A complement (C5) inhibitor biologic
Eculizumab
A biologic for rare conditions that blocks part of the immune system, with a key requirement for meningococcal vaccination first.
What is Eculizumab?
Eculizumab is a biologic medicine used for some rare conditions, including paroxysmal nocturnal haemoglobinuria (PNH), atypical haemolytic uraemic syndrome (aHUS) and certain others. It blocks a protein called C5 in the complement system, part of the immune defences, which stops it from damaging the body's own cells. The most important safety point is that it greatly increases the risk of life-threatening meningococcal infection, so meningococcal vaccination is required before starting, often with standby antibiotics and a patient alert card. It is given as a drip into a vein.
Education and reference only. This is a plain-language guide to Eculizumab — 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
Eculizumab is a biologic medicine, a laboratory-made antibody, used to treat several rare conditions in which part of the immune system called the complement system harms the body's own cells. These include paroxysmal nocturnal haemoglobinuria (PNH), where red blood cells are destroyed, atypical haemolytic uraemic syndrome (aHUS), which affects the kidneys and blood, and some other rare conditions affecting nerves or muscles. It is given as a drip into a vein at regular intervals under specialist care.
How it works
Eculizumab blocks a complement protein called C5, stopping the final, most damaging part of the complement cascade from forming. In conditions like PNH, this cascade attacks and destroys red blood cells; in aHUS it damages small blood vessels and the kidneys. By switching off this part of the immune system, eculizumab protects these cells and tissues. The same action, however, removes an important defence against certain bacteria, which is why protection against meningococcal infection is essential.
Company & origin
Originated / developed by: Alexion.
A biologic medicine used in the UK for some rare conditions, which works by switching off part of the immune system called the complement system.
Practical use
How to take Eculizumab
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is given as a drip into a vein at regular intervals, arranged and supervised by a specialist team.
- Make sure you have had the required meningococcal vaccination before starting, and any boosters your team advises.
- Carry your patient alert card at all times and show it to any healthcare professional you see.
- Keep any standby antibiotics you are given to hand, and use them exactly as instructed if advised.
- Seek urgent medical help for fever, severe headache, neck stiffness, a rash or sensitivity to light, as these can signal serious infection.
Weighing it up
Advantages & disadvantages of Eculizumab
Advantages
- Can be life-changing in rare conditions such as PNH and aHUS by protecting blood cells and the kidneys.
- Reduces the destruction of red blood cells and the need for blood transfusions in PNH.
- Targets a specific part of the immune system rather than suppressing it broadly.
Disadvantages
- Greatly increases the risk of life-threatening meningococcal infection, needing vaccination and vigilance.
- Must be given as a regular hospital drip, which is demanding over the long term.
- Requires careful specialist supervision and an alert card carried at all times.
Practical use
Good to know
The single most important thing to understand about eculizumab is its infection risk. By blocking the complement system, it sharply increases the risk of life-threatening meningococcal infection (a cause of meningitis and blood poisoning). For this reason, meningococcal vaccination is required before starting, treatment is usually delayed until you are protected, and you are often given standby antibiotics and a patient alert card to carry at all times. You must seek urgent medical care for symptoms such as fever, severe headache, neck stiffness, a rash, sensitivity to light or feeling very unwell, even if vaccinated, because vaccination does not remove the risk completely. Always show your alert card to any healthcare professional. It is given as a regular hospital drip and started only by specialist teams.
Who should not take it / use with caution
- It must not be started in someone with an unresolved serious meningococcal infection.
- It should not be started in people who are not protected against meningococcal infection unless urgent treatment justifies starting with antibiotic cover.
- It is used with caution in people with other active infections, which should be assessed first.
Monitoring
- Confirming meningococcal vaccination and protection before and during treatment.
- Watching closely for any signs of infection, especially meningococcal symptoms.
- Reviewing blood results and disease control to judge how well it is working.
Side effects
- Headache, especially when starting, along with cold-like symptoms and nausea.
- Increased risk of infections, most importantly serious meningococcal infection.
- Infusion reactions; tiredness and back or joint aches in some people.
Key interactions
- It works alongside vaccination, so meningococcal and other recommended vaccines are an essential part of treatment.
- Tell your team about all your medicines, including any other immune-affecting treatments.
- Live vaccines should be discussed with your specialist before they are given.
Available as: Infusion into a vein, given at regular intervals under specialist care.
Answers
Eculizumab: frequently asked questions
Why do I need a meningococcal vaccine before eculizumab?
Eculizumab sharply raises the risk of life-threatening meningococcal infection, so vaccination is required before starting, often with standby antibiotics and a patient alert card.
Does the vaccine fully protect me?
No. Vaccination lowers but does not remove the risk, so you must still seek urgent care for fever, severe headache, neck stiffness, a rash or sensitivity to light.
What is the patient alert card for?
It tells any healthcare professional that you are on eculizumab and at higher risk of serious infection, so carry it at all times and show it whenever you seek care.
What conditions is it used for?
It is used for rare conditions such as paroxysmal nocturnal haemoglobinuria (PNH), atypical haemolytic uraemic syndrome (aHUS) and some others, under specialist care.
How is it given?
It is given as a drip into a vein at regular intervals, arranged and supervised by a specialist team.
Authoritative sources
- BNF
- NICE CKS
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