Pegylated interferon beta (immunomodulator)

Peginterferon beta-1a

Brand names: Plegridy

Adult dose

Dose: 125 micrograms SC every 14 days (titration: 63 micrograms day 1, 94 micrograms day 15, 125 micrograms day 29)

Route: Subcutaneous (or IM)

Frequency: q14d

Clinical pearls

NICE TA624 / TA616: option for relapsing-remitting MS
ABN MS-DMT prescribing guidance — first-line moderate-efficacy DMT
Reduced injection frequency vs other interferons (q14d vs daily/3× weekly)

Contraindications

Severe depression / suicidal ideation
Decompensated hepatic disease
Pregnancy (per latest MHRA review — case-by-case)
Hypersensitivity

Side effects

Flu-like symptoms (mitigate with paracetamol/ibuprofen)
Injection-site reactions
Hepatotoxicity
Depression
Cytopenias
Thrombotic microangiopathy (rare)
Seizures (rare)

Interactions

Hepatotoxic drugs

Monitoring

FBC
LFTs
TFTs
Mental health
Injection-site review

Reference: BNF; NICE TA624; ABN MS-DMT prescribing guideline; SmPC; https://bnf.nice.org.uk/drugs/peginterferon-beta-1a/. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways