Firazyr (icatibant) is a prescription drug that’s used to treat sudden swelling caused by hereditary angioedema. Firazyr can cause side effects that range from mild to serious. Examples include rash and dizziness.

Specifically, Firazyr is used in adults to treat sudden episodes of severe swelling caused by hereditary angioedema (HAE).

Note: Using Firazyr to stop a swelling episode in your throat may not completely prevent your airway from being blocked. So after using Firazyr for a swelling episode in your throat, take steps to help prevent a life threatening episode. Seek immediate medical attention or call 911 right away.

The active ingredient in Firazyr is icatibant. (An active ingredient is what makes a drug work.) The drug comes as a liquid for injection under the skin.

Keep reading to learn about the common, mild, and serious side effects that Firazyr can cause. For a general overview of the drug, including details about its uses, see this article.

Some people may experience mild to serious side effects during their Firazyr treatment. Examples of the drug’s commonly reported side effects include:

To learn more about injection site reaction and elevated liver enzymes, see the “Side effects explained” section below.

Mild side effects have been reported with Firazyr. These include:

In most cases, these side effects should be temporary. And some may be managed easily. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop using Firazyr unless your doctor recommends it.

Firazyr may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

To learn more about the following side effects, see the “Side effects explained” section below:

  • injection site reactions
  • elevated liver enzymes
  • mild allergic reaction

No serious side effects were reported during Firazyr studies.

As with any medication, a severe allergic reaction is possible with Firazyr, but it wasn’t reported in studies. To learn more about this side effect, see the “Side effects explained” section below.

If you develop serious side effects while using Firazyr, call your doctor right away. If the side effects seem life threatening or you think you have a medical emergency, immediately call 911. Or call your local emergency number.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Firazyr, visit MedWatch.

Get answers to some frequently asked questions about Firazyr’s side effects.

Does taking an angiotensin converting enzyme (ACE) inhibitor increase my risk of side effects?

Taking an ACE inhibitor with Firazyr will not increase your risk of side effects. Instead, Firazyr can block the effectiveness of your ACE inhibitor. In turn, this may increase your blood pressure and fluid swelling, worsen kidney function, or trigger heart failure.

It’s also essential to know that ACE inhibitors can trigger HAE episodes. Because of this, people with confirmed HAE should avoid taking ACE inhibitors.

If you use an ACE inhibitor, talk with your doctor before you start using Firazyr.

Will Firazyr injections impair my ability to drive?

You may feel dizzy, drowsy, or tired after a Firazyr injection. This can affect your alertness. So it’s best to avoid driving or operating machinery after a Firazyr injection.

If you have questions about Firazyr affecting your alertness, check with your doctor or pharmacist.

Does Firazyr cause long-term side effects?

It’s unlikely that Firazyr will cause long-term side effects because you use it only as needed. Your body will clear most of a Firazyr dose within 4–9 hours after an injection.

Further, long-term side effects weren’t reported in studies of Firazyr.

If you’re concerned about possible long-term side effects from Firazyr, talk with your doctor or pharmacist.

Learn more about some of the side effects Firazyr may cause.

Injection site reaction

Injection site reaction was the most common side effect reported in studies of Firazyr. It affected 3 of 4 people. Injection site reaction may cause symptoms such as:

  • itching
  • feeling of pressure
  • warmth at the injection area
  • blood blister
  • welts
  • burning
  • swelling
  • redness or deepened skin color
  • bruising
  • numbness
  • irritation
  • pain

What might help

You can help reduce injection site reaction when using this drug. To do so:

  • choose an injection area at least 2 inches away from any scars and 4 inches below the belly button
  • choose a different site for each injection
  • avoid rubbing the injection site vigorously

If you have an injection site reaction with Firazyr, consider the following options to help relieve your symptoms:

  • apply a cool compress to the area
  • take over-the-counter (OTC) acetaminophen for pain
  • apply OTC hydrocortisone cream for itching or burning

Talk with your doctor if your symptoms worsen. Also tell them if you develop a fever or drainage at the injection site lasting longer than 24 hours. In either case, it’s likely they will suggest an office visit to determine whether you have an infection.

Elevated liver enzymes

Elevated liver enzymes called transaminases were an uncommon and mild side effect reported in studies of Firazyr. No serious problems with elevated transaminases or liver problems occurred during Firazyr research.

What might help

It’s unlikely that you’d have symptoms from elevated transaminases. But if you need to use Firazyr frequently, your doctor may order blood work regularly to review this.

If you have concerns about developing elevated transaminases during Firazyr treatment, talk with your doctor or pharmacist.

Allergic reaction

Like most drugs, Firazyr can cause an allergic reaction in some people. But this side effect wasn’t reported in studies.

Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin (usually in your eyelids, lips, hands, or feet)
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:

  • an oral antihistamine, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

Your doctor can confirm whether your allergic reaction to Firazyr is mild. If it is, they’ll decide whether you should continue using it.

Watch for symptoms of a severe allergic reaction, such as swelling or difficulty breathing. If you develop these, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

Your doctor can confirm whether you’ve had a serious allergic reaction to Firazyr. If you have, they may switch your treatment.

Keeping track of side effects

During your Firazyr treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start a new drug or combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were using when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Firazyr affects you. They can then use this information to adjust your treatment plan if needed.

Below is important information you should consider before using Firazyr.


Firazyr can sometimes cause harmful effects in people who have certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether this drug is a good treatment option for you.

Talk with your doctor about your health history before using Firazyr. Be sure to tell them if any of the following factors apply to you:

  • history of HAE episodes of sudden throat swelling
  • use of ACE inhibitors
  • use of other medications, over-the-counter drugs, vitamins, supplements, or herbs
  • past allergic reaction to Firazyr
  • pregnancy
  • breastfeeding

Alcohol and Firazyr

No interactions between alcohol and Firazyr are known. Yet, drinking alcohol may increase the risk of HAE episodes. For this reason, it’s best to consult with your doctor or pharmacist. They can determine whether it’s safe for you to drink alcohol while using Firazyr.

Pregnancy and breastfeeding with Firazyr

Before starting Firazyr treatment, it’s important to talk with your doctor if you’re pregnant, breastfeeding, or planning either.


It’s not known whether it’s safe to use Firazyr during pregnancy. If you’re pregnant or planning to become pregnant, talk with your doctor before starting treatment with Firazyr.

If you’re able to become pregnant, your doctor may recommend using a form of birth control during your Firazyr treatment. They’ll likely recommend using it for a certain amount of time before starting Firazyr and throughout your treatment. You may also need to continue using birth control for some time after your Firazyr treatment ends.


It isn’t known whether Firazyr is safe to use while breastfeeding. If you’re breastfeeding or planning to do so, talk with your doctor before starting this medication.

Like most drugs, Firazyr can cause a number of side effects that range from mild to serious. Some are temporary and go away after a few days to weeks. Others may be longer lasting. If you have questions about side effects that Firazyr can cause, talk with your doctor.

Examples of questions to help get you started include:

  • While using Firazyr injections, what is my risk of having increased liver enzymes?
  • Will I always develop an injection site reaction after a dose of Firazyr?
  • What side effects of Firazyr should prompt me to call you?

To learn more about Firazyr, see this “Firazyr (icatibant acetate)” article.

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.