Mepolizumab
Also known as: Nucala
Mepolizumab is a targeted injection that lowers eosinophils, the white cells that drive certain forms of vasculitis and severe asthma. In my clinic its main value is in EGPA, where it helps keep the disease quiet and lets me reduce steroids.
Calm, careful medication review by a consultant rheumatologist.
What this medicine is
Mepolizumab is a monoclonal antibody that blocks interleukin-5, the signal that eosinophils depend on to grow and survive. Lowering eosinophils reduces the inflammation they cause in the airways, sinuses, nerves and other tissues. It is given as a subcutaneous injection, meaning a small injection under the skin, on a regular schedule rather than daily, and it can be given in clinic or taught for use at home. It is added to your existing treatment rather than replacing it. Doses differ between conditions, so your specialist sets the regimen and I do not publish dose schedules here.
Uses and context
The rheumatology use I care about most is eosinophilic granulomatosis with polyangiitis, previously called Churg-Strauss syndrome. This is a vasculitis with asthma, nasal and sinus disease, a high eosinophil count and sometimes nerve, skin, gut or heart involvement. Mepolizumab is approved for relapsing or refractory EGPA and helps achieve remission while reducing the dose of steroids needed. It is also widely used in severe eosinophilic asthma, chronic rhinosinusitis with nasal polyps and hypereosinophilic syndrome, so you may be sharing care with a respiratory physician or ENT surgeon. It does not treat rheumatoid arthritis, lupus or other non-eosinophilic rheumatic diseases.
How this relates to rheumatology care
How I use it in practice: in EGPA, mepolizumab is a maintenance and steroid-sparing medicine rather than a rescue treatment. If you have organ-threatening or life-threatening disease, that is treated first with steroids and a stronger immunosuppressant such as rituximab or cyclophosphamide. Once things are stable, mepolizumab helps hold remission and lets me taper prednisolone, which is where most of the long-term harm in EGPA actually comes from. Benefit usually shows over one to three months as asthma control improves, eosinophils fall and flares become less frequent. I do not stop your inhalers or reduce steroids quickly just because you feel better, and any steroid taper is planned and gradual. Related pages you may find useful are my guides to EGPA and vasculitis.
What safety checks may matter
Confirming the diagnosis and eosinophil count before starting, since this medicine only helps eosinophil-driven disease
Screening and treating any parasitic worm infection before starting, as eosinophils help fight these
A review of your asthma, sinus and nerve symptoms so we have a clear baseline to judge response against
A written steroid tapering plan, with review of bone protection and blood sugar while you are still on prednisolone
Blood count and inflammatory markers monitored at review, including the eosinophil count
Vaccinations reviewed, with non-live vaccines such as influenza, COVID-19 and pneumococcal encouraged
A plan for what to do if asthma or vasculitis symptoms return, rather than waiting for your next appointment
Side effects and red flags
If you have emergency symptoms such as severe allergic reaction, breathing difficulty, chest pain, stroke-like symptoms, severe abdominal pain, vomiting blood, black stools, sudden vision loss, severe infection symptoms, or severe weakness or confusion, please seek urgent medical care first rather than waiting for a WhatsApp reply.
Worsening breathlessness, wheeze or needing your reliever inhaler much more often
New numbness, tingling, burning pain or weakness in the hands or feet, which can mean nerve involvement
Chest pain, palpitations, ankle swelling or breathlessness lying flat, which can suggest heart involvement in EGPA
A new purple or red rash, especially on the legs, or painful skin nodules
Fever, night sweats or unexplained weight loss
Facial or tongue swelling, widespread rash or difficulty breathing after an injection, which may be a severe allergic reaction
Things worth knowing day to day
Injection-site reactions such as redness, itching or a small lump are the most common side effect and usually settle within a day or two.
Headache is fairly common in the first weeks and generally improves.
Do not stop your inhalers or oral steroids on your own. Sudden steroid withdrawal in EGPA can trigger a serious relapse.
Shingles has been reported in people on mepolizumab. Tell me early about a painful blistering rash in a band, and ask about the inactivated shingles vaccine.
If you travel to areas where worm infections are common, or you develop diarrhoea and abdominal pain after travel, tell me so this can be checked.
Store the pen or syringe in the fridge as instructed, and let it come to room temperature before injecting for more comfort.
Pregnancy and breastfeeding should be discussed with me before you plan a pregnancy, so we can weigh keeping your disease controlled against limited pregnancy data.
Keep your respiratory or ENT specialist in the loop, since much of the day-to-day benefit shows in your breathing and sinuses.
Questions patients often ask me about this medicine
Speak with me
If you have EGPA and are struggling to come off steroids, or mepolizumab has been suggested and you want it explained properly, please message my clinic. I will review your eosinophil counts, your asthma control and your steroid dose together.
Trusted patient information sources
Other medications used in rheumatology care
This page is for general education only and does not replace medical advice. Please consult a qualified healthcare professional for diagnosis and treatment. Do not start, stop, or change any medicine without advice from your doctor.