Allopurinol tablets are intended for people who need ongoing control of high uric acid levels. They help prevent gout attacks, uric acid kidney stones, and complications linked with some cancer treatments by lowering uric acid production.
Allopurinol, the active substance in Allopurinol tablets, is a xanthine oxidase inhibitor for people who need long-term control of excess uric acid.
Allopurinol is prescribed when lowering uric acid is clinically necessary. NICE recommends urate-lowering treatment for recurrent or troublesome gout, tophi, chronic gouty arthritis, and some kidney complications linked with urate excess. [2]
Its main preventative uses include:
Gout develops when uric acid levels remain high enough for crystals to form. The immune system reacts to these crystals, causing sudden pain, swelling, warmth, and restricted movement. Lowering uric acid addresses the biochemical cause rather than simply reducing the pain of one attack.
Tumour lysis syndrome can occur when cancer cells break down rapidly after chemotherapy. Their contents enter the bloodstream, and uric acid may rise sharply. In carefully selected oncology patients, Allopurinol can help reduce new uric acid production during this period.
| Clinical use | Preventative objective | Typical clinical focus |
|---|---|---|
| Recurrent gout | Reduce urate crystal formation | Long-term serum urate control |
| Uric acid stones | Reduce urinary uric acid burden | Prevention of recurrence |
| Tumour lysis risk | Limit uric acid production | Use around selected cancer treatments |
The drug is not suitable for every type of kidney stone. Stones caused by calcium, infection, or other substances require a different assessment.
Allopurinol belongs to the xanthine oxidase inhibitor class. Xanthine oxidase is an enzyme involved in the final stages of purine breakdown, a normal process that produces uric acid. By inhibiting this enzyme, Allopurinol lowers the amount of uric acid released into the bloodstream. [1]
The treatment is preventive. It does not work as an immediate painkiller during an acute gout attack, and it does not quickly remove inflammation from a swollen joint. Its purpose is to reduce uric acid over time so that new crystals form less readily and existing deposits can gradually dissolve. Serum urate monitoring helps assess progress. Acute flares may still require separate treatment.
Purines come from normal cell turnover and from some foods. Their breakdown produces hypoxanthine, xanthine, and finally uric acid. Allopurinol and its active metabolite, oxypurinol, inhibit xanthine oxidase at this stage.
Lower uric acid reduces the chance of monosodium urate crystals collecting in joints, soft tissues, and the urinary tract. The response is gradual because established crystal deposits take time to dissolve. A blood urate result can improve before a person feels a full reduction in gout symptoms.
A temporary flare can occur after treatment begins. This happens because changing urate levels can mobilise crystals from tissues. It does not automatically mean that Allopurinol is failing.
Allopurinol is not suitable for you if you have previously experienced a serious hypersensitivity reaction to allopurinol or oxypurinol. It also requires careful assessment if you have chronic kidney disease, liver disease, blood-count abnormalities, or a history of severe drug-related skin reactions.
Treatment requires special caution in people who:
An acute gout attack is not usually a reason to begin Allopurinol without an accompanying clinical plan. The decision depends on the individual’s history and anti-inflammatory treatment. The medicine also should not be used to treat every form of kidney stone.
This medicine may not be suitable if you have had a serious reaction to Allopurinol or oxypurinol. Tell a clinician before taking it if you have kidney or liver disease, blood-count problems, a previous severe medicine-related rash, or if you are pregnant, planning pregnancy, or breastfeeding. Medical advice is especially important if you take azathioprine, mercaptopurine, an ACE inhibitor, or a thiazide diuretic, or if you are receiving chemotherapy.
Many people tolerate Allopurinol without major problems, but adverse effects can occur. Mild nausea, diarrhoea, stomach discomfort, headache, or drowsiness may appear during treatment. Taking the tablet after food can reduce stomach irritation for some people.
A skin rash needs more attention. A mild rash can be the first sign of a serious hypersensitivity reaction, so it should not be ignored or self-treated with another medicine. Severe reactions may involve fever, facial swelling, swollen glands, liver injury, kidney injury, blistering, or mucosal ulcers.
Seek urgent medical help for:
Severe cutaneous reactions are uncommon but potentially life-threatening. The risk may be influenced by genetic factors, kidney function, age, and interacting medicines. HLA-B*58:01 testing is relevant for selected ethnic groups and clinical circumstances, based on pharmacogenetic guidance. [3]
The drug can also cause drowsiness in some people. This matters when driving, operating machinery, working at height, or performing tasks requiring constant attention.
Allopurinol tablets contain allopurinol as the active substance. Allopurinol is a xanthine oxidase inhibitor that lowers uric acid production. The amount per tablet is not specified here.
The intake amount is individually prescribed. There is no single fixed dose that suits every person.
Allopurinol is normally introduced carefully and adjusted according to serum urate and kidney function. People with reduced kidney function may need a lower regimen or slower adjustment. Blood tests help clinicians assess urate control, kidney function, liver function, and blood counts when clinically indicated.
Do not change the regimen because uric acid symptoms improve. Crystal deposits may remain even after the blood result reaches the target range.
Allopurinol belongs to the xanthine oxidase inhibitor category and lowers uric acid by reducing its production. This mechanism differs from urate-lowering approaches that act through another pathway.
Several habits can make treatment less reliable:
Hydration supports kidney health, while excess alcohol, dehydration, and rapid weight loss can worsen urate fluctuations. Diet alone may not control established gout, but reducing alcohol excess, sugary drinks, and large purine-heavy meals can support the treatment plan.
In clinical practice, doctors usually frame Allopurinol as long-term risk reduction rather than a short course for pain. The goal is sustained urate control and prevention of further crystal deposition.
A clinician will often review gout frequency, kidney function, uric acid results, joint findings, and current medicines before adjusting treatment. The dose may be increased gradually until the intended urate target is reached, with extra caution when renal function is reduced.
Patients sometimes judge the treatment too early. A flare during the first weeks can be discouraging, yet it may occur while the body is clearing established deposits. Stopping treatment after one flare can interrupt the process and leave urate levels uncontrolled.
Allopurinol does not usually impair concentration, but dizziness or drowsiness can occur. Do not drive, cycle on busy roads, or operate machinery until you know how the tablets affect you. The FDA prescribing information describes these possible effects and advises attention to individual response in its 2018 prescribing information.
Allopurinol can be taken with food or after food, and taking it after a meal may reduce stomach discomfort. Swallow it with water and keep the timing consistent from day to day. NICE guidance published in 2022 supports regular urate-lowering treatment as part of long-term gout management.
The most important high-risk combination is with azathioprine or mercaptopurine, because Allopurinol can markedly increase their toxicity. ACE inhibitors, thiazide diuretics, penicillin antibiotics, warfarin, and some supplements also need review before use together. The MHRA’s 2019 safety update stresses rapid assessment of suspected hypersensitivity reactions.
Swallow the tablet whole unless the prescriber or dispensing pharmacist has confirmed that splitting is suitable for the specific tablet. Do not crush or chew it without clear instructions, because this can affect accurate dosing and may make swallowing more difficult. Pharmacogenetic guidance from CPIC, published in 2013, also reinforces that Allopurinol treatment should be individualised according to clinical risk.
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I had repeated attacks in my big toe and started Allopurinol after blood tests. The first month included another flare, which worried me, but the attacks became less frequent after the regimen was adjusted.
I took the tablets for several months and found them easy to fit into my routine after breakfast. I still had to keep an anti-inflammatory plan for occasional flares, so I learned that Allopurinol was prevention rather than instant relief.
My uric acid improved, and I stopped waking with foot pain. I missed doses during a busy week and noticed symptoms returning, so using a regular reminder made a real difference.
I developed a rash soon after starting treatment and stopped taking further tablets until I received urgent medical advice. The reaction was taken seriously, and I did not restart it without a new clinical plan.
The tablets helped reduce attacks over time, but the adjustment period was frustrating. I had expected quick pain relief and needed a separate treatment for the flare that happened after starting.
