C1-inhibitor (plasma-derived or recombinant protein) for hereditary angioedema
C1-esterase inhibitor
A blood-derived protein given by injection to treat and help prevent attacks of hereditary angioedema, a condition causing sudden severe swelling.
What is C1-esterase inhibitor?
C1-esterase inhibitor is a specialist medicine used to treat, and in some cases prevent, attacks of hereditary angioedema, a rare condition that causes sudden, severe swelling of the skin, the gut or the airway. It replaces C1-inhibitor, a protein that people with the condition are missing or low in, helping the swelling settle or attacks happen less often. It is given by injection into a vein and is usually well tolerated, with a small risk of blood clots. Because most forms are made from human blood plasma, there are the usual very small risks linked to plasma-derived products. Any attack involving the throat or airway is an emergency needing urgent help.
Education and reference only. This is a plain-language guide to C1-esterase inhibitor — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
C1-esterase inhibitor is a replacement form of a natural protein called C1-inhibitor, which people with hereditary angioedema are missing or short of. Hereditary angioedema is an inherited condition in which a lack of this protein leads to episodes of severe swelling affecting the skin, the gut (causing pain) or, most dangerously, the airway. The medicine is given by injection into a vein and can be used both to treat an attack as it happens and, with some products, to help prevent attacks in people who have them often. Most versions are purified from human blood plasma, while a recombinant (laboratory-made) version also exists. It is prescribed and supervised by a specialist service.
How it works
People with hereditary angioedema lack enough C1-inhibitor, a protein that normally keeps in check the processes that produce bradykinin, the chemical that makes blood vessels leak and causes swelling. C1-esterase inhibitor tops up this missing protein, restoring control and helping an attack settle or reducing how often attacks happen. Because it works only while it is in the body, it is given as an injection when an attack starts or, for prevention, on a regular schedule. It is given into a vein, often by a healthcare professional or by the person after suitable training.
Company & origin
Originated / developed by: Specialist manufacturers.
A specialist protein medicine used in the UK to treat and prevent attacks of hereditary angioedema, replacing a missing or low protein in the blood.
Practical use
How to take C1-esterase inhibitor
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Use it as your specialist team has arranged, given as an injection into a vein either to treat an attack or, for prevention, on a regular schedule.
- If it is for treating attacks, use it as early in an attack as possible, as earlier treatment usually works better.
- If it is for prevention, use it on the regular schedule set for you rather than waiting for symptoms.
- Keep a clear plan for treating any attack that breaks through, especially if you are using it to prevent attacks.
- Seek emergency help straight away if an attack involves your throat, mouth or breathing, even after using it.
Weighing it up
Advantages & disadvantages of C1-esterase inhibitor
Advantages
- Directly replaces the missing C1-inhibitor protein, treating attacks and, with some products, helping prevent them.
- Can treat attacks affecting the skin, gut or airway and is generally well tolerated.
- Can often be given by the person at home after appropriate training.
Disadvantages
- Given by injection into a vein, which takes training and access to a vein.
- Most forms are made from human blood plasma, carrying the usual very small risks of plasma-derived products.
- Carries a small risk of blood clots, and airway attacks still need emergency help.
Practical use
Good to know
An important thing to understand is that the same protein can be used in two ways: to treat an attack that is happening and, with certain products, to prevent attacks in people who have them frequently, so it is worth being clear which role yours is for. Because most forms are made from human blood plasma, there are the usual very small theoretical risks attached to plasma-derived products, even though donated plasma is carefully screened and treated; the recombinant version avoids these. A recognised, though uncommon, risk is of blood clots, particularly with higher use or in people already prone to clotting, so tell your team about any clotting history. It is generally well tolerated. As with all hereditary angioedema, any attack involving the throat or airway is a medical emergency: treat it and seek emergency help at the same time. The specialist team will train you, set out when and how to use it, and review how well it is working.
Who should not take it / use with caution
- People who have had a serious allergic reaction to a C1-esterase inhibitor product should not use that product.
- It is used with extra care in people with a history of blood clots, because of a small clotting risk.
- It should only be used under a specialist hereditary angioedema service that provides training and a treatment plan.
Monitoring
- Reviewing how well attacks respond, or how often they happen if it is used for prevention.
- Watching for signs of blood clots and for any allergic-type reactions.
- Checking the person is confident with the injection technique where they self-administer.
Side effects
- Reactions where the injection is given, or headache and nausea in some people.
- Uncommonly, blood clots, especially with higher use or in people prone to clotting.
- Rarely, allergic-type reactions; airway involvement during an attack always needs emergency care.
Key interactions
- There are few well-established routine medicine interactions, but tell your team about all your medicines.
- Tell your team about any history of blood clots or medicines affecting clotting, because of the small clot risk.
- It is used alongside, not instead of, emergency care when the airway is involved.
Available as: A powder made up into a solution for injection into a vein.
Answers
C1-esterase inhibitor: frequently asked questions
What is C1-esterase inhibitor used for?
It is used to treat attacks of hereditary angioedema and, with some products, to help prevent them, by replacing the C1-inhibitor protein that people with the condition are missing or low in.
Is it made from blood?
Most forms are purified from human blood plasma, which is carefully screened and treated, so there are only very small theoretical risks; a recombinant laboratory-made version also exists.
How is it given?
It is given as an injection into a vein, either to treat an attack or, for prevention, on a regular schedule, and can often be done at home after training.
Does it have any serious risks?
It is generally well tolerated, but there is a small risk of blood clots, so tell your team about any history of clotting before using it.
What if my throat is involved?
Swelling involving the throat or breathing is an emergency; seek urgent help straight away, even after using C1-esterase inhibitor.
Authoritative sources
- BNF
- NICE CKS
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