Firazyr

The standard, FDA-recommended dose of Icatibant for the treatment of an acute attack of Hereditary Angioedema (HAE) in adults is 30 mg.

• Administration Route: Subcutaneous (SC) injection only.
• Dosing Frequency: If the initial 30 mg dose does not provide adequate relief, or if the symptoms of the HAE attack return after an initial response, additional doses of 30 mg may be administered.
• Interval: There must be at least 6 hours between each injection.
• Maximum Dose: No more than 3 doses (90 mg total) should be administered within any 24-hour period.

In the United States, Icatibant is currently not FDA-approved for use in pediatric patients (children and adolescents under the age of 18). The safety and effectiveness of Icatibant in the pediatric population have not been established by the FDA, although clinical trials in children have been conducted in other regions (such as Europe) where it is approved for children as young as 2 years old. Parents should consult a specialist in HAE (usually an allergist or immunologist) for guidance on treating children.

Renal Impairment

Clinical studies have shown that Icatibant clearance is not significantly affected by kidney function. Therefore, no dosage adjustment is required for patients with renal impairment (kidney disease), including those with severe renal failure.

Hepatic Impairment

Icatibant is metabolized by proteolytic enzymes rather than the liver's cytochrome P450 system. Consequently, impaired liver function does not significantly alter the drug's pharmacokinetics. No dosage adjustment is necessary for patients with hepatic impairment (liver disease).

Elderly Patients

In clinical trials, patients over the age of 65 demonstrated similar safety and efficacy profiles to younger adults. While elderly patients may have a slightly slower clearance of the drug, the difference is not clinically significant, and the standard 30 mg dose is recommended. However, healthcare providers should monitor elderly patients closely for potential side effects due to the general increased sensitivity of this population to medications.

Icatibant is intended for subcutaneous injection into the abdominal area. Follow these steps carefully:

1. 1Preparation: Wash your hands thoroughly with soap and water. Check the expiration date on the syringe and ensure the liquid is clear and colorless. Do not use if the solution is cloudy or contains particles.
2. 2Site Selection: Choose an injection site on your abdomen (stomach area), at least 2 inches away from the belly button. Avoid areas where the skin is bruised, scarred, or irritated.
3. 3Cleaning: Clean the injection site with an alcohol swab and allow it to air dry.
4. 4Injection: Remove the needle cap. Pinch a fold of skin at the cleaned site. Insert the needle at a 45- to 90-degree angle. Push the plunger slowly and steadily until the syringe is empty. This usually takes about 10 to 15 seconds.
5. 5Post-Injection: Withdraw the needle and apply gentle pressure with a gauze pad or cotton ball. Do not rub the area. Dispose of the syringe in a puncture-resistant sharps container.

Storage: Store Icatibant at room temperature (between 36°F and 77°F or 2°C and 25°C). Do not freeze. Keep the syringe in its original carton to protect it from light.

Icatibant is used on an 'as-needed' basis for acute attacks. It is not a daily maintenance medication. Therefore, there is no risk of a 'missed dose' in the traditional sense. However, if you experience an HAE attack and do not have your Icatibant syringe available, you must seek emergency medical care immediately, especially if the swelling involves your throat.

There is limited clinical data regarding Icatibant overdose. In clinical trials, doses up to 90 mg (three times the standard dose) were administered without significant systemic toxicity. However, an overdose would likely result in severe injection site reactions, such as intense pain, swelling, or redness.

If an overdose is suspected, or if multiple doses were taken too close together, contact your healthcare provider or the Poison Control Center immediately. Treatment is supportive, focusing on managing local skin reactions and monitoring for any unusual systemic symptoms.

> Important: Follow your healthcare provider's dosing instructions exactly. Do not adjust your dose or the frequency of administration without explicit medical guidance.

By far the most common side effects of Icatibant are injection site reactions. In clinical trials, almost 97% of patients experienced some form of reaction at the site of the needle insertion. These reactions are typically transient (short-lived) and usually resolve within a few hours, though they can last up to 48 hours in some cases.

• Erythema (Redness): A red patch or rash appearing around the injection site. This is the most frequent reaction.
• Swelling (Edema): Localized puffiness or a 'bump' where the medication was injected.
• Burning or Stinging: A sharp, localized sensation immediately following the injection. This is often described as intense but brief.
• Pruritus (Itching): An itchy sensation at or around the injection site.
• Pain: Mild to moderate soreness in the abdominal tissue where the drug was delivered.

While systemic (body-wide) side effects are less frequent than local reactions, they can still occur. These include:

• Pyrexia (Fever): A slight increase in body temperature shortly after administration.
• Dizziness: A feeling of lightheadedness or unsteadiness. Patients should be cautious when standing up quickly after an injection.
• Headache: Mild to moderate head pain.
• Nausea: A feeling of stomach upset, which is sometimes difficult to distinguish from the symptoms of an abdominal HAE attack.
• Transaminase Elevations: Some patients may show a temporary increase in liver enzymes (ALT or AST) in blood tests. This is usually asymptomatic and resolves without intervention.
• Rash: A generalized skin rash that occurs away from the injection site.

Rarely, patients may experience more unusual symptoms. These may include:

• Asthenia (Weakness): A general feeling of tiredness or lack of energy.
• Hot Flashes: Sudden feelings of warmth, usually in the face or neck.
• Congestion: Nasal stuffiness or a 'stuffy' feeling in the head.

While Icatibant is generally well-tolerated, certain situations require immediate medical intervention.

> Warning: Stop taking Icatibant and call your doctor or 911 immediately if you experience any of the following:

1. 1Laryngeal Attack Progression: If you inject Icatibant for a throat attack and your breathing does not improve, or if the swelling gets worse, seek emergency care immediately. Icatibant may not work fast enough to prevent total airway closure in some severe cases.
2. 2Anaphylaxis or Severe Allergic Reaction: Symptoms include hives, swelling of the tongue or face (different from your usual HAE swelling), rapid heart rate, difficulty breathing, or feeling like you might pass out. While rare, any peptide-based drug carries a small risk of triggering an immune response.
3. 3Severe Dizziness or Syncope (Fainting): If you feel extremely faint or lose consciousness after an injection.

Because Icatibant is used intermittently for acute attacks, there is little evidence of long-term, cumulative side effects. Clinical studies following patients who used Icatibant over several years found no evidence of 'tachyphylaxis' (where the drug becomes less effective over time) and no significant increase in the frequency or severity of side effects with repeated use.

One area of clinical interest is the development of anti-drug antibodies. Because Icatibant is a synthetic peptide, the body could theoretically recognize it as 'foreign' and create antibodies against it. However, clinical trials showed that the development of these antibodies is rare and, when they do occur, they do not appear to neutralize the drug's effect or increase the risk of allergic reactions.

No FDA black box warnings for Icatibant. The FDA has determined that the safety profile of Icatibant does not warrant its most severe warning level, provided it is used as directed for the treatment of HAE.

Report any unusual symptoms or persistent reactions to your healthcare provider. Monitoring the frequency of your attacks and your response to Icatibant is an essential part of managing Hereditary Angioedema.

Icatibant is a highly specialized medication that must be used with caution. The most critical safety point is that Icatibant is not a substitute for emergency medical care, particularly in the case of laryngeal (throat) attacks. While Icatibant can effectively stop the progression of swelling, laryngeal edema can be fatal within minutes. Patients must always seek emergency department evaluation immediately after self-treating a laryngeal attack to ensure their airway remains stable.

No FDA black box warnings for Icatibant. Unlike some other HAE treatments (such as certain blood-derived products that may carry risks of thromboembolic events), Icatibant does not have a black box warning as of 2026.

Laryngeal Attacks

As noted, laryngeal attacks can result in airway obstruction. Patients should be advised that self-administration of Icatibant for laryngeal attacks is only the first step. Immediate medical attention is required because the swelling may not resolve quickly enough, or a second 'rebound' wave of swelling could occur.

Injection Site Reactions

Patients should be prepared for significant local skin reactions. Nearly all patients will experience redness, swelling, and burning. These reactions can be mistaken for an allergic reaction (hives). If the reaction is limited to the site of injection and does not include systemic symptoms like wheezing or throat tightening, it is likely a standard side effect of the drug.

Cardiovascular Risks

There is a theoretical concern regarding the use of Icatibant in patients with ischemic heart disease (such as a history of heart attack or stable angina). Bradykinin is known to have a protective effect on the heart during periods of low blood flow (ischemia). By blocking the B2 receptor, Icatibant could theoretically worsen heart muscle damage during an active cardiac event. While no major adverse cardiac events were seen in clinical trials, patients with known coronary artery disease should use Icatibant with caution and only under close medical supervision.

Hypersensitivity

As with any peptide medication, there is a risk of hypersensitivity reactions. Patients with a known allergy to icatibant acetate or any of the inactive ingredients (sodium chloride, acetic acid, sodium hydroxide) must not use this medication.

There are no specific laboratory monitoring requirements (like regular blood draws) for patients using Icatibant intermittently. However, healthcare providers typically monitor:

• Attack Frequency: To determine if the patient needs to start or adjust preventative (prophylactic) therapy.
• Liver Function: If a patient is using Icatibant very frequently, occasional liver enzyme tests may be performed due to the rare reports of transaminase elevations.
• Injection Technique: Periodic review of the patient's self-injection technique to ensure efficacy and safety.

Icatibant may cause dizziness, drowsiness, or fatigue in some patients. These symptoms can also be a part of the HAE attack itself (especially abdominal attacks). Patients should not drive, ride a bicycle, or operate heavy machinery until they are certain they are not experiencing any neurological side effects from the medication or the attack.

There are no known direct chemical interactions between Icatibant and alcohol. However, alcohol can cause vasodilation (widening of blood vessels), which might theoretically worsen the swelling of an HAE attack. Furthermore, the combination of alcohol and the potential dizziness caused by Icatibant could increase the risk of falls or accidents. It is generally advised to avoid alcohol during an acute HAE attack.

Icatibant is an 'as-needed' medication. There is no risk of withdrawal symptoms or a 'rebound' effect from stopping the use of Icatibant. However, if a patient stops using Icatibant and has no other treatment plan in place, their HAE attacks will remain untreated and potentially life-threatening.

> Important: Discuss all your medical conditions, especially any heart problems, with your healthcare provider before starting Icatibant.

There are no medications that are strictly 'contraindicated' (forbidden) for use with Icatibant based on metabolic pathways. However, from a clinical management standpoint, certain drugs should be avoided in HAE patients regardless of Icatibant use.

ACE Inhibitors (Angiotensin-Converting Enzyme Inhibitors)

Mechanism: ACE inhibitors (such as lisinopril, enalapril, and ramipril) are used to treat high blood pressure and heart failure. The ACE enzyme is also responsible for breaking down bradykinin in the body. When a patient takes an ACE inhibitor, their natural bradykinin levels increase.

Clinical Consequence: Taking an ACE inhibitor can significantly increase the frequency and severity of HAE attacks. While Icatibant blocks the B2 receptor, the sheer volume of bradykinin produced while on an ACE inhibitor may 'overwhelm' the medication or lead to more frequent attacks that require more Icatibant.

Management: Patients with HAE should generally never be prescribed ACE inhibitors. Alternative blood pressure medications, such as ARBs (Angiotensin II Receptor Blockers), are usually preferred, although even ARBs should be used with caution.

Antihypertensive Agents

Because Icatibant can occasionally cause dizziness or low blood pressure (hypotension), using it alongside other blood pressure-lowering medications may have an additive effect. Patients should be monitored for excessive lightheadedness if they are on potent diuretics or beta-blockers.

There are no known interactions between Icatibant and specific foods. Since the drug is administered via subcutaneous injection, its absorption into the bloodstream bypasses the digestive tract entirely. Unlike many oral medications, Icatibant's efficacy is not affected by high-fat meals, dairy, or fiber.

There is limited data on interactions between Icatibant and herbal supplements. However, patients should exercise caution with supplements that are known to have 'vasodilatory' properties (substances that widen blood vessels) or those that affect blood pressure, as these could theoretically interfere with the management of an HAE attack. Examples include:

• Ginkgo Biloba: May affect blood flow and vessel permeability.
• Garlic Supplements: In high doses, may have mild blood pressure-lowering effects.
• St. John’s Wort: While it primarily interacts with the CYP450 system (which Icatibant avoids), it can affect overall drug metabolism and should be discussed with a doctor.

Icatibant is not known to interfere with common laboratory tests, such as glucose monitoring, cholesterol tests, or standard urine screens. However, as mentioned previously, it may cause a transient (temporary) increase in liver transaminases (ALT/AST). If you are having blood work done shortly after treating an HAE attack, inform the lab or your doctor that you have recently used Icatibant so they can correctly interpret any slight elevations in liver enzymes.

Mechanism of Interaction Summary

Icatibant’s primary interaction profile is pharmacodynamic rather than pharmacokinetic. This means the interactions occur because of what the drugs do to the body (e.g., both affecting bradykinin levels) rather than how the body breaks them down. Because Icatibant is not processed by the liver's CYP450 enzymes, it avoids the vast majority of common drug-drug interactions seen with oral medications like statins, antidepressants, or antibiotics.

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking. Even 'natural' products can influence how your body responds to an HAE attack or its treatment.

An absolute contraindication is a condition or factor that serves as a reason to withhold a certain medical treatment due to the harm that it would cause the patient. For Icatibant, there is only one primary absolute contraindication:

Hypersensitivity to Icatibant Acetate

• The Condition: A known, documented allergy to Icatibant or any of its components.
• Why it is Contraindicated: Icatibant is a peptide. In rare cases, the immune system can develop an acute allergic response to the drug itself. Administering Icatibant to a patient with a known allergy could trigger anaphylaxis, a life-threatening systemic allergic reaction that includes airway constriction and a dangerous drop in blood pressure. This would be catastrophic for a patient already experiencing an HAE attack.

Relative contraindications are conditions where the use of the drug may be acceptable if the benefits outweigh the risks, but where extra caution is required.

Ischemic Heart Disease

• The Condition: Patients with a history of myocardial infarction (heart attack), unstable angina, or significant coronary artery disease.
• Why it is a Concern: Bradykinin plays a role in 'ischemic preconditioning'—a process where the heart protects itself during low oxygen states. By blocking the B2 receptor, Icatibant could theoretically interfere with this protective mechanism. In the setting of an acute heart attack, Icatibant could potentially increase the size of the heart muscle injury. Doctors must carefully weigh the risk of the HAE attack against the patient's cardiac status.

Acute Stroke

Similar to the heart, bradykinin may have some protective roles in the brain during an acute ischemic stroke. While evidence is limited, caution is advised when treating HAE attacks in patients who have recently suffered a stroke.

There are no closely related drugs in the same class (bradykinin B2 antagonists) that are currently in wide clinical use, so the risk of cross-sensitivity with other medications is considered very low. However, patients should always inform their doctor if they have had reactions to other synthetic peptide drugs, such as certain types of insulin or peptide hormones.

> Important: Your healthcare provider will evaluate your complete medical history, including your heart health and any previous allergic reactions, before prescribing Icatibant. Always keep an updated list of your allergies and share it with any medical professional treating you for an HAE attack.

Icatibant is classified as a medication that should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

• Risk Summary: There are no adequate and well-controlled studies of Icatibant in pregnant women. In animal studies (rats and rabbits), Icatibant was found to cause delayed parturition (delayed birth) and increased fetal loss when administered at doses much higher than the human dose. These effects are likely due to the role bradykinin plays in the onset of labor.
• Clinical Considerations: An untreated HAE attack in a pregnant woman can be life-threatening for both the mother and the fetus. If an attack occurs, the healthcare provider must decide if Icatibant is the safest option or if other treatments (like C1-inhibitor concentrates, which are generally preferred in pregnancy) should be used.

It is not known whether Icatibant is excreted in human breast milk. However, animal studies in lactating rats have shown that Icatibant is present in the milk of treated animals.

• Risk-Benefit: Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or to withhold the drug, taking into account the importance of the drug to the mother. If Icatibant is used, some experts suggest 'pumping and discarding' milk for 12-24 hours after a dose to minimize infant exposure.

As of 2026, the FDA has not approved Icatibant for use in patients under the age of 18.

• Safety Gap: While clinical trials (such as the E-FAST study) have looked at the use of Icatibant in children as young as 2 years old, the data has not yet led to a change in the US labeling.
• Concerns: There are theoretical concerns about how blocking bradykinin might affect growth and development in children, although no such effects were seen in short-term pediatric trials in Europe.

Clinical studies of Icatibant included a sufficient number of patients aged 65 and over to determine that they respond similarly to younger patients.

• Pharmacokinetics: Elderly patients may have a slightly higher peak concentration and a longer half-life (about 2.5 hours vs 2 hours). This is likely due to age-related declines in kidney function.
• Considerations: No dose adjustment is required, but because older adults are more likely to have underlying heart disease (ischemic heart disease), the precautions regarding cardiac safety are especially relevant for this group.

Icatibant has been studied in patients with varying degrees of kidney function.

• Adjustment: No dosage adjustment is needed for patients with mild, moderate, or severe renal impairment.
• Dialysis: It is unknown if Icatibant is cleared by hemodialysis, but given its rapid metabolism by proteolytic enzymes in the blood and tissues, dialysis is unlikely to be necessary for drug clearance.

Because Icatibant is not metabolized by the liver's primary enzyme systems (CYP450), liver disease does not significantly change how the drug is processed.

• Adjustment: No dosage adjustment is required for patients with hepatic impairment (Child-Pugh scores A, B, or C).

> Important: Special populations require individualized medical assessment. If you are pregnant, planning to become pregnant, or have chronic kidney or liver issues, ensure your HAE specialist is aware so they can tailor your emergency treatment plan.

Icatibant is a synthetic decapeptide with the sequence: D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-D-Tic-Oic-Arg. It is a potent and selective competitive antagonist at the bradykinin B2 receptor.

In Hereditary Angioedema (HAE), the absence of functional C1-esterase inhibitor leads to the over-activation of plasma kallikrein, which cleaves high-molecular-weight kininogen to release excessive amounts of bradykinin. Bradykinin is the primary mediator of HAE symptoms. It binds to B2 receptors on vascular endothelial cells, triggering the release of nitric oxide and prostacyclin, and causing the contraction of the endothelial cytoskeleton. This creates gaps between the cells, allowing plasma to leak into the interstitial space (edema).

Icatibant has an affinity for the B2 receptor that is similar to bradykinin itself (Ki = 0.79 nM). By occupying the receptor without activating it, Icatibant prevents bradykinin from initiating the signaling cascade that leads to swelling. It does not inhibit the production of bradykinin, but rather blocks its 'docking station.'

• Onset of Action: Patients typically begin to feel symptom relief within 30 to 120 minutes after injection. The median time to 'onset of symptom relief' in clinical trials was 2.0 hours.
• Duration: The blockade of the B2 receptor is effective for several hours, which is usually enough time for the underlying 'bradykinin storm' of an HAE attack to subside.
• Specificity: Icatibant is highly selective for the B2 receptor. It has no significant activity at the B1 receptor, nor does it affect other receptor systems like histamine or serotonin receptors.

| Parameter | Value |

|---|---|

| Bioavailability | 97% (Subcutaneous) |

| Protein Binding | 44% - 50% |

| Half-life | 1.4 - 2.0 hours |

| Tmax | 0.75 hours (45 minutes) |

| Metabolism | Proteolytic cleavage (Non-CYP) |

| Excretion | Renal (90% as metabolites) |

• Molecular Formula: C59H89N19O13S
• Molecular Weight: 1308.5 g/mol (as free base)
• Solubility: Highly soluble in water and physiological saline.
• Structure: It is a peptidomimetic, meaning it mimics the structure of a peptide but contains non-natural amino acids (like D-Tic and Oic) to prevent rapid degradation by common enzymes, giving it a longer duration of action than natural bradykinin.

Icatibant is the first-in-class bradykinin B2 receptor antagonist. It is distinct from other HAE treatments such as C1-esterase inhibitor replacements (e.g., Berinert, Cinryze), kallikrein inhibitors (e.g., Kalbitor, Takhzyro), or attenuated androgens.