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Pharmacology · Other antivirals

Ribavirin !

An old broad-spectrum antiviral, now used with other hepatitis C drugs. It causes haemolytic anaemia and is strongly teratogenic.

Updated 2026-11-01

  • Class: Other antivirals
  • Enzyme: Inosine monophosphate dehydrogenase (IMPDH) and viral RNA polymerase
  • ATC code: J05AP01
  • WHO Model List of Essential Medicines

The figure shows ribavirin monophosphate bound to human IMPDH type II, one of its proposed targets.

Target in 3D: Inosine monophosphate dehydrogenase (IMPDH) and viral RNA polymerase. PDB structure 1NF7 (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Ribavirin is a guanosine analogue phosphorylated by cellular kinases. Its exact mechanism is not fully known; proposed actions include inhibiting IMP dehydrogenase (which depletes GTP), inhibiting the hepatitis C RNA polymerase, increasing viral mutations until the virus can no longer replicate, and shifting T-helper responses. It is not effective alone against hepatitis C.

  1. Cellular kinases phosphorylate ribavirin
  2. Ribavirin monophosphate inhibits IMPDH and depletes GTP
  3. The triphosphate may inhibit viral RNA polymerase and add mutations
  4. Viral replication falls (only in combination for hepatitis C)

Pharmacokinetics

Absorption
Oral, with food (a fatty meal increases exposure)
Distribution
Accumulates in red blood cells and other compartments; may persist for up to 6 months
Metabolism
Not a CYP450 substrate or inhibitor
Elimination
Slow; clearance falls in kidney disease
Half-life
About 12 days with repeated doses

Indications

  • Chronic hepatitis C, always with other drugs (historically with peginterferon alfa) Viral hepatitis →
  • Added to sofosbuvir-velpatasvir in hepatitis C with decompensated cirrhosis Cirrhosis →

Adverse effects

Common

  • Fatigue, fever, myalgia and headache
  • Nausea, loss of appetite and taste changes
  • Insomnia, irritability and depression
  • Rash, itching and hair loss

Contraindications

  • Pregnancy, and men whose female partners are pregnant
  • Haemoglobinopathies (thalassaemia major, sickle cell disease)
  • Use with didanosine
  • Significant or unstable heart disease (because of anaemia)

Key interactions

Didanosine
Contraindicated: fatal liver failure and other toxicities
Azathioprine
Severe pancytopenia
Zidovudine
More severe anaemia and neutropenia

What is monitored

  • Haemoglobin before treatment and at weeks 2 and 4, then as needed
  • Pregnancy test before, monthly during and for 6 months after treatment
  • Blood count, liver tests and kidney function
  • ECG if there is heart disease

Administration and safety

  • Oral, with food
  • Capsules swallowed whole; the oral liquid is shaken before use
  • Never used alone for hepatitis C

Nursing care

  • Check haemoglobin results before and early in treatment
  • Teach two reliable contraceptive methods for women and for male patients with female partners, during and for 6 months after
  • Ask about breathlessness, chest pain, palpitations or marked fatigue
  • Screen mood regularly

Pregnancy and breastfeeding

Contraindicated: it caused birth defects or fetal death in every animal species studied, at exposures far below human ones; pregnancy is avoided for 6 months after the last dose in women and in partners of treated men.

Test yourself

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

What is the main dose-related toxicity of ribavirin?

Haemolytic anaemia, usually starting in the first 1 to 2 weeks.

For how long after stopping ribavirin is pregnancy avoided?

Six months, in women and in the female partners of treated men.

Which human enzyme does ribavirin monophosphate inhibit?

Inosine monophosphate dehydrogenase (IMPDH), depleting GTP.

Which antiretroviral must never be combined with ribavirin?

Didanosine.

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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: DailyMed - RIBAVIRIN tablet, film coated (DailyMed (U.S. National Library of Medicine), 2026); Ribavirin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - SOFOSBUVIR AND VELPATASVIR tablet, film coated (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.