Pharmacology · Xanthine oxidase inhibitors
Febuxostat !
A non-purine xanthine oxidase blocker for gout when allopurinol fails or cannot be used. It carries a warning about cardiovascular death.
Updated 2026-11-01
The figure shows cow's-milk xanthine dehydrogenase with febuxostat (code TEI-6720) filling the channel to the molybdenum site.
Mechanism of action
Febuxostat is a non-purine, selective inhibitor of xanthine oxidase. It sits in the channel that leads to the molybdenum active site, so hypoxanthine and xanthine cannot be oxidised to uric acid. At usual concentrations it does not block other enzymes of purine and pyrimidine metabolism.
- Non-purine drug enters the enzyme channel
- Xanthine oxidase cannot work
- Uric acid production falls
Pharmacokinetics
- Absorption
- Oral
- Metabolism
- Liver: conjugation by UGT enzymes and oxidation by cytochrome P450
Indications
- Chronic hyperuricaemia in gout, when allopurinol has not worked well enough, is not tolerated or is not advisable Gout →
Adverse effects
Common
- Abnormal liver tests
- Nausea
- Joint pain
- Rash
- Gout flares when starting
Contraindications
- Treatment with azathioprine or mercaptopurine
Key interactions
- Azathioprine and mercaptopurine
- Their levels rise and toxicity can be severe; the combination is contraindicated.
- Theophylline
- Febuxostat changes its metabolism (it is a xanthine oxidase substrate); used with caution.
What is monitored
- Serum uric acid
- Liver tests before starting and if symptoms appear
- Signs of heart attack or stroke
Administration and safety
- Oral tablet.
- Flare prophylaxis is recommended when it is started.
Nursing care
- Before starting, ask about heart disease, azathioprine or mercaptopurine.
- Teach the warning signs of heart attack and stroke (chest pain, shortness of breath, weakness on one side, trouble speaking).
- Teach to report dark urine, yellow skin or eyes, or a rash.
Pregnancy and breastfeeding
Human data are limited; the treating team weighs benefits and risks.
Test yourself
Think of the answer, then tap the question to see it.
When is febuxostat used instead of allopurinol?
When allopurinol has not lowered urate enough at the highest tolerated dose, is not tolerated, or is not advisable.
What is febuxostat's boxed warning?
A higher rate of cardiovascular death than allopurinol in people with gout and established cardiovascular disease.
Which two drugs are contraindicated with febuxostat?
Azathioprine and mercaptopurine.
Related drugs
Related conditions
← Back to the class: Xanthine oxidase inhibitors
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Febuxostat: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2019); DailyMed - FEBUXOSTAT tablet (DailyMed (U.S. National Library of Medicine), 2023); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.