Firazyr (Icatibant)

What Is Firazyr and What Is It Used For?

Firazyr (icatibant) is a bradykinin B2 receptor antagonist used to treat acute attacks of hereditary angioedema (HAE) in adults, adolescents, and children aged 2 years and older. It works by blocking the action of bradykinin, the key mediator responsible for the swelling and pain experienced during HAE attacks.

Hereditary angioedema (HAE) is a rare genetic disorder caused by a deficiency or dysfunction of C1-esterase inhibitor (C1-INH), a protein that normally helps regulate the kallikrein-kinin system. When C1-INH is absent or insufficient, the kallikrein-kinin cascade becomes overactive, leading to excessive production of bradykinin. This powerful vasoactive peptide increases vascular permeability and causes fluid to leak from blood vessels into surrounding tissues, resulting in unpredictable episodes of severe swelling (angioedema).

HAE attacks can affect virtually any part of the body. The most commonly affected areas include the face (lips, eyelids, tongue), extremities (hands and feet), abdominal organs (causing intense abdominal pain, nausea, vomiting, and diarrhoea), and the upper airway (larynx and throat). Laryngeal attacks are the most dangerous, as swelling of the throat can obstruct the airway and become life-threatening if not treated promptly. According to international epidemiological data, HAE affects approximately 1 in 50,000 people worldwide, though it is likely underdiagnosed due to the rarity of the condition and overlap with other causes of angioedema.

Firazyr contains the active substance icatibant, a synthetic decapeptide that acts as a selective, competitive antagonist at the bradykinin B2 receptor. By occupying the B2 receptor, icatibant prevents endogenous bradykinin from binding and triggering the signalling cascade that leads to vasodilation, increased vascular permeability, and oedema formation. Unlike C1-INH replacement therapies, which work upstream by restoring the regulatory balance, icatibant blocks the final effector pathway directly at the receptor level.

Firazyr was first approved by the European Medicines Agency (EMA) in 2008 and by the United States Food and Drug Administration (FDA) in 2011. It represented a significant advance in HAE management because it was the first bradykinin receptor antagonist approved for this indication, offering a novel mechanism of action. The medication is now available from multiple manufacturers as both the original branded product and several generic formulations.

What Should You Know Before Taking Firazyr?

Before using Firazyr, inform your doctor about all medical conditions, especially ischaemic heart disease (angina) and recent stroke. The first injection must always be given by a healthcare professional. Patients should be trained in self-injection technique before administering Firazyr at home.

Contraindications

You should not use Firazyr if you are allergic to icatibant or any of the other ingredients in this medicine. The excipients include sodium chloride, glacial acetic acid, sodium hydroxide, and water for injections. If you have previously experienced an allergic reaction to icatibant or to any other component of the formulation, inform your doctor immediately.

Warnings and Precautions

Talk to your doctor before using Firazyr if any of the following apply to you:

• Ischaemic heart disease (angina pectoris) – reduced blood flow to the heart muscle may be affected by changes in bradykinin signalling. Firazyr should be used with caution in patients with coronary artery disease
• Recent stroke – patients who have recently experienced a cerebrovascular event should exercise particular caution, as bradykinin plays a complex role in vascular regulation

Some side effects of Firazyr can resemble the symptoms of an HAE attack. If you notice that your symptoms worsen after receiving Firazyr, or if new symptoms develop, contact your doctor immediately. It is important to distinguish between injection-site reactions (which are very common and usually mild) and worsening of the underlying HAE episode.

Self-Injection Training

If you have never received Firazyr before, your first dose must be administered by a doctor or nurse. Your healthcare professional will observe you after the injection to ensure there are no adverse reactions. Once your doctor is satisfied that you can safely self-administer the medication, they will provide comprehensive training in subcutaneous injection technique. This training covers proper hand hygiene, preparation of the syringe and needle, selection and cleaning of the injection site, correct injection technique, and safe disposal of used materials.

Your doctor will also instruct your caregiver in the injection procedure, so that another person can administer Firazyr if you are unable to self-inject during a severe attack. It is essential that both you and your caregiver practice the technique until you are confident and comfortable with the procedure.

Additional Injections

If your symptoms have not improved after 6 hours following the first injection, seek medical advice regarding additional injections. For adult patients, up to two additional injections may be given within a 24-hour period, for a maximum of three injections (90 mg) per 24 hours. If you require more than 8 injections in any given month, consult your doctor to discuss your treatment plan and whether prophylactic therapy should be considered.

Children and Adolescents

Firazyr is approved for use in children and adolescents aged 2 years and older who weigh at least 12 kg. The dose is calculated based on body weight (see the dosage section below). Firazyr is not recommended for children under 2 years of age or for those weighing less than 12 kg, as clinical studies have not been conducted in this population. In paediatric patients, the injection should be given by a trained caregiver or healthcare professional.

Pregnancy and Breastfeeding

If you are pregnant, think you might be pregnant, or are planning to have a baby, ask your doctor for advice before using Firazyr. The safety of icatibant during pregnancy has not been fully established in humans. Animal reproductive studies have not shown direct harmful effects, but as a precautionary measure, Firazyr should only be used during pregnancy if the potential benefit justifies the potential risk to the foetus. Your doctor will carefully evaluate the risks and benefits before prescribing Firazyr during pregnancy.

If you are breastfeeding, you should not breastfeed for 12 hours after receiving the most recent injection of Firazyr. This precaution is based on the possibility that icatibant or its metabolites may pass into breast milk. After the 12-hour window, breastfeeding may be safely resumed.

Driving and Operating Machinery

Do not drive or operate machinery if you feel tired or dizzy following an HAE attack or after administering Firazyr. Both the HAE attack itself and the medication can cause fatigue and dizziness. Wait until these symptoms have fully resolved before driving or engaging in activities that require alertness and coordination.

Drug Interactions

Firazyr has no known clinically significant pharmacokinetic drug interactions. However, patients taking ACE inhibitors should inform their doctor, as Firazyr may theoretically reduce the antihypertensive effect of these medications.

Icatibant is metabolised by proteolytic enzymes and does not inhibit or induce cytochrome P450 (CYP) enzymes. As a result, it is unlikely to interact with medications that are metabolised through the CYP enzyme system. No formal drug-drug interaction studies have identified clinically important interactions with Firazyr.

However, there is a theoretical interaction with ACE inhibitors (angiotensin-converting enzyme inhibitors) such as captopril, enalapril, ramipril, quinapril, and lisinopril. Both ACE inhibitors and icatibant affect the bradykinin pathway: ACE inhibitors increase bradykinin levels (which contributes to their blood pressure-lowering effect), while icatibant blocks the bradykinin B2 receptor. Using Firazyr concurrently with an ACE inhibitor may theoretically reduce the antihypertensive efficacy of the ACE inhibitor. If you take an ACE inhibitor for high blood pressure or any other reason, be sure to inform your doctor before using Firazyr.

Sodium Content

Firazyr injection solution contains less than 1 mmol (23 mg) sodium per syringe. This means it is essentially sodium-free, which is relevant for patients on a sodium-restricted diet.

What Is the Correct Dosage of Firazyr?

The recommended adult dose of Firazyr is one 30 mg injection (3 ml) given subcutaneously as soon as an HAE attack develops. For children and adolescents aged 2–17 years, the dose is weight-based, ranging from 1 ml to 3 ml. Up to 3 injections may be given within 24 hours for adults.

Always use Firazyr exactly as your doctor has instructed. Inject Firazyr as soon as you recognise the early signs of an HAE attack. Early treatment leads to faster symptom resolution. If you are unsure about the correct dose or injection technique, consult your doctor, pharmacist, or nurse.

Adults (18 years and older)

Children and Adolescents (2–17 years)

The dose for paediatric patients is based on body weight. For children weighing 65 kg or less, the required volume must be drawn from the pre-filled syringe into a graduated syringe using the supplied adapter. Children weighing more than 65 kg receive the full adult dose.

If symptoms worsen or do not improve, the child must be taken to a doctor immediately. Only healthcare professionals should determine whether additional injections are needed for paediatric patients.

How to Inject Firazyr

Firazyr is administered as a subcutaneous injection (under the skin) into the fatty tissue of the abdomen. Each pre-filled syringe is for single use only. Follow these steps:

1. Prepare: Wash your hands thoroughly with soap and water. Clean your work surface. Remove the pre-filled syringe from its packaging and unscrew the protective cap.
2. For paediatric patients (65 kg or less): Use the supplied adapter and graduated syringe to transfer the required volume from the pre-filled syringe. Ensure no air bubbles remain in the graduated syringe.
3. Attach the needle: Remove the needle guard from the blister pack, break the seal, and carefully attach and screw the needle onto the syringe while the needle remains in the guard. Pull the syringe to remove the needle from the guard.
4. Choose the injection site: Select a site on the abdomen approximately 5–10 cm below the navel on either side. Avoid areas that are scarred, bruised, swollen, or painful. The site must be at least 5 cm from any scar tissue.
5. Clean the site: Swab the injection site with an alcohol wipe and allow it to dry completely.
6. Inject: Hold the syringe at a 45–90 degree angle. Pinch a fold of skin at the injection site. Insert the needle and push the plunger slowly and steadily over approximately 30 seconds until all the solution has been injected. Release the skin fold and gently withdraw the needle.
7. Dispose: Place the used syringe, needle, and guard into a sharps disposal container immediately. Do not recap the needle.

What Are the Side Effects of Firazyr?

The most common side effects of Firazyr are injection-site reactions, which occur in nearly all patients. These include redness, swelling, pain, itching, and a burning sensation at the injection site. These reactions are generally mild and resolve without treatment.

Like all medicines, Firazyr can cause side effects, although not everybody gets them. Almost all patients who receive Firazyr experience some form of injection-site reaction. These local reactions are expected and are not a reason to stop using the medication. They typically resolve within a few hours without any additional treatment.

It can sometimes be difficult to distinguish between side effects of Firazyr and the symptoms of your HAE attack. If you are uncertain whether your symptoms are caused by the medication or the underlying disease, contact your healthcare provider for advice. Importantly, if you notice that your attack symptoms are getting worse after the injection, tell your doctor immediately.

If you experience any side effects not listed here, or if any side effect becomes severe or persistent, contact your doctor or pharmacist. Reporting suspected side effects helps regulatory agencies monitor the benefit-risk balance of medicines and ensures patient safety.

How Should You Store Firazyr?

Store Firazyr at or below 25°C (77°F). Do not freeze. Keep out of the reach and sight of children. Do not use after the expiry date or if the solution appears cloudy or discoloured.

Keep the pre-filled syringe in its original packaging to protect it from light. Do not remove the syringe from the packaging until you are ready to use it. Before each use, visually inspect the solution through the glass barrel of the syringe. The solution should be clear and colourless. Do not use Firazyr if the solution appears cloudy, contains floating particles, or has changed colour.

Check the expiry date on the label (marked "EXP") before each use. The expiry date refers to the last day of the stated month. Do not use the syringe if the packaging or syringe is damaged.

Because HAE attacks are unpredictable, it is strongly recommended that you carry Firazyr with you at all times. When travelling, store the medication in a cool bag if temperatures may exceed 25°C. Avoid leaving the syringe in direct sunlight, in a hot car, or near a heat source.

Do not flush unused medication down the toilet or throw it in household waste. Return any unused or expired syringes to your pharmacy for safe disposal. These measures help protect the environment from pharmaceutical contamination.

What Does Firazyr Contain?

Each pre-filled syringe of Firazyr contains 30 mg of icatibant (as acetate) in 3 ml of clear, colourless solution. The other ingredients are sodium chloride, glacial acetic acid, sodium hydroxide, and water for injections.

Active Ingredient

The active substance is icatibant. Each pre-filled syringe contains 30 milligrams of icatibant (as acetate) dissolved in 3 ml of solution, giving a concentration of 10 mg/ml. Icatibant is a synthetic decapeptide (a chain of 10 amino acids) that structurally resembles bradykinin but has been modified to act as a competitive antagonist rather than an agonist at the B2 receptor.

Inactive Ingredients (Excipients)

The other ingredients are:

• Sodium chloride – helps to maintain the osmolarity of the solution, making it isotonic with body fluids to reduce discomfort at the injection site
• Glacial acetic acid – used as a pH buffer to maintain the stability of the solution
• Sodium hydroxide – used for pH adjustment
• Water for injections – the solvent in which the active ingredient and excipients are dissolved

Sodium Content

This medicine contains less than 1 mmol (23 mg) sodium per syringe, meaning it is essentially sodium-free.

Presentation and Packaging

Firazyr is a clear, colourless solution for injection supplied in a pre-filled glass syringe (3 ml). An injection needle is included in the packaging. Firazyr is available as a single pack containing one pre-filled syringe and one injection needle, or as a multipack containing three pre-filled syringes and three injection needles. Not all pack sizes may be marketed in every country.

Marketing Authorisation Holder

Firazyr is marketed by Takeda Pharmaceuticals and is also available as generic icatibant from several manufacturers, including Icatibant STADA, Icatibant Avansor, Icatibant Newbury, Icatibant Teva, Icatibant Medical Valley, Icatibant Accord, and Icatibant Glenmark. All authorised formulations contain the same active ingredient and are therapeutically equivalent.

How Does Firazyr Work in the Body?

Firazyr works by selectively blocking the bradykinin B2 receptor. In HAE patients, excess bradykinin causes blood vessels to leak fluid, leading to swelling. By blocking the receptor, icatibant prevents bradykinin from triggering vasodilation and increased vascular permeability, thereby reversing the oedema.

To understand how Firazyr works, it is helpful to understand the bradykinin pathway and its role in hereditary angioedema. The kallikrein-kinin system is a complex cascade of enzymes and proteins that plays a role in inflammation, blood pressure regulation, and pain signalling. In healthy individuals, this system is tightly regulated by C1-esterase inhibitor (C1-INH).

In patients with HAE types I and II, there is either a quantitative deficiency (type I, approximately 85% of cases) or a functional deficiency (type II, approximately 15% of cases) of C1-INH. Without adequate C1-INH, the enzyme plasma kallikrein becomes overactive and cleaves high-molecular-weight kininogen to release bradykinin. Bradykinin binds to B2 receptors on endothelial cells lining the blood vessels, activating intracellular signalling pathways that lead to nitric oxide and prostacyclin release. These mediators cause vasodilation (widening of blood vessels) and increased vascular permeability (leakage of fluid from blood vessels into surrounding tissues), resulting in the characteristic oedema of HAE.

Icatibant is a synthetic peptide that has been specifically designed to bind to the bradykinin B2 receptor with high affinity but without activating it. By occupying the receptor, icatibant competitively blocks endogenous bradykinin from binding. This directly prevents the downstream signalling that causes vasodilation and fluid leakage, thereby reducing swelling and associated symptoms such as pain and nausea.

Pharmacokinetic Profile

After subcutaneous injection, icatibant is rapidly absorbed, reaching peak plasma concentrations within approximately 30 minutes. The absolute bioavailability of the subcutaneous route is approximately 97%, meaning nearly all of the injected dose reaches the systemic circulation. Icatibant is distributed with a volume of distribution of approximately 29 litres.

Icatibant is metabolised primarily by proteolytic enzymes into inactive metabolites. Importantly, it does not interact with cytochrome P450 enzymes, which minimises the risk of drug-drug interactions. The elimination half-life is approximately 1–2 hours, and the drug is primarily excreted via the kidneys (approximately 73% as metabolites). Despite its short half-life, clinical studies demonstrate sustained symptom relief lasting well beyond the plasma half-life, suggesting that receptor occupancy and downstream effects persist after the drug has been cleared from the blood.

The rapid onset of action (within approximately 30 minutes of injection) combined with high bioavailability makes subcutaneous icatibant particularly well suited for acute, on-demand treatment of HAE attacks, where timely intervention is critical for minimising morbidity and preventing potentially life-threatening complications.

Frequently Asked Questions About Firazyr