Introduction
Iopamidol is a non-ionic, low-osmolar contrast medium used primarily for radiographic imaging procedures. As a water-soluble iodinated contrast agent, it enhances visualization of vascular structures and body cavities during various diagnostic procedures including computed tomography (CT), angiography, and urography. Developed to improve safety profile compared to earlier ionic contrast media, iopamidol has become a widely used diagnostic agent in clinical practice.
Mechanism of Action
Iopamidol works through its high iodine content (approximately 49% by weight), which attenuates X-rays passing through the body. When administered, it creates a density difference between anatomical structures and surrounding tissues, allowing enhanced visualization on radiographic images. The non-ionic nature of iopamidol results in lower osmolality (approximately 796 mOsm/kg water for 370 mgI/mL solution) compared to ionic contrast media, reducing the risk of adverse reactions related to hyperosmolarity.
Indications
- Cerebral angiography and ventriculography
- Coronary arteriography and left ventriculography
- Peripheral arteriography and venography
- Excretory urography
- Contrast-enhanced computed tomography (CT) of head, body, and extremities
- Arthrography
- Myelography (lumbar only)
- Gastrointestinal tract imaging
Dosage and Administration
Administration: Intravenous, intra-arterial, intrathecal (lumbar route only), or oral/rectal routes depending on procedure Standard Dosing:- CT of head: 50-150 mL (300-370 mgI/mL)
- Body CT: 75-150 mL (300-370 mgI/mL)
- Coronary arteriography: 4-8 mL injections (370 mgI/mL)
- Excretory urography: 50 mL (300-370 mgI/mL)
- Peripheral arteriography: 20-60 mL (300-370 mgI/mL)
- Renal impairment: Use caution; ensure adequate hydration
- Hepatic impairment: No specific dosage adjustment required
- Elderly: Reduced dose may be necessary due to decreased renal function
- Pediatrics: Dose based on body weight (1-3 mL/kg)
Pharmacokinetics
Absorption: Complete when administered parenterally; minimal absorption from GI tract Distribution: Distributed rapidly in extracellular fluid; does not cross intact blood-brain barrier; volume of distribution approximately 0.26 L/kg Metabolism: Not metabolized; remains unchanged in circulation Elimination: Excreted unchanged by glomerular filtration; elimination half-life 2-4 hours in normal renal function; prolonged in renal impairment Protein Binding: <10%Contraindications
- History of severe hypersensitivity reactions to iodinated contrast media
- Patients with manifest hyperthyroidism
- Intrathecal administration in patients with known sensitivity to intrathecal contrast media
- Use during pregnancy unless clearly needed (Category B)
Warnings and Precautions
Contrast-Induced Nephropathy: Risk increased in patients with pre-existing renal impairment, diabetes, dehydration, or concomitant nephrotoxic drugs Anaphylactoid Reactions: May occur without warning; have emergency equipment available Extravasation: Can cause tissue irritation, compartment syndrome, or necrosis Thyroid Function: May interfere with thyroid function tests for weeks following administration Sickle Cell Disease: Use with caution due to risk of sickling crisis Myasthenia Gravis: May exacerbate symptoms Pheochromocytoma: May precipitate hypertensive crisisDrug Interactions
- Nephrotoxic drugs (aminoglycosides, NSAIDs, vancomycin): Increased risk of contrast-induced nephropathy
- Metformin: Temporary discontinuation recommended in patients with renal impairment
- Interferon: Associated with increased risk of nephrotoxicity
- Interleukin-2: May increase risk of adverse reactions
Adverse Effects
Common (≥1%):- Warm sensation/flushing
- Nausea
- Headache
- Taste perversion
- Pain at injection site
- Anaphylactoid reactions (bronchospasm, angioedema, hypotension)
- Contrast-induced nephropathy
- Cardiac arrhythmias
- Seizures (particularly with intrathecal administration)
- Thyrotoxicosis
- Extravasation injury
Monitoring Parameters
- Renal function (serum creatinine) before and 48-72 hours after administration in high-risk patients
- Vital signs during and immediately after administration
- Signs of hypersensitivity reactions
- Neurological status after intrathecal administration
- Thyroid function in susceptible patients
- Injection site for extravasation
Patient Education
- Inform your physician about any allergies, especially to contrast media or shellfish
- Report any history of kidney disease, diabetes, or thyroid problems
- Maintain adequate hydration before and after the procedure
- Immediately report any symptoms of allergic reaction (hives, itching, difficulty breathing)
- Be aware that you may experience a warm sensation or metallic taste during injection
- Inform radiology staff if you are pregnant or breastfeeding
- After the procedure, increase fluid intake unless contraindicated
References
1. American College of Radiology. ACR Manual on Contrast Media. 2023. 2. FDA Prescribing Information: Isovue (Iopamidol Injection). 3. Thomsen HS, Morcos SK. Contrast media and the kidney: European Society of Urogenital Radiology (ESUR) guidelines. Br J Radiol. 2003;76(908):513-518. 4. Davenport MS, Perazella MA, Yee J, et al. Use of intravenous contrast media in patients with kidney disease: consensus statements from the American College of Radiology and the National Kidney Foundation. Radiology. 2020;294(3):660-668. 5. Katzberg RW, Haller C. Contrast-induced nephrotoxicity: clinical landscape. Kidney Int Suppl. 2006;(100):S3-S7. 6. European Society of Urogenital Radiology. ESUR Contrast Media Safety Guidelines. 2022.