Omnipaque (Iohexol): Uses, Dosage & Side Effects
Non-ionic iodinated contrast agent for diagnostic imaging
Omnipaque (iohexol) is a non-ionic, low-osmolar, iodinated contrast agent widely used in diagnostic radiology. It enhances the visibility of internal structures during X-ray and CT scan imaging, helping physicians distinguish between normal and abnormal tissues. Omnipaque is administered via injection into veins, arteries, or the spinal canal, and can also be taken orally for gastrointestinal studies. It is one of the most commonly used contrast media worldwide with an established safety profile spanning over three decades of clinical use.
Quick Facts
Key Takeaways
- Omnipaque is a non-ionic, low-osmolar iodinated contrast agent used to improve diagnostic imaging quality in CT scans, angiography, myelography, urography, and gastrointestinal studies.
- It contains iodine and is contraindicated in patients with severe thyroid disease or known allergy to iohexol. Patients must inform their doctor about any previous contrast reactions.
- Adequate hydration before and after the procedure is essential, especially in patients with kidney disease, diabetes, or multiple myeloma, to reduce the risk of contrast-induced nephropathy.
- Common side effects include warmth sensation, nausea, and sweating; severe allergic reactions (anaphylaxis) are rare but require immediate medical attention.
- Metformin should be temporarily discontinued in patients receiving intravascular Omnipaque to reduce the risk of lactic acidosis, following current ACR guidelines.
What Is Omnipaque and What Is It Used For?
Omnipaque belongs to a class of medications known as non-ionic iodinated contrast media. These agents work by absorbing X-rays more effectively than the surrounding soft tissues, creating a contrast that allows radiologists to visualize blood vessels, organs, and other internal structures with greater clarity. As a non-ionic formulation, Omnipaque has a lower osmolality than older ionic contrast agents, which significantly reduces the incidence of adverse reactions.
Iohexol, the active ingredient in Omnipaque, was first developed by Nycomed (now part of GE Healthcare) and received regulatory approval in the early 1980s. Since its introduction, it has become one of the most widely used contrast agents globally, with billions of doses administered worldwide. Its favorable safety profile and versatility across different imaging applications have made it a cornerstone of modern diagnostic radiology.
Omnipaque is used across a wide range of diagnostic procedures. When injected intravenously, it is most commonly used to enhance computed tomography (CT) scans of the head, chest, abdomen, and pelvis. Intra-arterial administration is used for angiography, including coronary, cerebral, and peripheral vascular studies. Intrathecal injection allows visualization of the spinal canal in myelographic examinations. The agent can also be administered directly into body cavities for arthrography (joint imaging), hysterosalpingography (uterine and fallopian tube imaging), and sialography (salivary gland imaging).
In addition to injectable uses, Omnipaque can be given orally or rectally for gastrointestinal imaging. When used orally, it opacifies the esophagus, stomach, and small intestine, while rectal administration allows visualization of the colon. This is particularly useful in contrast-enhanced mammography, where it enables detection of areas with increased blood supply that may indicate breast lesions.
Omnipaque is distributed exclusively in the extracellular fluid compartment after intravascular injection. It does not cross the intact blood-brain barrier and is not metabolized by the body. Approximately 90% of the injected dose is eliminated by glomerular filtration within 24 hours in patients with normal kidney function, with the elimination half-life being approximately 2 hours.
What Should You Know Before Receiving Omnipaque?
Contraindications
Omnipaque must not be used in patients with a known hypersensitivity to iohexol or any of its excipients. In addition, it is contraindicated in patients with manifest thyrotoxicosis (severe overactive thyroid), as the iodine content can exacerbate this condition. These absolute contraindications are established by the European Medicines Agency (EMA) and the United States Food and Drug Administration (FDA) and must be strictly observed by healthcare professionals.
- You have severe thyroid problems (thyrotoxicosis)
- You are allergic to iohexol or any ingredient in Omnipaque
Warnings and Precautions
Several medical conditions require careful evaluation before Omnipaque can be administered. The American College of Radiology (ACR) Manual on Contrast Media provides comprehensive guidance on risk stratification and management. Healthcare providers should be informed about the following conditions:
- Previous contrast reactions: Patients who have experienced an allergic or adverse reaction to any contrast agent are at increased risk of a repeat reaction. Premedication with corticosteroids and antihistamines should be considered according to ACR guidelines.
- Kidney disease: Pre-existing renal impairment increases the risk of contrast-induced nephropathy (CIN). Kidney function should be assessed before administration, and alternative non-contrast imaging should be considered when possible. Adequate hydration with intravenous normal saline is the most important preventive measure.
- Thyroid disorders: The iodine in Omnipaque may affect thyroid function. Patients with known thyroid problems, including those with multinodular goiter, should be carefully evaluated. Thyroid function tests may be affected for several weeks after administration.
- Diabetes mellitus: Diabetic patients, particularly those with renal impairment, are at higher risk for contrast-induced nephropathy. Metformin use requires special management protocols (see Drug Interactions section).
- Heart disease: Patients with severe cardiovascular disease, including heart failure, unstable angina, or recent myocardial infarction, face an increased risk of cardiac complications during contrast-enhanced procedures, particularly coronary angiography.
- Epilepsy or neurological conditions: Patients with a history of seizures or other cerebral disorders may be at increased risk of neurological complications, especially with intrathecal administration.
- Pheochromocytoma: Patients with catecholamine-secreting tumors may experience a hypertensive crisis. Alpha-adrenergic blockade should be considered before the procedure.
- Myasthenia gravis: Iodinated contrast agents may exacerbate symptoms of myasthenia gravis, a condition causing severe muscle weakness.
- Pulmonary hypertension: Patients with elevated pulmonary artery pressures may be at increased risk of hemodynamic complications.
- Paraproteinemia: Conditions such as multiple myeloma with significantly elevated blood protein levels increase the risk of renal toxicity.
- Alcohol or drug dependence: Active substance use disorders may increase the risk of seizures.
- Autoimmune diseases: Certain autoimmune conditions may increase the risk of adverse reactions.
Ensure adequate fluid intake before and after the imaging procedure. This is particularly important for elderly patients, children, patients with diabetes, kidney disease, multiple myeloma, or those in poor general health. Hydration helps the kidneys eliminate the contrast agent more efficiently and reduces the risk of contrast-induced nephropathy.
Children and Adolescents
Omnipaque can be used in pediatric patients, but special care is required. Infants under 1 year, particularly neonates, are especially susceptible to electrolyte imbalances and changes in hemodynamics. Adequate hydration before and after the procedure is critical, and nephrotoxic medications should be avoided. Thyroid dysfunction, including transient hypothyroidism, has been reported in children and adolescents after receiving iodinated contrast agents, with premature infants being particularly vulnerable due to their immature thyroid function.
Pregnancy and Breastfeeding
Omnipaque should only be used during pregnancy if the physician determines that the benefit outweighs the potential risk to both the mother and the fetus. Iodinated contrast agents can cross the placenta and may affect fetal thyroid function. If Omnipaque is administered during pregnancy, thyroid function in the newborn should be monitored during the first week of life, as recommended by the European Society of Urogenital Radiology (ESUR).
Breastfeeding can continue as normal after receiving Omnipaque. Only minimal amounts of iohexol are excreted into breast milk (less than 1% of the administered dose), and the substance is poorly absorbed from the infant's gastrointestinal tract. Both the ACR and ESUR confirm that interruption of breastfeeding is not necessary after administration of iodinated contrast media.
Driving and Operating Machinery
Patients should not drive or operate machinery for at least one hour after the last injection of Omnipaque, or for 24 hours after intrathecal administration (injection into the spinal canal). Dizziness, visual disturbances, and other symptoms may impair the ability to perform these activities safely.
How Does Omnipaque Interact with Other Drugs?
Drug interactions with iodinated contrast agents like Omnipaque can range from mild to life-threatening. Healthcare professionals should conduct a thorough medication review before any contrast-enhanced procedure. The following table summarizes the most important drug interactions recognized by major regulatory agencies and clinical guidelines.
| Drug / Class | Interaction | Management |
|---|---|---|
| Metformin | Risk of lactic acidosis in patients with renal impairment when combined with intravascular iodinated contrast | Withhold metformin at time of or before procedure; restart 48 hours after if renal function is stable (ACR guidelines) |
| Beta-blockers (atenolol, metoprolol) | May reduce effectiveness of epinephrine treatment for anaphylaxis; may increase risk of bronchospasm | Increased vigilance; consider glucagon for refractory hypotension in anaphylaxis |
| Interleukin-2 / Interferons | Increased risk of delayed contrast reactions, including hypotension, fever, and flu-like symptoms | Extended observation period recommended; premedication may be considered |
| Nephrotoxic drugs (aminoglycosides, NSAIDs, vancomycin) | Additive nephrotoxic effect, increased risk of contrast-induced nephropathy | Avoid concurrent use if possible; ensure adequate hydration; monitor renal function |
| ACE inhibitors / ARBs (ramipril, losartan) | May increase risk of contrast-induced nephropathy due to altered renal hemodynamics | Withholding is controversial; ensure adequate hydration and monitor renal function |
| Tricyclic antidepressants / Neuroleptics | May lower seizure threshold, particularly relevant for intrathecal administration | Inform radiologist; consider alternative imaging if seizure risk is high |
Laboratory Test Interference
Omnipaque can interfere with several laboratory tests. Thyroid function tests may be affected for several weeks after administration due to the iodine content. Blood and urine samples collected on the same day as contrast administration may show altered results for certain parameters. Patients should inform their healthcare provider about recent contrast exposure when having blood or urine tests performed.
What Is the Correct Dosage of Omnipaque?
Unlike most medications, Omnipaque does not have a fixed dosing schedule that patients follow at home. It is exclusively administered by trained medical personnel in a hospital or imaging center. The dose, concentration, and route of administration are determined by the radiologist based on the specific diagnostic procedure being performed. Multiple concentrations are available (140, 180, 240, 300, and 350 mg I/mL) to accommodate different clinical needs.
Routes of Administration
Intravenous / Intra-arterial Injection
The most common route. Omnipaque is injected into a vein (usually in the arm) or through a catheter placed in an artery (typically in the arm or groin). For CT scans, concentrations of 300 or 350 mg I/mL are typically used, with volumes ranging from 50 to 200 mL depending on the body region and patient size. For coronary angiography, total volumes of 150-250 mL at 350 mg I/mL are common.
Intrathecal Injection (Myelography)
For spinal imaging, lower concentrations (180 or 240 mg I/mL) are used with typical volumes of 10-17 mL for lumbar myelography. The patient must remain with head and torso elevated for at least one hour after injection, or six hours if resting in bed, to prevent the contrast from migrating to the brain.
Oral Administration
For gastrointestinal imaging, Omnipaque can be diluted with water and administered as a drink. Concentrations of 140 or 180 mg I/mL are typically used. The volume varies depending on the area being examined (esophagus, stomach, or small intestine).
Body Cavity Administration
For arthrography (joint imaging), hysterosalpingography (uterine imaging), and other cavity studies, specific concentrations and volumes are determined based on the anatomical site. Concentrations of 240 or 300 mg I/mL are commonly used.
Special Populations
| Patient Group | Considerations |
|---|---|
| Adults | Standard dosing based on procedure type and body weight. Maximum total iodine dose generally should not exceed 80 g iodine per procedure. |
| Children | Dose calculated based on body weight (typically 1-3 mL/kg for IV CT). Adequate hydration is critical. Neonates and infants require careful monitoring. |
| Elderly | Lower doses may be appropriate. Increased risk of dehydration and renal impairment. Ensure adequate hydration before and after the procedure. |
| Renal impairment | Use lowest effective dose. Ensure aggressive hydration. Consider alternative imaging modalities. Monitor kidney function after the procedure. |
After Receiving Omnipaque
After receiving Omnipaque, patients should drink plenty of fluids to help the kidneys eliminate the contrast agent. All patients are typically monitored for at least 30 minutes in the imaging department and should remain at the hospital or clinic for at least one hour. This observation period is essential because most serious adverse reactions, including anaphylaxis, occur within the first 30 minutes after administration. Delayed reactions can occur hours to days later, and patients should be instructed to seek immediate medical attention if they experience any unusual symptoms after leaving the facility.
Special Precautions After Intrathecal Use
Patients who receive Omnipaque via intrathecal injection for myelography must follow specific post-procedural instructions to minimize neurological complications:
- Keep the head and upper body elevated for at least one hour, or six hours if resting in bed
- Walk carefully and avoid bending forward for six hours
- Outpatients with a history of seizures should not be left alone for the first 24 hours
- Do not drive or operate machinery for 24 hours
What Are the Side Effects of Omnipaque?
Like all contrast media, Omnipaque can cause side effects, although not everyone will experience them. The safety profile of non-ionic contrast agents like iohexol is significantly better than that of older ionic agents, with overall adverse reaction rates typically below 5%. However, healthcare professionals and patients should be aware of the full spectrum of possible reactions, ranging from mild transient effects to rare life-threatening complications.
- Difficulty breathing, wheezing, or chest tightness
- Swelling of the face, throat, or tongue
- Severe skin rash, blisters, or hives
- Dizziness, fainting, or rapid heartbeat
- Confusion, seizures, or loss of consciousness
General Side Effects (All Routes of Administration)
Common (up to 1 in 10 patients)
May affect up to 10% of patients
- Sensation of warmth or heat throughout the body
Uncommon (up to 1 in 100 patients)
May affect up to 1% of patients
- Nausea
- Increased or abnormal sweating
- Cold sensation
- Dizziness or light-headedness
- Headache
Rare (up to 1 in 1,000 patients)
May affect up to 0.1% of patients
- Allergic reactions (skin rash, itching, breathing difficulties) — potentially life-threatening
- Slow heart rate (bradycardia)
- Abdominal pain
- Vomiting
- Fever
Very Rare (up to 1 in 10,000 patients)
May affect up to 0.01% of patients
- Temporary taste disturbance (dysgeusia)
- Fainting due to sudden blood pressure drop
- High or low blood pressure
- Chills
- Diarrhea
- Severe allergic reaction (anaphylactic shock)
Frequency Not Known
Reported from post-marketing surveillance
- Swollen and painful salivary glands (iodism)
Side Effects After Intravenous or Intra-arterial Injection
The following additional side effects have been reported specifically after intravascular administration of Omnipaque. These effects are related to the vascular distribution of the contrast agent and its osmotic properties.
Common
- Short-term changes in breathing rate
Uncommon
- Pain and discomfort at injection site
- Acute kidney injury
Rare
- Irregular heartbeat (arrhythmias)
- Cough, respiratory arrest
- Dizziness, weakness, muscle weakness
- Photosensitivity
- Skin rash, itching, skin redness
- Visual disturbances (blurred or double vision)
- Fatigue
- Diarrhea
Very Rare
- Seizures, altered consciousness, stroke
- Sensory disturbances, tremor, stupor
- Flushing
- Respiratory difficulties
- Myocardial infarction (heart attack)
- Chest pain
Frequency Not Known
- Contrast encephalopathy (temporary brain dysfunction causing headache, visual disturbances, confusion, seizures, or loss of consciousness)
- Thyroid dysfunction (hyperthyroidism or transient hypothyroidism)
- Transient blindness (hours to days), transient hearing loss
- Heart failure, coronary artery spasm, cyanosis
- Pulmonary edema, bronchospasm
- Worsening of pancreatitis
- Venous thrombosis, phlebitis
- Joint pain, muscle spasms, back pain
- Psoriasis flare
- Asthma attack
- Thrombocytopenia (low platelet count)
- Elevated blood creatinine
Side Effects After Intrathecal Injection (Myelography)
Very Common (more than 1 in 10 patients)
May affect more than 10% of patients
- Headache (may be severe and persistent)
Common
- Nausea and vomiting
- Nerve pain
Uncommon
- Meningitis (inflammation of the membranes surrounding the brain and spinal cord)
Rare
- Seizures
- Dizziness
- Pain in arms, legs, neck, or back
Frequency Not Known
- Confusion, agitation, anxiety, disorientation
- Photosensitivity, neck stiffness
- Transient motor dysfunction, sensory disturbances
- Transient blindness, transient hearing loss
- Contrast encephalopathy
- Speech disorders including aphasia (inability to speak) and dysarthria (difficulty articulating words)
Side Effects After Oral Administration
Very Common
- Diarrhea
Common
- Nausea and vomiting
Uncommon
- Abdominal pain
Side Effects After Use in Body Cavities
When Omnipaque is used in body cavities (such as the uterus, bladder, or blood vessels), the most common side effect is abdominal pain, reported in more than 1 in 10 patients. Inflammation of the pancreas (pancreatitis) and elevated blood amylase levels have been reported as common side effects. When injected into joints, pain is very common, and joint inflammation has been reported.
Side Effects in Children
Transient hypothyroidism (temporary underactive thyroid) has been reported in premature infants, neonates, and other children after receiving Omnipaque. Premature infants are particularly susceptible to the effects of iodine on thyroid function. Transient hypothyroidism has also been observed in premature infants who were breastfed by mothers who received repeated contrast examinations with Omnipaque. In most cases, no symptoms are observed and thyroid function returns to normal without intervention.
How Should Omnipaque Be Stored?
As Omnipaque is administered exclusively in healthcare facilities, patients do not need to worry about storage. However, the following storage requirements apply to healthcare institutions:
- Storage temperature: Store at room temperature in the original outer carton to protect from light
- Do not freeze: Omnipaque must never be frozen, as this can affect the solution's properties
- Warming: The solution may be stored in a warming cabinet at 37°C (98.6°F) for up to one month before use. Warming the contrast to body temperature reduces discomfort during injection
- Visual inspection: Before use, the solution must be visually inspected. It should be clear, colorless to pale yellow, and free of visible particles. The container must be intact
- Expiry date: Do not use after the expiry date printed on the label
- Keep out of sight and reach of children
What Does Omnipaque Contain?
Omnipaque is a sterile, clear, colorless to pale yellow aqueous solution available in five different iodine concentrations. The active substance, iohexol, is a non-ionic, tri-iodinated benzene derivative with three iodine atoms per molecule. It is the iodine atoms that provide the X-ray attenuation necessary for diagnostic imaging.
| Formulation | Iodine Content | Common Uses |
|---|---|---|
| Omnipaque 140 | 140 mg I/mL | Oral GI studies, sialography |
| Omnipaque 180 | 180 mg I/mL | Myelography, oral GI studies |
| Omnipaque 240 | 240 mg I/mL | Myelography, arthrography, urography |
| Omnipaque 300 | 300 mg I/mL | CT scanning, urography, angiography |
| Omnipaque 350 | 350 mg I/mL | CT scanning, coronary angiography, peripheral angiography |
Excipients
- Trometamol (tromethamine): A buffer used to maintain the solution at physiological pH
- Sodium calcium edetate: A chelating agent that binds trace metal ions, improving the stability and safety of the solution
- Hydrochloric acid: Used for pH adjustment to ensure the solution is within the appropriate pH range
- Water for injections: The solvent used to create the sterile aqueous solution
Omnipaque contains less than 1 mmol of sodium (23 mg) per mL, meaning it is essentially sodium-free. This is an important consideration for patients on sodium-restricted diets or those with conditions requiring strict fluid and electrolyte management.
Packaging
Omnipaque is available in glass vials and polymer bottles (USB bottles) in various sizes ranging from 10 mL to 1000 mL, depending on the concentration. Not all pack sizes may be marketed in every country. The choice of container size depends on the specific imaging procedure and clinical requirements.
Frequently Asked Questions About Omnipaque
Omnipaque (iohexol) is a non-ionic iodinated contrast agent used to enhance visibility during diagnostic imaging procedures. It is commonly used in CT scans (computed tomography), angiography (blood vessel imaging), myelography (spinal canal imaging), urography (urinary tract imaging), arthrography (joint imaging), and gastrointestinal studies. It makes internal structures appear more clearly on X-ray and CT images, helping doctors identify abnormalities.
Patients with pre-existing kidney problems are at increased risk for contrast-induced nephropathy (CIN) when receiving Omnipaque. However, the risk can be significantly reduced through adequate hydration before and after the procedure, using the lowest effective dose, and avoiding concurrent nephrotoxic medications. Kidney function should be assessed before administration using serum creatinine or eGFR levels. Your doctor will weigh the diagnostic benefit against the renal risk for your specific situation.
Yes, allergic reactions to Omnipaque can occur, though they are less common with non-ionic contrast agents like iohexol compared to older ionic agents. Reactions range from mild (hives, itching, nausea) to severe (anaphylaxis with breathing difficulty, severe hypotension, and cardiac arrest). Patients with a history of previous contrast reactions, asthma, or multiple allergies are at higher risk. Pre-medication with corticosteroids and antihistamines may be given to high-risk patients. Reactions can occur immediately or be delayed by hours to days.
Yes, because Omnipaque contains iodine, it can affect thyroid function. Both overactive thyroid (hyperthyroidism) and temporary underactive thyroid (transient hypothyroidism) have been reported. Premature infants and neonates are particularly vulnerable. Thyroid function tests may also be unreliable for several weeks after contrast administration. Patients with known thyroid disorders or those scheduled for thyroid tests should discuss this with their doctor before the procedure.
Yes, breastfeeding can continue as normal after receiving Omnipaque. Less than 1% of the administered dose is excreted into breast milk, and iohexol is very poorly absorbed from the infant's gastrointestinal tract. This position is supported by the American College of Radiology (ACR), the European Society of Urogenital Radiology (ESUR), and other major medical organizations. There is no need to pump and discard breast milk after receiving iodinated contrast agents.
In patients with normal kidney function, approximately 90% of Omnipaque is eliminated through the kidneys within 24 hours of administration. The elimination half-life is approximately 2 hours. In patients with impaired renal function, elimination takes longer and may require several days. Drinking plenty of fluids after the procedure helps the kidneys clear the contrast agent more quickly. Omnipaque is not metabolized by the body and is excreted unchanged in the urine.
References
- European Medicines Agency (EMA). Omnipaque Summary of Product Characteristics (SmPC). Last updated 2024.
- U.S. Food and Drug Administration (FDA). Omnipaque Prescribing Information. GE Healthcare Inc. Reference ID: 4799424.
- American College of Radiology (ACR). ACR Manual on Contrast Media, Version 2024. ACR Committee on Drugs and Contrast Media.
- European Society of Urogenital Radiology (ESUR). ESUR Guidelines on Contrast Agents, Version 10.0, 2023.
- Stacul F, et al. Contrast induced nephropathy: updated ESUR Contrast Media Safety Committee guidelines. European Radiology. 2011;21(12):2527-2541.
- Katayama H, et al. Adverse reactions to ionic and nonionic contrast media: A report from the Japanese Committee on the Safety of Contrast Media. Radiology. 1990;175(3):621-628.
- World Health Organization (WHO). WHO Model List of Essential Medicines, 23rd List, 2023. Iohexol is included as a diagnostic agent.
- Morcos SK, Thomsen HS. Adverse reactions to iodinated contrast media. European Radiology. 2001;11(7):1267-1275.
- Davenport MS, et al. ACR Appropriateness Criteria: Contrast Media for Imaging. Journal of the American College of Radiology. 2023;20(11S):S573-S587.
- Lee SY, et al. Contrast-enhanced CT: Evidence-based practice. Korean Journal of Radiology. 2021;22(12):1925-1941.
Medical Editorial Team
This article has been medically reviewed by the iMedic Medical Review Board, a team of board-certified physicians with expertise in radiology, pharmacology, and diagnostic imaging. All medical claims are evidence-based and grounded in current international guidelines from the ACR, ESUR, EMA, and FDA.
All content follows the GRADE evidence framework. Drug information is sourced from regulatory-approved product labeling (EMA SmPC, FDA prescribing information) and peer-reviewed clinical literature.
iMedic receives no pharmaceutical industry funding. All content is produced independently by our medical editorial team without commercial influence or advertising sponsorship.