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[Pharmacology](https://durgical.com/en/pharmacology/) · Class

# Interferons

Protein medicines copied from the body's antiviral signals. Once central for hepatitis, they are now used mainly in multiple sclerosis and rare diseases.

Updated 2026-11-01

## What they are

Recombinant versions of human interferons. Interferon alfa (and its pegylated forms, injected weekly) treated hepatitis B and C and some cancers; direct-acting antivirals have largely replaced it for hepatitis C. Interferon beta is a treatment for relapsing multiple sclerosis, and interferon gamma reduces infections in chronic granulomatous disease.

## Mechanism of action

Interferons bind receptors on the cell surface and activate the JAK-STAT pathway. A STAT complex enters the nucleus and switches on dozens of genes that create an antiviral state: 2'-5' oligoadenylate synthetase activates RNase L, which cuts RNA, and a protein kinase phosphorylates eIF-2 and stops protein synthesis. They also raise MHC class I expression and shape the immune response.

Target: Interferon receptors (IFNAR1/IFNAR2 for type I; IFNGR1/IFNGR2 for interferon gamma)

## Key points

- Flu-like symptoms (fever, chills, myalgia, fatigue) after injections are almost universal.
- Depression and suicidal thoughts are the most important adverse effects: mood is checked at every visit.
- Myelosuppression (neutropenia, thrombocytopenia) and autoimmune thyroid disease: blood counts and thyroid function are followed.
- Interferon beta: relapsing multiple sclerosis. Interferon gamma: chronic granulomatous disease.
- Interferons are not absorbed by mouth; they are injected.

## Drugs in this class

- [**Interferon alfa** An injected protein that switches on antiviral defences. Once central for hepatitis B and C, it causes flu-like… Type I interferon receptor (IFNAR1/IFNAR2)](https://durgical.com/en/pharmacology/interferon-alfa/)
- [**Interferon beta** An injected immunomodulator for relapsing multiple sclerosis. It reduces relapses but does not cure the disease. Type I interferon receptor (IFNAR1/IFNAR2)](https://durgical.com/en/pharmacology/interferon-beta/)
- [**Interferon gamma** An injected immune activator that reduces serious infections in chronic granulomatous disease and slows severe… Interferon gamma receptor (IFNGR1/IFNGR2)](https://durgical.com/en/pharmacology/interferon-gamma/)

## Others in the class

- Peginterferon alfa-2a
- Peginterferon alfa-2b
- Peginterferon beta-1a
- Ropeginterferon alfa-2b

## Test yourself

Think of the answer, then tap the question to see it.

## Which signalling pathway do interferons activate?

The JAK-STAT pathway, which switches on genes that create an antiviral state.

## Which psychiatric adverse effect is most important with interferon alfa?

Depression, which can include suicidal thoughts.

## Which interferon is used in relapsing multiple sclerosis, and which in chronic granulomatous disease?

Interferon beta in multiple sclerosis; interferon gamma in chronic granulomatous disease.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 63 (McGraw Hill, 2023); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=L03AB) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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