allopurinol at a glance
Medicine class
Xanthine-oxidase inhibitor and urate-lowering medicine.
What it does
Reduces uric acid formation but does not relieve pain during an acute gout attack.
Taking the tablet
Swallow with water, preferably after food. Maintain adequate hydration if advised.
Important safety point
A new rash needs prompt assessment because rare severe skin reactions can occur.
What is allopurinol used for?
Allopurinol reduces uric acid formation when urate deposition has occurred or is predictably likely.
Gout, including gouty arthritis and tophi.
Uric-acid kidney stones and acute uric-acid kidney injury.
Recurrent mixed calcium-oxalate stones associated with excessive urinary uric acid when non-medicine measures have failed.
High uric acid associated with malignancy, cytotoxic treatment or myeloproliferative disease.
Selected inherited enzyme disorders causing urate overproduction.
Specialist, non-licensed use with thiopurines in inflammatory bowel disease or transplant care because this combination has a major interaction.
How does allopurinol work?
Allopurinol and its active metabolite oxipurinol inhibit xanthine oxidase, an enzyme involved in converting purines into uric acid. Lower uric acid levels reduce crystal formation in joints and the urinary tract and help protect the kidneys when uric acid production is high.
allopurinol preparations and strengths
Tablet
Route: Oral
Strengths: 100 mg, 200 mg, 300 mg
How to take allopurinol
Follow the dispensing label and prescriber’s instructions. Swallow the tablet with water, preferably after food. Do not stop or restart it independently, and check unfamiliar medicines or supplements with a pharmacist.
Taking it after food may help nausea.
Maintain adequate fluid intake when advised.
The break line on the selected Ipca tablet helps swallowing but does not confirm equal subdivision.
allopurinol side effects
Common or expected effects
- Feeling or being sick; taking the tablet after food may help.
- Diarrhoea.
- Skin rash, which must not be ignored because serious reactions can initially resemble a simple rash.
Get urgent medical advice
- Spreading, blistering or peeling rash; mouth, eye or genital sores; fever or flu-like illness.
- Facial or throat swelling, breathing difficulty, fainting or collapse.
- Yellow skin or eyes, dark urine or marked abdominal symptoms.
- Unexplained bruising or bleeding, persistent sore throat, fever or marked weakness.
allopurinol in pregnancy
Pregnancy evidence is limited. A specialist may use allopurinol when controlling the underlying condition outweighs potential risks. Arrange a medication review if pregnant, planning pregnancy or becoming pregnant; do not stop it independently.
allopurinol while breastfeeding
Allopurinol and oxipurinol pass into breast milk. It may be used when a clinician confirms that the baby is healthy, although product information is more cautious. Seek advice for a premature or unwell infant and report poor feeding, vomiting, diarrhoea or rash.
allopurinol interactions
Check prescriptions, over-the-counter medicines and supplements with a pharmacist or prescriber. Important interactions include:
Azathioprine or mercaptopurine
Can cause dangerous accumulation and potentially life-threatening bone-marrow suppression. Avoid unless managed by an experienced specialist with appropriate adjustment and monitoring.
Warfarin and other coumarin anticoagulants
The anticoagulant effect may increase, requiring closer clotting monitoring.
Common questions about allopurinol
Answers are fully visible for fast scanning and source review.
Does allopurinol relieve gout-attack pain?
No. It lowers uric acid to prevent future crystal accumulation but is not a painkiller for an acute attack.
Why can gout attacks happen after starting allopurinol?
Changing uric acid levels can temporarily mobilise existing crystals and trigger flares. This does not necessarily mean the medicine is failing.
More questions about allopurinol
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.