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Overview: Iohexol is a contrast agent that is used for certain imaging tests. It works by blocking X-ray beams, which helps blood vessels and structures show up more clearly on images. Common side effects may include headache, back or neck pain, stiffness, nausea and vomiting, and blurry vision. While less common, serious side effects may include heart problems, kidney damage, blood clots, or skin and injection site reactions. Iohexol comes in forms that may be swallowed, inserted into the rectum, or injected into a blood vessel, joint, body cavity, or into or near the spine.

Uses

What is iohexol used for?

Iohexol is commonly used for certain imaging tests, such as X-rays or CT scans.

Iohexol may also be used for other conditions as determined by your health care provider.

How does iohexol work (mechanism of action)?

Iohexol is an iodine-based contrast dye (also called a contrast material or contrast agent). It works by blocking X-ray beams. This helps blood vessels and body structures show up more clearly on imaging tests, which makes it easier to see both normal and abnormal tissue.

How is iohexol supplied (dosage forms)?

Brands and other names

  • Omnipaque

Dosage forms and strengths

Iohexol is available in various forms that are given by a health care provider.

How should I store iohexol?

Iohexol is usually given by a health care provider in a hospital or clinic. You will not store it at home.

Side Effects

What are the most common side effects of iohexol?

The most common side effects of iohexol are listed below. These side effects may vary depending on how and where iohexol is given to you. Tell your health care provider if you have any of these side effects that bother you.

  • Headache
  • Pain in your back or neck
  • Stiffness
  • Nausea and vomiting
  • Dizziness
  • Vision changes, such as blurry vision
  • Bad or unusual taste in your mouth
  • Heart effects (see below)
  • Warm sensation
  • Diarrhea, stomach pain, or gas

There may be other side effects of iohexol that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088 (800-332-1088). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of iohexol?

While less common, the most serious side effects of iohexol are described below, along with what to do if they happen. These side effects may vary depending on how and where iohexol is administered. 

Severe Allergic Reactions. Iohexol may cause allergic reactions, which can be serious. Get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Heart Effects. Iohexol may have certain effects on the heart, such as lowering your blood pressure or causing an abnormal heart rhythm (arrhythmia). Tell your health care provider away if you have chest pain, dizziness, or a fast or irregular heartbeat, or if you feel your heartbeat more than usual.

Kidney Damage. Iohexol can cause kidney damage. The risk may be higher if you are dehydrated. Tell your health care provider right away if you have any of the following symptoms of kidney damage.

  • Reduced need to pee
  • Swelling in your feet, ankles, or legs
  • Weakness or unusual tiredness
  • Difficulty catching your breath or chest pain/pressure
  • Confusion
  • Nausea
  • Seizures

Blood Clots. Iohexol may cause blood clots in your arteries or veins and could cause a stroke, heart attack, or venous thromboembolism. Get emergency help if you have any of the following signs of blood clots.

  • Chest pain or pressure
  • Fast or abnormal heartbeat
  • Trouble breathing
  • Pain in your back, jaw, throat, or arm
  • Sweating, upset stomach, vomiting, or dizziness
  • Sudden weakness on one side of your body
  • Sudden and severe headache
  • Slurred speech or trouble understanding speech
  • Pain, swelling, or tenderness in your arm or leg
  • Vision loss

Severe Skin Reactions. Iohexol can cause severe skin reactions, such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), that can lead to death if not treated. These can happen up to several weeks after receiving iohexol by injection. If you get a rash, tell your health care provider right away. Get emergency help if you have any of the following symptoms of SJS or TEN.

  • Painful red or purple skin that looks burned and peels off
  • Flat red rash or blisters on your skin, mouth, nose, and genitals
  • Red, painful, watery eyes
  • Flu-like symptoms including fever, chills, and muscle aches

Injection Site Reactions. Injection site reactions can happen when iohexol is injected into a blood vessel. Symptoms may include pain, itching, swelling, or redness near the injection site. In rare cases, fluid can leak out of the blood vessel and could damage nearby tissues. Tell your health care provider right away if you have pain, swelling, warmth, or skin color changes where the medicine is being or was given.

Seizures. Seizures can happen when iohexol is injected into or near the spine. There are many different types of seizures and some of them are not easy to recognize. Tell your health care provider if you have any of the following signs that a seizure is happening or could happen.

  • Muscle twitching, jerking, spasms, tremors, or other uncontrolled movements
  • Stiffening of your arms and legs
  • Feeling anxious, nervous, confused, or a sense of dread
  • Feeling dizzy or lightheaded
  • Falling or losing consciousness

Warnings & Precautions

Who should not use iohexol?

Allergies to Ingredients. People who are allergic to any of the following should not use iohexol.

  • Iohexol
  • Omnipaque
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific iohexol products they stock.

Certain Procedure Restrictions. Iohexol should not be used for a hysterosalpingogram (HSG), which is a special X-ray of the uterus and fallopian tubes, in the following situations.

  • If you are pregnant or might be pregnant
  • If you have your period or it is about to start
  • Within 6 months after a pregnancy ends
  • Within 30 days after a cone biopsy or curettage procedure
  • If you have an infection or cancer in any part of your genital area or reproductive organs

What should I know about iohexol before using it?

Iohexol is usually given by a health care provider in a hospital or clinic. Follow any instructions given by your health care provider.

People who are 65 or older and children under 3 can be at greater risk for some side effects from iohexol. Talk to your health care provider about the risks if you are in one of these age groups.

What should I tell my health care provider before using iohexol?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if iohexol is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

Lab Tests. Iohexol can affect the results of certain lab tests, including some thyroid tests and tests using radioactive iodine. Tell all of your health care providers if you have any lab tests or blood work planned.

Other Medicines and Supplements. Iohexol may interact with other medicines and supplements. Before using iohexol, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. If you are pregnant or may be pregnant, iohexol should not be used for a hysterosalpingogram (HSG) procedure (a special X-ray of the uterus and fallopian tubes) due to the risk of harm to an unborn baby. For other imaging scans, it is not known if or how iohexol could affect pregnancy or harm an unborn baby. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. Iohexol may pass into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed. Your health care provider will let you know if you should use iohexol while breastfeeding.

Interactions

Does iohexol interact with foods or drinks?

Your health care provider may tell you to avoid eating or drinking for a few hours before your scan. Iohexol will be given to you before your scan.

It is unknown if drinking alcohol will affect iohexol.

Does iohexol interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before using iohexol.

  • Metformin (Fortamet, Glumetza, and others), which is a medicine for diabetes
  • A diuretic, also called a water pill, which is a medicine used to reduce edema (fluid retention) and blood pressure
  • A laxative, which may be used to treat constipation
  • A medicine that may harm the kidneys, such as certain antibiotics

This may not be a complete list of medicines that can interact with iohexol. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much iohexol?

If you or someone else has used too much iohexol, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of iohexol?

Iohexol is usually given by a health care provider in a hospital or clinic. Your health care provider will make sure you are receiving iohexol as scheduled.