Iohexol

Pronunciation: eye-oh-HEX-ol.

Generic name
iohexol
Drug class
Non-ionic iodinated (tri-iodinated) radiographic contrast medium
Form
Injection/solution (multiple iodine concentrations: 140, 180, 240, 300, 350 mg iodine/mL) and oral solution
Route
Intrathecal, intra-arterial, intravenous, oral, rectal, intra-articular, or body-cavity use, depending on the imaging procedure
Legal status
Prescription-only, administered by or under the supervision of a clinician/radiology team

Availability and supply rules vary by country

Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand

Australia: Omnipaque (5) · Full directory

What iohexol is and how it works

Iohexol is a contrast medium (sometimes called a 'contrast dye') used to make certain body structures show up more clearly on X-ray-based imaging, including CT scans, angiography, myelography, and various other procedures. It does not treat any disease itself -- it is a diagnostic aid given immediately before or during an imaging procedure by a clinician or radiology team. (1) (2)

Iohexol carries a genuine, serious boxed-warning risk specific to spinal (intrathecal) procedures: giving the wrong strength into the spinal fluid, even by accident, can cause death or severe permanent injury -- this is why it is always selected and given by trained staff, never something you administer yourself. Separately, like other iodinated contrast agents, it carries real risks of kidney injury (especially if you have kidney problems, diabetes, or are dehydrated), serious allergic reactions, and, in infants under 3, a risk of temporary thyroid problems.

Mechanism of action: how iohexol works

Iohexol is a non-ionic, monomeric, tri-iodinated, water-soluble radiographic contrast medium. It increases X-ray attenuation (radiodensity) of the body fluid or cavity it is introduced into, allowing greater visual contrast on X-ray-based imaging. Following intravascular injection, iohexol is not metabolised and is excreted essentially unchanged by the kidneys (close to 100% within 24 hours in patients with normal renal function); pharmacokinetic parameters include a distribution half-life of approximately 22 minutes, an excretion half-life of approximately 2.1 hours, and a terminal elimination half-life of approximately 12.6 hours, with mean renal clearance around 120 mL/min. (2) (4)

What iohexol is used for

Imaging of the brain and spine (myelography, CT myelography/cisternography)

Given into the spinal fluid (intrathecally) to help visualise the spinal cord, nerve roots, and surrounding structures on X-ray or CT imaging. (1) (2)

Blood vessel and heart imaging (angiography, cardiac catheterisation)

Given into an artery or vein to help visualise blood vessels and heart structures, including coronary arteriography, aortography, and cerebral/peripheral arteriography. (1) (2)

CT scanning and urography

Given intravenously to enhance CT images of the head and body, and to visualise the kidneys and urinary tract (excretory urography). (1) (2)

Gastrointestinal tract imaging

Taken by mouth or given rectally to help visualise the digestive tract on X-ray or CT imaging. (1) (4)

Joint imaging (arthrography)

Injected directly into a joint (such as the knee or shoulder) to help visualise joint structures on imaging. (1) (4)

Before taking iohexol

Do not take / not appropriate for

  • Iohexol must not be given intrathecally (into the spinal fluid) at the wrong iodine concentration -- only the specific concentrations and presentations approved for intrathecal use may ever be used this way. (all countries) (1)
  • Iohexol must not be used if you have a known hypersensitivity to iohexol or its excipients. (United Kingdom, and consistent with US labeling reviewed) (2)
  • Iohexol must not be used if you have manifest (overt, untreated) thyrotoxicosis. (United Kingdom) (2)
  • Iohexol for hysterosalpingography must not be used during pregnancy or suspected pregnancy, during or near menstruation, within 6 months after a pregnancy ends, within 30 days after conization/curettage, or when there are signs of genital-tract infection. (United States) (1)

Tell your clinician about

  • Any history of a reaction to contrast dye, asthma, or other drug/food allergies -- these increase the risk of a serious reaction to iohexol.
  • Your kidney function, especially if you have kidney disease, diabetes, heart failure, or are older, since these raise the risk of contrast-induced kidney injury.
  • Whether you take metformin, since combining it with contrast media and reduced kidney function can raise the risk of a serious condition called lactic acidosis.
  • Whether your child is under 3 years old (including if born prematurely or with a congenital heart condition), since infants in this age group have a specific risk of thyroid problems after contrast exposure.
  • Whether you are pregnant or could be pregnant, particularly before a hysterosalpingography procedure.
  • Any thyroid condition, including overactive thyroid (thyrotoxicosis).
(1) (2)

How to take iohexol

  • Iohexol is always selected, prepared, and administered by a clinician or radiology/imaging team -- you do not administer this medicine yourself.
  • The exact concentration, route (intrathecal, intravenous, oral, etc.), and dose depend entirely on which imaging procedure you are having -- these are not interchangeable.
  • You may be asked to drink extra fluids before and after the procedure to help protect your kidneys and help your body clear the contrast medium.
  • If you take metformin and are having a procedure involving intravascular contrast, your care team will advise you on whether and when to pause it, based on your kidney function.
(1) (6)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)

Missed dose

Not applicable -- iohexol is given once, during a specific imaging procedure, by a clinician or radiology team. There is no ongoing dosing schedule to miss.

Overdose

Overdose is a clinical emergency managed entirely by the treating team, since iohexol is administered under direct clinical supervision. Overdose effects from intra-arterial or intravenous administration are life-threatening and mainly affect the lungs and heart, including bluish skin discoloration, slow heart rate, acid-base imbalance, bleeding in the lungs, seizures, coma, and cardiac arrest. (1)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Feeling hot or a warm flushing sensation during or after the injection.

What to notice: Feeling hot or a warm flushing sensation during or after the injection.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (2)

Headache, nausea, and mild dizziness.

What to notice: Headache, nausea, and mild dizziness.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1) (2)

After intrathecal (spinal) use: headache, back or neck pain, nausea, vomiting, or dizziness.

What to notice: After intrathecal (spinal) use: headache, back or neck pain, nausea, vomiting, or dizziness.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

After oral use: diarrhoea, nausea, vomiting, or abdominal pain.

What to notice: After oral use: diarrhoea, nausea, vomiting, or abdominal pain.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

After joint (intra-articular) injection: pain, swelling, or a warm sensation at the injection site.

What to notice: After joint (intra-articular) injection: pain, swelling, or a warm sensation at the injection site.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Serious warnings

Signs of a wrong-concentration spinal (intrathecal) administration — boxed_warning

Symptoms: Severe headache, seizures, sudden severe back or neck pain, confusion, loss of consciousness, paralysis, or muscle rigidity following a spinal procedure.

Action: This is a medical emergency requiring immediate treatment by the clinical team present. This risk is why iohexol is always selected, prepared, and given by trained radiology/imaging staff. (1)

Signs of a serious allergic (anaphylactoid) reaction — boxed_warning_adjacent_serious

Symptoms: Difficulty breathing, wheezing, swelling of the face/lips/throat, widespread hives, or sudden low blood pressure -- most severe reactions occur within 1-3 minutes of the injection.

Action: This is why you will be monitored closely immediately after the injection, with emergency equipment and trained staff on hand. Tell your care team immediately about any new symptoms during or after the procedure. (1) (2)

Signs of kidney problems after the procedure — high caution

Symptoms: Decreased urination, swelling in the legs/ankles, unusual tiredness, or confusion in the days after the procedure.

Action: Contact your clinician promptly -- contrast-induced kidney injury is a known risk, especially with pre-existing kidney disease, diabetes, dehydration, or other kidney-affecting medicines. (1) (2)

Thyroid problems in infants after contrast exposure — high caution

Symptoms: In infants under 3 (especially premature or very young newborns), signs may not be obvious to parents and are typically found only through blood testing.

Action: Your child's care team will decide whether and when to check thyroid function after the procedure, based on your child's individual risk factors. (1) (6)

Interactions

  • Metformin: in people with diabetes who take metformin and have reduced kidney function, receiving iodinated contrast media raises the risk of a serious condition called lactic acidosis -- your care team will assess your kidney function and may advise pausing metformin around the procedure. (2)
  • Other nephrotoxic (kidney-affecting) medicines, when combined with iohexol, can increase the risk of contrast-induced kidney injury. (1)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

Use during pregnancy is decided by the treating clinician based on the specific imaging need; hysterosalpingography with iohexol is specifically contraindicated during pregnancy or suspected pregnancy. (1) (2) (3) (4) (5) (6)

Breastfeeding

Discuss timing of breastfeeding around a contrast procedure with your clinician. (1) (2) (3) (4) (5) (6)

Children

Used in children (including from 2 weeks of age for certain intrathecal procedures), with specific attention to thyroid function monitoring in those aged 0-3 years, especially premature or very young neonates. (1) (2) (3) (4) (5) (6)

Elderly

Older age is a recognised risk factor for contrast-induced kidney injury; kidney function is typically assessed before the procedure. (1) (2) (3) (4) (5) (6)

Hepatic_impairment

No specific dose adjustment identified in the sources reviewed; iohexol is primarily renally eliminated. (1) (2) (3) (4) (5) (6)

Renal_impairment

Pre-existing kidney impairment is a major risk factor for contrast-induced nephropathy/acute kidney injury; adequate hydration, the lowest necessary dose, and avoiding other nephrotoxic medicines around the time of the procedure are standard precautions. (1) (2) (3) (4) (5) (6)

Source_ids

US-DAILYMED-OMNIPAQUE-2026,UK-EMC-OMNIPAQUE-SMPC-2026,NZ-MEDSAFE-OMNIPAQUE-2026 (1) (2) (3) (4) (5) (6)

Monitoring

Before starting

  • Kidney function assessment, especially in those with diabetes, existing kidney disease, or other risk factors
  • Screening for prior contrast reactions, asthma, or significant drug/food allergies
  • Hydration status
  • Thyroid history, especially in infants under 3 and in those with known thyroid disease

During treatment

  • Close monitoring for signs of an allergic reaction immediately after administration (most severe reactions occur within 1-3 minutes).
  • Availability of emergency equipment and trained personnel during and immediately after the procedure.
(1) (2)

Storage

Stored and handled by the healthcare facility according to the product's specific storage instructions; not a medicine kept or stored by patients at home.

Professional information

Clinician-facing context only, sourced from the current US FDA and UK EMC labels reviewed for this dossier; verify against the current full label before use.

United States

Indication: Intrathecal myelography/CT myelography/cisternography

Dose summary: Only the specific low-iodine-concentration formulations and presentations labelled for intrathecal use may be used for this route, in patients aged 2 weeks and older.

Renal context: Not applicable to this route specifically; systemic renal precautions apply to intravascular routes. (1)

Canada

Indication: Arthrography and oral GI-tract imaging

Dose summary: Omnipaque 240 or 300 for knee arthrography; Omnipaque 300 for shoulder arthrography; Omnipaque 300 or 350 for oral GI-tract imaging.

Renal context: Standard contrast-induced nephropathy precautions apply for intravascular use; oral/intra-articular routes carry lower systemic absorption. (4)

Mechanism of action

Hepatic guidance

Not a primary route of elimination; iohexol is predominantly renally cleared.

Overdose note

Management of overdose or accidental wrong-route/wrong-concentration administration is supportive and symptomatic, focused on airway, breathing, circulation, and seizure control, in an appropriately equipped clinical setting. (2) (4)

Frequently asked questions

Why does iohexol have a boxed warning if it's just used for imaging, not to treat a disease?

Because a specific, catastrophic risk was identified: giving the wrong iodine-concentration formulation into the spinal fluid (intrathecally), even by accident, can cause death or severe permanent neurological injury. This is why only specific formulations are labelled and stocked for intrathecal use, and why iohexol is always prepared and given by trained radiology or imaging staff -- never something you would give yourself. (1)

Will I need to do anything to prepare for a procedure using iohexol?

Your care team will give you specific instructions, which may include drinking extra fluids before and after the procedure, telling them about your kidney function and any allergies, and discussing whether to pause metformin if you take it. Always follow your own care team's specific instructions rather than general guidance. (2)

Is iohexol safe for children?

Iohexol is used in children, including from 2 weeks of age for certain procedures, but infants under 3 years old (especially those born prematurely or with certain heart conditions) have a specific, recognised risk of temporary thyroid dysfunction after exposure. Your child's care team will individualise monitoring based on your child's specific risk factors. (1) (6)

What is the mechanism of action of iohexol?

Iohexol is a non-ionic, monomeric, tri-iodinated, water-soluble radiographic contrast medium. It increases X-ray attenuation (radiodensity) of the body fluid or cavity it is introduced into, allowing greater visual contrast on X-ray-based imaging. Following intravascular injection, iohexol is not metabolised and is excreted essentially unchanged by the kidneys (close to 100% within 24 hours in patients with normal renal function); pharmacokinetic parameters include a distribution half-life of approximately 22 minutes, an excretion half-life of approximately 2.1 hours, and a terminal elimination half-life of approximately 12.6 hours, with mean renal clearance around 120 mL/min. (2) (4)

What is the generic name of Iohexol?

The generic name is iohexol. (1) (3)

What class of drug is iohexol?

Iohexol is classed as: Non-ionic iodinated (tri-iodinated) radiographic contrast medium. (1) (3)

References

  1. OMNIPAQUE (iohexol) injection, solution / oral solution -- full prescribing informationU.S. Food and Drug Administration / DailyMed (NIH), full prescribing information, GE Healthcare · United States · accessed 2026-07-31 · source 1
  2. Omnipaque Injection 300mg I/ml solution for injection -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom -- GE Healthcare Limited · United Kingdom · accessed 2026-07-31 · source 2
  3. Iohexol -- list of nationally authorised medicinal products (PSUSA/00001768/202006)European Medicines Agency (EMA) -- PSUSA nationally-authorised-medicinal-products list for iohexol · European Union · accessed 2026-07-31 · source 3
  4. OMNIPAQUE (iohexol injection USP) -- Product MonographHealth Canada product monograph, GE Healthcare Canada Inc. · Canada · accessed 2026-07-31 · source 4
  5. OMNIPAQUE iohexol injection -- multiple ARTG entries (e.g. 15474, 76060, 76065, 76066, 76072, 39868, 48220, 48238, 348754, 348758)Therapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-31 · source 5
  6. OMNIPAQUE (iohexol) injection -- New Zealand Data SheetMedsafe (New Zealand Medicines and Medical Devices Safety Authority) · New Zealand · accessed 2026-07-31 · source 6

Brand names by country

Single-ingredient iohexol names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • Omnipaque180 mg/mL, 140 mg/mL, 9 mg/mL, 350 mg/mL, 12 mg/mL, 300 mg/mL, 240 mg/mL · ge healthcare inc.

United Kingdom

  • Omnipaque (2)MHRA licensed emc smpc confirmed · 140 mg I/mL, 240 mg I/mL, 300 mg I/mL, 350 mg I/mL · GE Healthcare Limited

Canada

  • OMNIPAQUE

Australia

  • Omnipaque (5)TGA ARTG registered confirmed multiple entries since 1991 · 140 mg I/mL, 240 mg I/mL, 300 mg I/mL, 350 mg I/mL · GE Healthcare Australia Pty Ltd

New Zealand

  • Omnipaque (6)Medsafe data sheet confirmed current · 240 mg I/mL, 300 mg I/mL, 350 mg I/mL · GE Healthcare (New Zealand)
View brands in additional countries.

European Union

Omnipaque (and other iohexol-containing brands) (3)

This page provides general reference information about iohexol (Omnipaque) and is not a substitute for advice from the clinician or radiology team performing your procedure. This medicine is always selected, prepared, and administered by trained healthcare staff -- it is never self-administered.

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