Anti-IL-5 Monoclonal Antibody Pregnancy: Avoid unless clearly needed — insufficient data

Mepolizumab

Brand names: Nucala

Adult dose

Dose: 100 mg SC every 4 weeks

Route: Subcutaneous injection (upper arm, thigh, or abdomen)

Frequency: Every 4 weeks

Max: 100 mg per 4 weeks

For severe eosinophilic asthma (blood eosinophils ≥150 cells/mcL at initiation, or ≥300 cells/mcL at any time in past year). Also for EGPA and hypereosinophilic syndrome.

Paediatric dose

Route: SC

Frequency: Every 4 weeks

Max: 40 mg per dose (6–11 years); 100 mg per dose (≥12 years)

Concentration: 100 mg/mL mg/ml

Licensed for severe eosinophilic asthma ≥6 years. Dose by age: 6–11 years: 40 mg SC every 4 weeks.

Dose adjustments

Renal

No dose adjustment required

Hepatic

No dose adjustment required

Clinical pearls

MENSA and DREAM trials: reduces exacerbation rate by ~50% in severe eosinophilic asthma
Blood eosinophil count (BEC) guides eligibility: ≥150 cells/mcL (or ≥300 historical) is threshold
Review at 12 months — continue only if clear response (≥50% reduction in exacerbations)
Can reduce OCS requirement by up to 50% (SIRIUS trial)

Contraindications

Eosinophil count <150 cells/mcL at time of initiation (reassess — may have been higher historically)
Active parasitic infection (treat before starting)

Side effects

Injection site reactions
Headache
Back pain
Fatigue
Hypersensitivity reactions (rare)
Herpes zoster

Interactions

Minimal systemic interactions

Monitoring

Blood eosinophil count
Exacerbation frequency
OCS dose (opportunity for steroid sparing)
Parasitic infection risk

Reference: BNFc; MENSA Trial (Ortega et al, NEJM 2014); SIRIUS Trial (Bel et al, NEJM 2014); BNF; NICE TA339. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Pathways