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How long does it take for Nucala to work?

Medically reviewed by Carmen Fookes, BPharm. Last updated on Sep 28, 2020.

Official Answer


Nucala starts working within 48 hours; however, it may take up to 4 weeks before the maximum effect of Nucala is seen for both asthma and eosinophilic granulomatosis with polyangiitis (EGPA). In asthma, the greatest reductions in eosinophils were seen with higher dosages, for example, a 64% reduction in eosinophils was seen with a 12.5mg SC dose and a 90% reduction was seen with a 250mg SC dose after 48 hours.

Nucala (mepolizumab) is a biologic that is administered by subcutaneous injection once every four weeks.

It is approved as an add-on maintenance treatment for severe eosinophilic asthma in adults and children aged 6 and older. It is also approved for the treatment of adult patients with eosinophilic granulomatosis with polyangiitis (Churg-Strauss syndrome) and for the treatment of patients ≥12 years with hypereosinophilic syndrome (HES).

In trials of people with eosinophilic asthma:

  • Reductions in blood eosinophils were seen within 48 hours of a dose of mepolizumab for all treatment doses
  • Greater eosinophil reductions were seen with higher mepolizumab dosages, for example, 64% with a 12.5mg SC dose, 78% for a 75mg dose, and 90% with a 250mg SC dose
  • After treatment with Nucala 100mg SC every 4 weeks, blood eosinophils showed an average reduction of 84% (down to 40 cells/mcL) in adults
  • After treatment with Nucala 40mg SC every 4 weeks, blood eosinophils showed an average reduction of and 85% (down to 48 cells/mcL) in children aged 6 to 11 years.
  • The greatest effect was seen after 4 weeks of treatment and this was maintained throughout the treatment period.

In trials of people with EGPA blood eosinophil levels were reduced by 83% (down to 38 cells/mcL) with mepolizumab 300mg every 4 weeks.


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