Allopurinol lowers uric acid in the blood. It is used to prevent gout attacks and uric acid kidney stones, and to protect the kidneys during some cancer treatments. It is a long-term preventive medicine — it does not treat an attack that has already started, and starting it during one can make things worse.
What is Allopurinol?
Allopurinol is Schedule 3 in South Africa and available under many names — Cipla Allopurinol, Austell Allopurinol, Puricos, Redurate, Bexacos, Zorikos and Lessuric:
| Strength | Typical use |
|---|---|
| 100 mg | Starting dose, and small increments |
| 150 mg | Intermediate |
| 300 mg | Common maintenance dose |
Being dispensed one brand rather than another is ordinary generic substitution.
Allopurinol is a xanthine oxidase inhibitor. Understanding what that means explains almost everything about how it is used.
The body constantly breaks down purines — from food and from normal cell turnover — into uric acid, using an enzyme called xanthine oxidase. Allopurinol blocks that enzyme, so less uric acid is produced.
Gout happens when uric acid levels exceed the point at which it stays dissolved. It then forms needle-like crystals in joints, triggering intense inflammation — the classic hot, swollen, exquisitely painful joint, often the base of the big toe.
Here is the critical point about how allopurinol works. Lowering blood uric acid causes crystals already deposited in the joints to slowly dissolve. That is the cure — but crystals dissolving can itself trigger an attack. This is why:
- Allopurinol commonly causes gout attacks when first started, which feels like the medicine failing when it is actually working.
- A preventive anti-inflammatory or colchicine is usually prescribed alongside it for the first months to cover that period.
- It is started at a low dose and increased gradually.
Understanding this prevents the most common mistake: stopping allopurinol because you had an attack after starting it. That is expected, temporary, and stopping restarts the whole process.
What is Allopurinol commonly used for?
- Preventing gout attacks — the main use, taken every day, long term.
- Dissolving tophi, the visible uric acid deposits that form in longstanding gout.
- Uric acid kidney stones, and preventing their recurrence.
- Tumour lysis syndrome, preventing the uric acid surge when cancer treatment destroys many cells rapidly.
- Some enzyme disorders causing uric acid overproduction.
- Chronic kidney disease with high uric acid, in some cases.
It is preventive, not a painkiller. During an acute attack, treatment is an anti-inflammatory such as naproxen or etoricoxib, colchicine, or a steroid — allopurinol does nothing for the pain.
Treatment aims at a target uric acid level, checked by blood test, with the dose adjusted until it is reached. Many people are left on a dose that never quite gets there, and continue having attacks as a result. If you are still getting attacks, ask what your uric acid level is and whether the dose should be increased.
It is usually lifelong. Stopping allows uric acid to climb and attacks to return.
How Allopurinol fits into this medicine category
| Group | Examples | Role |
|---|---|---|
| Xanthine oxidase inhibitors | Allopurinol, febuxostat | Lower uric acid production; prevent gout |
| Uricosurics | Probenecid | Increase uric acid excretion |
| Anti-inflammatories | Naproxen, etoricoxib, indomethacin | Treat the acute attack |
| Colchicine | Colchicine | Treats and prevents attacks |
| Corticosteroids | Prednisone | Acute attacks where NSAIDs are unsuitable |
| Simple analgesics | Paracetamol | Pain relief; no effect on uric acid |
See the pain, inflammation and musculoskeletal medicines hub.
What to check before using Allopurinol
Do not start it during an acute attack, unless your doctor specifically directs it. Wait until the attack has settled.
Do not stop it during an attack if you are already established on it. Stopping and restarting makes attacks more likely.
Drink plenty of water, which helps the kidneys clear uric acid.
Tell your doctor or pharmacist if you:
- Have kidney disease. The dose depends on kidney function, and this is the most important check.
- Have liver disease.
- Are of Han Chinese, Thai or Korean descent, or have African ancestry. A gene variant, **HLA-B*5801**, is associated with a much higher risk of severe skin reactions to allopurinol, and is more common in these groups. Testing is available in some settings and is worth asking about.
- Take azathioprine or mercaptopurine. This is a serious interaction — allopurinol blocks their breakdown, and levels can rise to dangerous, potentially fatal concentrations. Doses must be drastically reduced.
- Take warfarin, theophylline, ciclosporin, or ACE inhibitors or diuretics.
- Take amoxicillin or ampicillin, which cause rash more often alongside allopurinol.
- Have thyroid problems.
- Are pregnant, planning pregnancy or breastfeeding.
Expect blood tests — uric acid to check the dose is working, plus kidney and liver function.
Diet helps but rarely suffices. Reducing alcohol (beer especially), sugary drinks with fructose, red meat and shellfish genuinely lowers uric acid — but usually not enough alone in someone who needs allopurinol. Weight loss and treating high blood pressure also help.
Possible cautions and when to ask a pharmacist or doctor
Common effects are rash, nausea, and gout attacks in the first months of treatment.
Stop the medicine and seek medical attention immediately if you develop a rash. This is the single most important warning with allopurinol. Most rashes are mild, but allopurinol is one of the medicines most associated with severe cutaneous adverse reactions — Stevens-Johnson syndrome, toxic epidermal necrolysis and DRESS syndrome. These are rare but can be fatal, and they usually begin in the first two months.
Seek immediate medical attention for:
- Any rash, particularly a spreading, painful or blistering one.
- Peeling skin, or sores in the mouth, eyes or genitals.
- Fever with a rash, or swollen glands.
- Facial swelling.
- Yellowing of the eyes or skin.
- Fever, sore throat or mouth ulcers, or unusual bruising or bleeding.
- Much less urine than usual.
- Severe tiredness with a rash and fever — possible DRESS syndrome, which can appear weeks after starting.
Do not simply continue and hope a rash settles. Stopping early is what prevents these reactions becoming severe.
Contact your doctor if you are still having attacks after several months, if you have not had your uric acid level checked, or if side effects are troubling.
Related medicine guides
- Browse Pain, Inflammation & Musculoskeletal Medicines guides
- Read: Prednisone used for
- Read: Donapan used for
Frequently asked questions
What is allopurinol used for? Preventing gout attacks by lowering uric acid, and preventing uric acid kidney stones. It is taken daily, long term.
What is allopurinol 300 mg used for? A common maintenance dose for gout prevention, usually reached after starting at 100 mg and increasing gradually.
Will it help my gout attack now? No. It is preventive and does nothing for pain. Acute attacks need an anti-inflammatory, colchicine or a steroid.
Why did I get an attack after starting it? Falling uric acid causes existing crystals to dissolve, which can trigger an attack. This is expected, temporary, and a sign it is working — do not stop.
How long do I take it for? Usually indefinitely. Stopping allows uric acid to rise and attacks to return.
What should I do if I get a rash? Stop the medicine and seek medical attention immediately. Allopurinol is associated with rare but serious skin reactions, usually in the first two months.
Do I still need to watch my diet? Diet helps — less alcohol, fructose, red meat and shellfish — but is usually not enough alone in someone who needs allopurinol.
Why do I need blood tests? To check your uric acid has reached target, and to monitor kidney and liver function. If you still get attacks, ask what your level is.