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What is Allopurinol?
Allopurinol is a prescription medication used to lower uric acid levels in the blood. It is primarily prescribed to prevent gout attacks and manage chronic gout, but it can also be used to reduce the risk of certain types of kidney stones and to control uric acid levels in patients undergoing cancer treatment.
By lowering uric acid levels, allopurinol helps prevent the formation of sharp urate crystals in joints and tissues, which cause pain, swelling, and inflammation during gout flares. It is not used to treat an active gout attack, but rather to prevent future ones.
How It Works
Allopurinol works by inhibiting the enzyme xanthine oxidase, which plays a key role in the production of uric acid. Lowering uric acid levels over time reduces the risk of crystal formation and gout attacks, and can help dissolve existing deposits in joints and tissues.
Because uric acid reduction is gradual, patients may still experience gout flares in the first months of treatment. Doctors often prescribe anti-inflammatory medication during this period to reduce the risk of attacks while uric acid levels stabilize.
Dosage Information
Allopurinol is typically started at a low dose and increased gradually to avoid triggering gout flares. Common dosing guidelines include:
- Initial dose: 100 mg once daily
- Maintenance dose: 200–300 mg daily for mild gout, up to 800 mg daily for severe cases (divided doses)
Dosing is adjusted based on uric acid blood test results and kidney function. If you plan to buy allopurinol online, make sure you receive the correct strength and instructions. Generic allopurinol is widely available and can be a cheap and equally effective alternative to brand-name versions.
Side Effects
Common side effects of allopurinol include:
- Skin rash
- Diarrhea
- Nausea
- Drowsiness
Rare but serious side effects include severe allergic reactions such as Stevens–Johnson syndrome, liver problems, and bone marrow suppression. Seek medical attention immediately if you notice rash, fever, or swelling of the face or throat.
When you buy allopurinol online, ensure the pharmacy provides information about side effects and when to seek medical help.
Warnings & Interactions
Allopurinol should be used with caution in patients with kidney or liver disease. It can interact with medications such as azathioprine, mercaptopurine, certain antibiotics, and blood thinners. Adequate hydration is important to help prevent kidney stones.
Allopurinol is not for immediate relief of gout pain and should not be started during an active flare. If you need to stop or restart therapy after a break, consult your doctor to avoid complications.
If you buy allopurinol online, use a licensed pharmacy that verifies prescriptions and provides dosing guidance. Cheap generics are available, but safe sourcing is essential.
Frequently Asked Questions
It may take several weeks to months of daily use before uric acid levels are low enough to reduce gout flares.
No, starting allopurinol during an active attack can make symptoms worse. It’s best to wait until the flare has resolved.
Yes, limiting high-purine foods like red meat, shellfish, and alcohol can improve results and reduce the risk of gout flares.
Rarely, it can cause severe allergic reactions with rash, fever, and organ involvement. Seek medical attention immediately if these occur.
Yes, it’s often used alongside anti-inflammatory drugs during the first months to prevent flare-ups. Always follow your doctor’s instructions.
Yes, generic allopurinol works the same way and contains the same active ingredient as brand-name versions.
Medical Disclaimer
This website provides informational overviews of medications and does not offer medical advice, diagnosis, or treatment. Always consult a licensed healthcare provider before starting or changing any medication.
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This page was last medically reviewed: August 2025
Allopurinol should be started at a low dose and increased gradually under medical supervision to reduce the risk of gout flares.