Haegarda (C1 esterase inhibitor [human]) is a prescription drug used to help prevent hereditary angioedema (HAE) attacks. Haegarda can cause side effects that range from mild to serious. Examples include injection site reaction, dizziness, and skin rash.

Specifically, Haegarda is used to help prevent rapid and painful swelling in people ages 6 years and older with HAE.

Haegarda is a biologic drug, which means it’s made from living cells. It contains the active ingredient C1 esterase inhibitor. (An active ingredient is what makes a drug work.) The drug comes as a powder in vials. The powder is mixed with sterile water and this liquid solution is then injected under your skin.

Keep reading to learn about common, mild, and serious side effects Haegarda 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 Haegarda treatment. Examples of the drug’s commonly reported side effects include:

* To learn more about this side effect, see the “Side effects explained” section below.

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

  • dizziness
  • nasopharyngitis (stuffy or runny nose, sneezing, watery eyes)*
  • injection site reaction*
  • mild allergic reaction (including skin rash, itchy skin)*

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

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

* To learn more about this side effect, see the “Side effects explained” section below.

Serious side effects have been reported with Haegarda, including severe allergic reaction. To learn more about this side effect, see the “Side effects explained” section below.

If you develop serious side effects during Haegarda treatment, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or 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 Haegarda, visit MedWatch.

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

How do side effects of Haegarda compare with those of Berinert or Ruconest?

Haegarda, Berinert, and Ruconest all contain C1 esterase inhibitor as an active ingredient. Side effects like an allergic reaction and a runny or stuffy nose are commonly reported with these medications.

In studies of Berinert, altered taste and a higher pain intensity associated with HAE swelling were also reported. These side effects were not reported in studies of Haegarda.

Talk with your doctor or pharmacist if you have questions about how side effects of these drugs compare.

Can Haegarda increase my risk of blood clots?

It’s possible. Studies have not confirmed a relationship between blood clot development and Haegarda use. But Haegarda does affect the body’s blood clotting pathways.

Blood clots have been reported at higher doses when the drug was used to help prevent or treat capillary leak syndrome. But Haegarda is not approved at these higher doses or for treating capillary leak syndrome.

Blot clot symptoms can include:

  • pain and/or swelling of your arm or leg, with warmth in the painful or swollen area
  • change in color of an arm or leg
  • difficulty breathing
  • chest pain or pain that gets worse with deep breathing
  • fast heart rate
  • numbness or weakness on one side of your body

If you have questions about your risk of developing blood clots with Haegarda, talk with your doctor.

Can Haegarda increase my risk of infection?

Yes. Because Haegarda is made from human blood and proteins, it can increase the risk of infection in your blood. However, this risk is lowered by screening and testing donors and their blood for viruses. Processes used to remove certain viruses are also included when the drug is made.

If you have questions about your risk of infection from Haegarda, talk with your doctor.

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

Injection site reactions

Injection site reactions were a common side effect reported in studies of Haegarda. This side effect may cause symptoms around the injection site, such as pain, redness or skin discoloration, itchiness, and skin thickening.

Factors that can raise the risk of injection site reactions with this drug include:

  • injecting Haegarda that’s colder than room temperature
  • not rotating the injection site

What might help

Be sure to rotate the site where you inject Haegarda, and allow the drug to reach room temperature for 30 minutes before you inject it.

If you still experience injection site reactions, talk with your doctor. They can suggest ways to help lower your symptoms, such as by applying a cool compress on tender or discolored areas.

Nasopharyngitis

Nasopharyngitis was a common side effect reported in studies of Haegarda. This side effect may cause symptoms such as:

  • runny or stuffy nose
  • sneezing
  • watery eyes

Factors that can increase the risk of nasopharyngitis with this drug include:

What might help

If you notice any of the above symptoms during Haegarda treatment, talk with your doctor. If it’s not an infection, they’ll likely recommend:

Allergic reaction

Like most drugs, Haegarda can cause an allergic reaction in some people. And this side effect was 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

If your doctor confirms you’ve had a mild allergic reaction to Haegarda, they’ll decide whether you should continue treatment.

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

If your doctor confirms you’ve had a serious allergic reaction to Haegarda, they may have you switch to a different treatment.

Keeping track of side effects

During your Haegarda 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 taking 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

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

Below is important information you should consider before starting Haegarda.

Warnings

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

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

  • blood clots
  • past allergic reaction to Haegarda or similar drugs like Berinert and Ruconest
  • pregnancy
  • breastfeeding

Alcohol and Haegarda

There are no known interactions between alcohol and Haegarda. If you have questions about consuming alcohol during Haegarda treatment, talk with your doctor or pharmacist.

Pregnancy and breastfeeding with Haegarda

There’s limited information about the safety of Haegarda use during pregnancy or while breastfeeding.

Pregnancy

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

Breastfeeding

It isn’t known whether Haegarda 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, Haegarda can cause a number of side effects that range from mild to serious. But most are temporary and go away after a few days to weeks. If you have questions about side effects Haegarda can cause, talk with your doctor. Examples of questions to help get you started include:

  • When should I contact you about side effects I’m having with Haegarda?
  • Does my risk of developing blood clots depend on my dosage?
  • Will the side effects of Haegarda resolve over time?

To get information on different conditions and tips for improving your health, subscribe to any of Healthline’s newsletters. You may also want to check out the online communities at Bezzy. It’s a place where people with certain conditions can find support and connect with others.

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.