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Anti-IL-5 Monoclonal Antibody Pregnancy: Use with caution — limited data; potential to affect fetal eosinophil development; use only if benefit outweighs risk

Mepolizumab (CRSwNP)

Brand names: Nucala

Adult dose

Dose: 100 mg SC every 4 weeks
Route: Subcutaneous injection
Frequency: Every 4 weeks
Max: 100 mg per dose
CRSwNP add-on to intranasal corticosteroids in adults with inadequate response to surgery/oral steroids; same dose as asthma indication

Paediatric dose

Dose: Not established for CRSwNP N/A/kg
Route: N/A
Frequency: N/A
Max: N/A
CRSwNP adults only; severe eosinophilic asthma licensed ≥6 years

Dose adjustments

Renal

No dose adjustment required

Hepatic

No dose adjustment required

Paediatric weight-based calculator

CRSwNP adults only; severe eosinophilic asthma licensed ≥6 years

Clinical pearls

  • SYNAPSE trial (Han et al. NEJM 2021): mepolizumab significantly reduced nasal polyp score and need for surgery in CRSwNP (surgery rate 4% vs 23% placebo at 52 weeks) — NICE TA662 approved; particularly effective in patients with high blood eosinophil counts (≥150/μL)
  • Eosinophilic CRSwNP: most severe form of nasal polyposis with high tissue eosinophilia, frequent asthma comorbidity, and aspirin-exacerbated respiratory disease (AERD) — blood eosinophil count is the best predictor of mepolizumab response
  • AERD/Samter's triad (asthma + nasal polyps + aspirin sensitivity): mepolizumab particularly beneficial — anti-IL-5 therapy reduces eosinophil-driven inflammation, the main pathogenic mechanism in AERD; allows reduced oral steroid burden
  • Overlap with severe asthma: many CRSwNP patients also have severe eosinophilic asthma — mepolizumab treats both conditions simultaneously with same 100 mg SC monthly dose; simplifies management in overlap patients
  • Blood eosinophil threshold: NICE TA662 requires blood eosinophils ≥150 cells/μL for CRSwNP indication; patients with higher eosinophil counts (≥300/μL) show greatest benefit in clinical trials

Contraindications

  • Known hypersensitivity
  • Active acute infections (delay dose)

Side effects

  • Headache
  • Back pain
  • Injection site reactions
  • Fatigue
  • Eczema (redistribution of eosinophils)

Interactions

  • Live vaccines — avoid

Monitoring

  • Nasal polyp score
  • SNOT-22
  • Blood eosinophil count (baseline and response)
  • Need for oral steroids/surgery (surrogate endpoint)
  • Asthma control if concurrent

Reference: BNFc; BNF 90; SYNAPSE trial (Han et al. NEJM 2021); NICE TA662; MHRA SPC Nucala; Fokkens et al. EPOS 2020. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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