.
Alternate Names
Iopamidol is the generic name. Brand names include Isovue®, Isovue-M®, and others. International or regional variations of the name may exist.
How It Works
Pharmacodynamics: Iopamidol exerts its effect solely through its ability to absorb X-rays, enhancing radiographic contrast. It has no direct pharmacological activity on the body.
Pharmacokinetics:
- Absorption: After intravascular administration, iopamidol distributes rapidly into the extracellular fluid. It does not bind to plasma proteins. For intrathecal use, the distribution is within the cerebrospinal fluid.
- Metabolism: Iopamidol is not metabolized.
- Elimination: It is primarily excreted unchanged by the kidneys via glomerular filtration. A small portion may be excreted hepatically in patients with renal impairment.
Mode of Action: Iopamidol’s mode of action relies on its high iodine content. Iodine atoms within the iopamidol molecule effectively absorb X-ray photons, resulting in increased radiopacity of the contrast-filled structure compared to surrounding tissues. There is no receptor binding, enzyme inhibition, or neurotransmitter modulation involved.
Elimination pathways: Primarily renal excretion. Hepatic excretion may play a minor role, particularly in individuals with compromised renal function.
Dosage
Iopamidol dosage is dependent on the specific procedure, patient age, weight, and renal function. Always refer to the specific product labeling.
Standard Dosage
Children: Pediatric doses are generally based on weight (mL/kg) using concentrations similar to adults. Refer to product-specific pediatric dosing charts.
Special Cases:
- Elderly Patients: Exercise caution due to potential age-related decline in renal function. Lower doses and careful monitoring are advised.
- Patients with Renal Impairment: Dose adjustments are required, and the benefit-risk ratio should be carefully evaluated.
- Patients with Hepatic Dysfunction: Close monitoring is required as hepatic excretion may become more significant.
- Patients with Comorbid Conditions: Assess the potential risks in patients with conditions like diabetes, cardiovascular disease, and thyroid disorders.
Clinical Use Cases
Dosage recommendations are highly variable and specific to the clinical setting and procedure. Always consult the product information for precise guidance.
Dosage Adjustments
Adjustments are necessary for renal/hepatic impairment, and individualization is essential. Consider factors like creatinine clearance, liver function tests, and co-existing medical conditions.
Side Effects
Common Side Effects
Nausea, vomiting, warmth or flushing, headache, pain at the injection site, metallic taste.
Rare but Serious Side Effects
Severe allergic reactions (anaphylaxis), renal failure, seizures, cardiac arrhythmias, stroke.
Long-Term Effects
Generally, there are no long-term side effects associated with a single administration of Iopamidol. However, repeated exposure to high doses of iodine can affect thyroid function.
Adverse Drug Reactions (ADR)
Severe allergic reactions, nephrotoxicity, thyroid dysfunction, neurotoxicity, cardiovascular events.
Contraindications
Hypersensitivity to iopamidol, severe combined hepatic and renal impairment, intrathecal use with corticosteroids, active thyroid storm.
Drug Interactions
Interferes with thyroid function tests for up to 16 days. May increase risk of renal toxicity with metformin. Caution is advised in patients receiving interleukin-2.
Pregnancy and Breastfeeding
- Pregnancy: Pregnancy Category B. Use only if clearly needed, weighing the potential benefits against the risks.
- Breastfeeding: Iodinated contrast agents are excreted in breast milk. A lactating woman may choose to pump and discard breast milk for up to 10 hours after administration.
Drug Profile Summary
- Mechanism of Action: X-ray absorption enhancing radiographic contrast.
- Side Effects: Nausea, vomiting, warmth, metallic taste (common); allergic reactions, renal failure, seizures (serious).
- Contraindications: Hypersensitivity, severe combined hepatic/renal impairment.
- Drug Interactions: Interferes with thyroid function tests, potential renal toxicity with metformin.
- Pregnancy & Breastfeeding: Use with caution; consult product labeling.
- Dosage: Highly variable; consult product labeling for specific procedures and patient factors.
- Monitoring Parameters: Renal function, thyroid function (especially in infants and young children), vital signs.
Popular Combinations
Iopamidol is typically used alone but can be used in conjunction with other imaging agents or medications related to the specific procedure.
Precautions
-
General Precautions: Screen for allergies, assess renal and hepatic function, thyroid status, and comorbid conditions. Maintain adequate hydration before and after administration. Always have emergency resuscitation equipment available.
-
Specific Populations: Consult product labeling for specific precautions in pregnant women, breastfeeding mothers, children, and the elderly.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Iopamidol?
A: The dosage of Iopamidol varies widely depending on the procedure and patient factors. Always refer to the specific product labeling.
Q2: What are the common side effects?
A: Common side effects include nausea, vomiting, a feeling of warmth or flushing, headache, and pain at the injection site.
Q3: What are the serious side effects?
A: Serious side effects include allergic reactions (anaphylaxis), renal failure, seizures, cardiac arrhythmias, and thyroid dysfunction.
Q4: Can Iopamidol be used in pregnant or breastfeeding women?
A: It should be used with caution. Consult the product labeling and weigh the risks versus benefits. Breastfeeding mothers may choose to interrupt breastfeeding for a short period.
Q5: How is Iopamidol eliminated from the body?
A: Primarily through renal excretion.
Q6: What are the contraindications for using Iopamidol?
A: Contraindications include hypersensitivity to the drug and severe combined hepatic and renal impairment.
Q7: Does Iopamidol interact with other medications?
A: It can interfere with thyroid function tests. Caution should be exercised when using it with metformin.
Q8: What precautions should be taken before administering Iopamidol?
A: Assess renal and hepatic function, screen for allergies, and ensure adequate hydration.
Q9: What is the mechanism of action of Iopamidol?
A: It works by absorbing X-rays, increasing the contrast between tissues and structures during radiographic procedures.
