Types of medicine
What Is a Xanthine Oxidase Inhibitor? Gout Medicine
Xanthine Oxidase Inhibitor · say it: ZAN-theen OK-sih-dayz in-HIB-ih-terAlso written: XO inhibitor, urate-lowering therapy, uric acid lowering medicine
Short answer
A xanthine oxidase inhibitor is a medicine, such as allopurinol or febuxostat, that lowers uric acid by reducing how much the body makes.
What it means
Xanthine oxidase is an enzyme the body uses to make uric acid. A xanthine oxidase inhibitor blocks this enzyme, so less uric acid is produced. Allopurinol and febuxostat are the best-known examples. They are used long term to prevent gout attacks and in some other situations where uric acid is too high.
Labels explain several points. Gout flares can become more likely in the first months after starting, so another medicine is often given to prevent flares at first. Labels also warn about rare but serious skin reactions, ask you to report any rash, and list interactions with some medicines such as azathioprine and mercaptopurine.
These medicines prevent future gout attacks; they do not relieve an attack that is already happening. Pain relief for a flare usually comes from different medicines.
Where you may see it
- Allopurinol and febuxostat labels under 'Warnings'
- Gout clinic letters and treatment plans
- Leaflets under 'Other medicines and this medicine'
📄 How it looks on a report
Gout flares may occur after initiation of a xanthine oxidase inhibitor. Flare prophylaxis is recommended.
🙅 What it does not mean
- A flare soon after starting does not mean the medicine is failing; it is a known early effect.
- These medicines do not ease an attack that is already happening.
- Stopping them when you feel well can let uric acid rise again; ask before stopping.
🗒️ Questions to ask your doctor
💊 Medicines whose labels mention “Xanthine Oxidase Inhibitor”
Plain-English explanations of each medicine, from its official FDA label.
- Allopurinol
a xanthine oxidase inhibitor, a prescription medicine that acts on uric acid
🔗 Read more from trusted sources
- “Xanthine Oxidase Inhibitor” on MedlinePlus ↗
US National Library of Medicine
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