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C1-Esterase Inhibitor (Recombinant)

Brand name: Ruconest
Drug class: Complement Inhibitors
CAS number: CAS-80295-38-1

Medically reviewed by on Jan 31, 2022. Written by ASHP.


Biosynthetic (recombinant DNA-origin) preparation of complement 1 (C1)-esterase inhibitor.

C1-esterase inhibitor is a naturally occurring inhibitor of certain serine proteases (e.g., C1 complement, kallikrein, coagulation factor XIIa, plasmin) involved in the complement, coagulation (contact), and fibrinolytic systems.

Uses for C1-Esterase Inhibitor (Recombinant)

Hereditary Angioedema

Treatment of acute angioedema attacks in patients with hereditary angioedema (HAE). Designated an orphan drug by FDA for this use.

Clinical studies were conducted principally in patients with abdominal, facial, or peripheral angioedema; efficacy in patients with laryngeal HAE attacks not established.

Recommended by US and international consensus guidelines as one of several options for treatment of acute HAE attacks; other drugs include ecallantide (plasma kallikrein inhibitor) and icatibant (bradykinin B2-receptor antagonist).

C1-Esterase Inhibitor (Recombinant) Dosage and Administration


IV Administration

Administer by slow IV injection.

Initiate therapy under supervision of a qualified healthcare professional experienced in the treatment of HAE. May be self-administered after appropriate training is provided.

Do not mix or administer with any other drug or solution.

Vials are for single use only; discard any unused portions.


Allow vials of drug and diluent (sterile water for injection) to reach room temperature prior to reconstitution.

Reconstitute vial containing 2100 units of C1-esterase inhibitor (recombinant) with 14 mL of sterile water for injection. Add diluent slowly to avoid forceful impact on the powder. Gently swirl vial to ensure complete dissolution. Resultant solution contains 150 units/mL. If more than 1 vial is required to obtain a dose, may pool reconstituted contents of multiple vials into a single administration device (i.e., syringe).

Administer reconstituted solutions immediately or within 8 hours if stored at 2–8°C.

Rate of Administration

Administer by IV injection over approximately 5 minutes.


Dosage of C1-esterase inhibitor (recombinant) is expressed in international units (IU, units). One unit of C1-esterase inhibitor (recombinant) is equivalent to the C1-esterase-inhibiting activity present in 1 mL of pooled normal plasma.

Pediatric Patients

Hereditary Angioedema
Treatment of Acute Angioedema Attacks

Adolescents 13–17 years of age: 50 units/kg (up to 4200 units) for patients weighing <84 kg; 4200 units in patients weighing ≥84 kg.

May administer a second dose if attack symptoms persist.


Hereditary Angioedema
Treatment of Acute Angioedema Attacks

50 units/kg (up to 4200 units) for patients weighing <84 kg; 4200 units in patients weighing ≥84 kg.

May administer a second dose if attack symptoms persist.

Prescribing Limits

Pediatric Patients

Hereditary Angioedema
Treatment of Acute Angioedema Attacks

Adolescents 13–17 years of age: Maximum 4200 units per dose; do not exceed 2 doses within a 24-hour period.


Hereditary Angioedema
Treatment of Acute Angioedema Attacks

Maximum 4200 units per dose; do not exceed 2 doses within a 24-hour period.

Cautions for C1-Esterase Inhibitor (Recombinant)


  • Known hypersensitivity to rabbits or rabbit-derived products.

  • Known life-threatening immediate hypersensitivity, including anaphylaxis, to C1-esterase inhibitor preparations.


Thrombotic Events

Risk of thromboembolic events. Reported with plasma-derived C1-esterase inhibitor at recommended doses in patients with underlying risk factors (e.g., presence of indwelling venous catheter/access device, history of thrombosis, underlying atherosclerosis, use of oral contraceptives or certain androgens, morbid obesity, immobility).

Clinical studies to date have not suggested an increased thrombotic risk with C1-esterase inhibitor (recombinant).

Closely monitor patients with known risk factors for thromboembolism.


Potential for immunogenicity with use of all therapeutic proteins, including C1-esterase inhibitor (recombinant). Development of non-neutralizing antibodies to C1-esterase inhibitor (recombinant) reported in clinical trials; however, clinically important effects not observed.

Sensitivity Reactions


Risk of severe hypersensitivity reactions (e.g., urticaria, chest tightness, wheezing, hypotension, anaphylaxis). (See Contraindications under Cautions.) Anaphylaxis was reported in an individual with preexisting allergy to rabbit protein.

If hypersensitivity occurs, discontinue drug immediately and initiate appropriate treatment. Because symptoms of hypersensitivity can resemble acute attacks of HAE, carefully consider treatment method.

Specific Populations


Category B.

No adequate and well-controlled studies in pregnant women. Animal studies suggest a possibility of adverse embryofetal effects.


Not known whether C1-esterase inhibitor (recombinant) is distributed into human milk. Use with caution.

Pediatric Use

Safety and efficacy not established in pediatric patients <13 years of age; use of the drug in adolescents 13–17 years of age is supported by data from approval studies.

Geriatric Use

Insufficient experience in patients >65 years of age to determine whether geriatric patients respond differently than younger patients.

Hepatic Impairment

Pharmacokinetics not evaluated in patients with hepatic impairment.

Renal Impairment

Pharmacokinetics not evaluated in patients with renal impairment.

Common Adverse Effects

Headache, nausea, diarrhea.

Interactions for C1-Esterase Inhibitor (Recombinant)

No formal drug interaction studies to date.

C1-Esterase Inhibitor (Recombinant) Pharmacokinetics


Plasma Concentrations

Peak plasma concentrations attained in approximately 0.3 hours following a single 50-unit/kg dose in asymptomatic patients.



Not known whether distributed into human milk.



Approximately 2.5 hours following a 50-unit/kg dose in asymptomatic patients.

Exhibits nonlinear clearance.

Elimination half-life has been reported to be shorter than that of plasma-derived C1-esterase inhibitor due to differences in glycosylation.




Powder for Injection

2–25°C; do not freeze. Store in original container and protect from light.

May store reconstituted solutions at 2–8°C for up to 8 hours; do not freeze.


  • Serine protease inhibitor that principally regulates the activation of the complement and intrinsic coagulation (e.g., contact system) pathways. Also plays a role in the fibrinolytic system.

  • Regulates contact system activation by inhibiting plasma kallikrein and coagulation factor XIIa; such actions prevent formation of bradykinin, the presumed mediator of increased vascular permeability in HAE.

  • Blocks both the spontaneous activation of C1 complement and formation of activated C1 complement, suppressing the classical complement pathway.

  • Also exhibits inhibitory effects on plasmin.

  • Binds to and forms irreversible complexes with target protease, which are then inactivated and removed from circulation.

  • Biosynthetic (recombinant DNA origin) preparation of human C1-esterase inhibitor produced from the milk of transgenic (genetically modified) rabbits. Undergoes a series of viral reduction steps (e.g., pasteurization, precipitation, nanofiltration, chromatography) to reduce risk of viral transmission.

  • Structurally and functionally similar to plasma-derived C1-esterase inhibitor.

Advice to Patients

  • Importance of discussing potential risks and benefits of therapy with the patient prior to prescribing or administering the drug.

  • Importance of instructing patients to read the manufacturer's product information and instructions for use.

  • Importance of patients immediately informing a clinician if any signs or symptoms of hypersensitivity (e.g., urticaria, chest tightness, wheezing, hypotension, anaphylaxis) occur during or after administration of C1-esterase inhibitor (recombinant).

  • Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.

  • Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses.

  • Importance of informing patients of other important precautionary information. (See Cautions.)


Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

C1-Esterase Inhibitor (Recombinant)


Dosage Forms


Brand Names



For injection, for IV use

2100 units



AHFS DI Essentials™. © Copyright 2022, Selected Revisions January 31, 2022. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, Maryland 20814.

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