Pirfenidone
Antifibrotics
Antifibrotics
An oral antifibrotic for idiopathic pulmonary fibrosis; taken with food, it causes nausea, rash and sun sensitivity and needs liver tests.
Quick facts
- Group
- Antifibrotics
- Target
- Fibrogenic and inflammatory signalling in lung fibroblasts (molecular target not established)
- Used for
- Idiopathic pulmonary fibrosis
- Key effects
- Nausea · Rash and photosensitivity · Fatigue
- Monitor
- Liver tests · Skin · Nausea
- ATC
- L04AX05
No doses: the clinician sets them by the current guideline.
Mechanism of action
Pirfenidone is a pyridone with antifibrotic and anti-inflammatory effects in experimental models: it reduces fibroblast proliferation and the growth factors and collagen production that drive fibrosis. How it works in patients with idiopathic pulmonary fibrosis has not been established. In trials it slowed the decline in forced vital capacity.
- Lung injury drives fibroblasts to proliferate and make collagen
- Pirfenidone dampens fibrogenic growth-factor signalling
- Fibroblasts proliferate less and deposit less collagen
- The decline in lung function slows
Indications
- Idiopathic pulmonary fibrosis Interstitial lung disease →
Adverse effects
Common
- Nausea, dyspepsia, reflux, vomiting and abdominal pain
- Rash and photosensitivity
- Fatigue, dizziness and headache
- Decreased appetite and weight loss
- Upper respiratory infections, sinusitis and insomnia
Contraindications
- No absolute contraindications on the label
- Use with fluvoxamine is avoided
- Hypersensitivity to pirfenidone
Key interactions
- Fluvoxamine (strong CYP1A2 inhibitor)
- Much higher pirfenidone exposure; avoided
- Ciprofloxacin (moderate CYP1A2 inhibitor)
- Higher exposure; the pirfenidone dose is reduced
- Smoking and strong CYP1A2 inducers
- Lower exposure and possible loss of effect
What is monitored
- Liver tests (ALT, AST, bilirubin) before starting, monthly for the first six months and then every three months
- Skin: rash, blistering or sunburn-like reactions
- Nausea, appetite and weight
Administration and safety
- Oral capsules or tablets taken with food, at the same times each day
- The dose is built up gradually at the start; if treatment is interrupted for a long time it is restarted with the build-up
- Avoid sun and sunlamps: sunscreen and protective clothing
Pregnancy and breastfeeding
Human data are insufficient; animal studies did not show malformations, and use is weighed with the specialist.
Nursing care
- Teach sun protection every day, even on cloudy days
- Check liver tests and teach the signs of liver injury
- Teach to take each dose with food to lessen nausea and dizziness
- Advise stopping smoking, which also lowers drug levels
- Review the medicine list for fluvoxamine and ciprofloxacin
Pharmacokinetics
- Absorption
- Oral; food delays absorption and lowers the peak level, which improves tolerance
- Distribution
- Moderately bound to plasma proteins, mainly albumin
- Metabolism
- Liver, mainly by CYP1A2 (minor CYP2C9, 2C19, 2D6, 2E1); smoking induces CYP1A2 and lowers exposure
- Elimination
- Mostly in urine as the inactive 5-carboxy metabolite
- Half-life
- About 3 hours
Test yourself
Think of the answer, then tap the question to see it.
Which CYP enzyme mainly metabolises pirfenidone?
CYP1A2.
Why does smoking matter in a patient on pirfenidone?
Smoking induces CYP1A2, lowers pirfenidone exposure and may reduce its effect.
Which skin precaution is taught to every patient on pirfenidone?
Avoid sun and sunlamps, and use sunscreen and protective clothing (photosensitivity).
Connections
← Back to the class: Antifibrotics
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 - PIRFENIDONE- pirfenidone tablet, film coated (DailyMed (U.S. National Library of Medicine), 2025); Pirfenidone: MedlinePlus Drug Information (MedlinePlus (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.