Pegylated interferon (immunomodulator)

Peginterferon alfa

Brand names: Pegasys (peginterferon alfa-2a), ViraferonPeg (peginterferon alfa-2b)

Adult dose

Dose: Pegasys 180 micrograms SC once weekly (HBV/HCV per protocol; HCV largely superseded by DAAs)

Route: Subcutaneous

Frequency: Weekly

Clinical pearls

Chronic HBV: NICE TA96; current EASL guidelines support 48-week course in HBeAg-positive disease without cirrhosis
Chronic HCV: largely replaced by direct-acting antivirals (DAAs) per BHIVA/EASL
Specialist hepatology prescribing

Contraindications

Decompensated cirrhosis
Severe psychiatric illness/active suicidality
Autoimmune hepatitis
Severe cardiac disease
Pregnancy/breastfeeding
Severe haematological disease
Hypersensitivity

Side effects

Flu-like symptoms
Cytopenias (neutropenia, thrombocytopenia, anaemia)
Depression / suicidal ideation
Autoimmune disease (thyroid, vasculitis)
Retinopathy
Pulmonary fibrosis (rare)
Injection-site reactions

Interactions

Theophylline (reduced clearance)
Methadone (increased levels)
Telbivudine (peripheral neuropathy)

Monitoring

FBC
LFTs
TSH
Mental health (PHQ-9 or equivalent)
Viral load
Eye review (baseline)

Reference: BNF; NICE TA96; EASL clinical practice guidelines on HBV; BHIVA hepatitis guidelines; https://bnf.nice.org.uk/drugs/peginterferon-alfa/. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Pathways