Hereditary Angioedema (HAE): When and How to Use On-Demand (Acute) Medications
Updated on May 13, 2026
ON THIS PAGE
ON THIS PAGE
On-demand or acute treatment for hereditary angioedema (HAE) attacks is crucial for getting your symptoms under control quickly. In some cases, it could even be lifesaving. Here’s what you need to know about when and how to use your prescribed on-demand treatment, as well as when to seek emergency medical care.
Identifying Attack Symptoms
Spotting symptoms of an HAE attack is the first step toward stopping it as soon as possible. Common signs can include:
- Swelling in the hands, feet, eyelids, lips, or genitals
- Sudden, severe abdominal pain
- Nausea or vomiting
- Signs of airway swelling, such as trouble speaking or swallowing, mouth or tongue swelling, or noisy breathing
These symptoms occur because HAE increases an individual’s vascular permeability, causing the blood vessels to leak fluid into other tissues in the body that results in uncomfortable swelling, says Andrew Macginnitie, MD, an allergist and immunologist with Children’s Wisconsin in Milwaukee.
Some people with HAE also notice symptoms before an attack actually starts. Referred to as prodromal symptoms, they can appear up to a few hours before an attack and serve as early warning signs. These symptoms can include:
- Erythema marginatum, a pink-red, ring-like rash that doesn’t itch
- Fatigue
- Mood changes
- Nausea or abdominal pain
- Tingling
An HAE attack or prodromal symptoms can occur in response to certain triggers, such as stress, a cold or infection, minor trauma or surgery, or repetitive hand motion as with prolonged typing, writing, or tool use. But that’s not always the case.
“Often, attacks aren’t triggered by anything — they just occur,” says Timothy Craig, DO, an allergist and immunologist with Penn State Health in Hershey, Pennsylvania.
When to Treat an Attack
Take your on-demand medications as soon as you start to notice symptoms of an HAE attack. Treating it sooner will stop your symptoms from worsening, which can reduce your risk of life-threatening throat or airway swelling.
Be prepared by keeping two doses of your on-demand medications with you at all times. “Think of on-demand treatment like an EpiPen for people with food allergies,” says Dr. Craig.
As for prodromal symptoms that tell you an HAE attack may be on the way, experts typically recommend waiting until an attack begins to take your medication. But some people with very clear prodromal symptoms may decide alongside their doctors that taking their on-demand medications before an attack actually strikes is the right move, says Dr. Macginnitie. “There isn’t great data, so it really has to be individualized,” he says.
How to Use On-Demand Medications for HAE
There are five U.S. Food and Drug Administration (FDA)–approved on-demand medications for HAE. All are intended to be self-administered (or administered by a parent or caregiver) so you can get the medication into your system as quickly as needed.
“Your care team should walk you through how to take your medication,” says Craig. These medications can require some complicated techniques, so don’t be afraid to ask questions during your appointments if something is unclear.
How you administer your medication depends on which one your doctor prescribes.
C1-Inhibitors (C1-INH)
Human C1-esterase inhibitor (Berinert) and conestat alfa (Ruconest) increase the body’s levels of C1-INH, a protein that helps control swelling, inflammation, and vascular permeability. These medications are injected intravenously to deliver C1-INH directly into your bloodstream. The process is tricky, so you need detailed instruction before doing it at home.
First, reconstitute the medication by injecting sterile water into the glass vial containing powdered medicine. Gently swirl the vial on a flat surface until it clears, readying the medicine for infusion. With training from your medical team, you will learn how to prime a syringe and locate a vein in your arm or hand. Once you've successfully punctured the vein, perform a slow IV push, manually pressing the plunger to deliver the medication at a steady rate.
Kallikrein Inhibitors
Kallikrein inhibitors like ecallantide (Kalbitor) and sebetralstat (Ekterly) work by blocking kallikrein, an enzyme that causes blood vessels to widen and leak, thereby reducing swelling and inflammation during an HAE attack.
Kalbitor is injected subcutaneously into the abdomen, thigh, or upper arm. Using a large bore needle and syringe, withdraw 1 milliliter (mL) of the liquid medication from the medication vial. Then, switch out the large bore needle for an injection needle on the syringe, clean your chosen injection site with an alcohol swab, and inject the dose until the syringe is completely empty. Repeat this procedure until you’ve dosed the amount of the medication your doctor prescribes. You don’t need to rotate injection sites, but you should separate each injection site by at least 2 inches and avoid giving injections in areas where you’re having an attack.
Ekterly is the first and only oral on-demand HAE medication approved for treating acute attacks in people ages 12 and older. It’s available in a 300 milligram (mg) tablet. At the very first sign of an acute attack, take two tablets by mouth (for a total dose of 600 mg). If your symptoms don’t improve, or if they worsen or return, you can take a second 600 mg dose at least three hours after your first dose, up to a maximum dosage of 1,200 mg in any 24-hour period.
Bradykinin B2 Receptor Agonists
Icatibant (Firazyr) is a bradykinin B2 receptor agonist that stops HAE attacks by blocking bradykinin, the peptide that triggers rapid swelling and abdominal pain.
Firazyr is injected subcutaneously into the abdomen. Take the cap off the prefilled syringe and replace it with the needle from the needle cap. Clean your injection site with an alcohol swab, gently pinch the skin to make a fold, and slowly inject the medication until the syringe is completely empty.
Post-Attack Management
On-demand treatments start working right away to prevent your attack from worsening, says Macginnitie. But depending on your medication, it may take 30 minutes to two hours to start noticing an improvement in symptoms like swelling.
What you should do in the meantime depends on your symptoms. You can return to your normal activities if you feel up to it, but rest or an over-the-counter pain reliever like ibuprofen or acetaminophen can be helpful if you’re uncomfortable, says Macginnitie.
If your symptoms don’t start to improve within the expected timeframe, you may need to take a second dose of your medication. Check the prescription information for your medication to determine when you should take a second dose. If the second dose doesn’t seem to help, contact your doctor or seek emergency medical attention for life-threatening symptoms.
When to Call 911
HAE attacks can be life-threatening when they cause swelling of the throat or airway. Seek emergency medical care right away if you or a loved one is experiencing trouble breathing, trouble swallowing, or signs of tongue or throat swelling, even if you’ve administered on-demand treatment at home.
The Takeaway
- Hereditary angioedema (HAE) causes sudden swelling or severe abdominal pain due to increased vascular permeability. It’s essential to identify the early warning signs of an attack to manage it effectively.
- Experts recommend administering on-demand medications as soon as an attack begins to prevent symptoms from worsening, and you should keep two doses of your prescribed treatment accessible at all times.
- FDA-approved acute treatments include C1-inhibitors, which are administered intravenously, kallikrein inhibitors (one subcutaneous injection and one oral tablet), and bradykinin B2 receptor agonists, which are injected subcutaneously.
- It’s critical to seek emergency medical care immediately if swelling affects your throat or airway, leading to difficulty breathing or swallowing.
Resources We Trust
- Mayo Clinic: On-Demand and Preventive Medicines: Understanding Treatment Options for Hereditary Angioedema
- Cleveland Clinic: Hereditary Angioedema Attacks: Triggers and Treatment 101
- US Hereditary Angioedema Association: Approved HAE Treatments
- HAE International: Live Life Effectively Free From Swellings
- American Academy of Allergy, Asthma and Immunology: Treatment of Hereditary Angioedema
EDITORIAL SOURCES
Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.
Resources
- Hereditary Angioedema. National Organization for Rare Disorders. January 6, 2025.
- Leibovich-Nassi I et al. The Enigma of Prodromes in Hereditary Angioedema (HAE). Clinical Reviews in Allergy & Immunology. August 2021.
- Lochbaum R et al. Analysis of Prodromal Symptoms and Need for Short-Term Prophylaxis in Angioedema Patients Under Long-Term Prophylaxis. Orphanet Journal of Rare Diseases. February 1, 2025.
- What Is Hereditary Angioedema (HAE)? US Hereditary Angioedema Association.
- Busse P et al. US HAEA Medical Advisory Board 2020 Guidelines for the Management of Hereditary Angioedema. The Journal of Allergy and Clinical Immunology: In Practice. 2021.
- C1-Esterase Inhibitor Human Injection. MedlinePlus. March 15, 2022.
- Berinert Self-Administration Guide. CSL Behring.
- Kalbitor. European Medicines Agency. February 9, 2012.
- Kalbitor Prescribing Information. Takeda Pharmaceutical Company. June 2025.
- Sebetralstat (Oral Route). Mayo Clinic. March 31, 2026.
- Icatibant Injection. MedlinePlus. September 15, 2023.
- Firazyr Prescribing Information. Takeda Pharmaceutical Company. June 2025.
- Hereditary Angioedema. Cleveland Clinic. March 31, 2025.
Meet Our Experts
Stephen H. Kimura, MD
Medical Reviewer
Stephen Kimura, MD, is a board-certified allergist and immunologist. He's been in private practice in Pensacola, Florida, for the past 25 years with the Medical Center Clinic, a mu...
Marygrace Taylor
Author
Marygrace Taylor is an award-winning freelance health and wellness writer with more than 15 years of experience covering topics including women’s health, nutrition, chronic conditi...