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Allopurinol

Medication xanthine oxidase inhibitor other
Aka: Zyloric, Zyloprim
Brands seen in Singapore: Zyloric, Apo-Allopurinol, YSP Allopurinol, GP-Allopurinol
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
Lowering uric acid to prevent gout attacks and urate stones
When to take
NHS: usually once a day · started after an attack settles
Take with
Water · with or after food · HealthHub: 2–3 litres a day
Pros & cons
Pros
  • NHS: fewer gout attacks, less joint damage over time
  • HealthHub: also used for uric acid (urate) stones
  • NHS: one tablet a day, usually 100mg to 300mg
Cons
  • More gout attacks in the first months (NHS, HealthHub)
  • HealthHub: rare severe skin reactions (sjs, ten, dress)
  • Nausea, being sick and stomach upset are common (NHS)
Sources
  1. HSA — Listing of Registered Therapeutic Products (data.gov.sg open dataset, 5,511 rows, full dataset pulled once via datastore_search and filtered locally) · read 2026-08-27
    what it says
    “9 registered allopurinol products, every one Forensicclassification 'Prescription Only': SIN06060P/SIN06061P ZYLORIC TABLET 100 mg and 300MG, SIN06247P/SIN06248P APO-ALLOPURINOL, SIN07051P/SIN17004P YSP ALLOPURINOL, SIN17232P GP-ALLOPURINOL, SIN05804P and SIN06219P plain ALLOPURINOL TABLET — all tablets”
  2. NHS Medicines A-Z — Allopurinol (brand names: Zyloric, Uricto), 'About allopurinol', page last reviewed 23 January 2023 · read 2026-08-27
    what it says
    “Allopurinol is a medicine used to lower levels of uric acid in your blood … These crystals can form around your joints, which cause the swollen and painful symptoms of gout … only available on prescription.”
  3. NHS Medicines A-Z — Allopurinol, 'About allopurinol' key facts · read 2026-08-27
    what it says
    “During the first few months of treatment, as allopurinol starts to work, you may get more gout attacks … Usually, you'll start allopurinol after an acute attack of gout has completely settled.”
  4. NHS Medicines A-Z — Allopurinol, 'How and when to take allopurinol' · read 2026-08-27
    what it says
    “Allopurinol comes as 100mg to 300mg tablets that you take every day … your doctor may increase your dose (up to 900mg daily in severe cases) … Swallow your allopurinol tablet with water, ideally after food.”
  5. NHS Medicines A-Z — Allopurinol, 'Who can and cannot take allopurinol' · read 2026-08-27
    what it says
    “tell your pharmacist or doctor before taking it if you: … are of Han Chinese, Thai or Korean origin … have problems with your liver or kidneys … currently have an attack of gout … have thyroid problems”
  6. NHS Medicines A-Z — Allopurinol, 'Side effects of allopurinol': Stevens-Johnson syndrome · read 2026-08-27
    what it says
    “Stevens-Johnson syndrome is a rare side effect of allopurinol. It causes flu-like symptoms, followed by a red or purple rash that spreads and forms blisters … more likely to happen in the first 8 weeks”
  7. NHS Medicines A-Z — Allopurinol, 'Taking allopurinol with other medicines and herbal supplements' · read 2026-08-27
    what it says
    “aspirin or medicines used to help prevent blood clots (anticoagulants), such as warfarin; any antibiotics; medicines used to reduce your immune response; tablets that make you pee more (diuretics) such as furosemide or ACE inhibitors”
  8. NHS Medicines A-Z — Allopurinol, interactions: aluminium hydroxide antacids · read 2026-08-27
    what it says
    “If you take aluminium hydroxide (found in some antacids such as Maalox and Mucogel), leave a 3-hour gap between the aluminium hydroxide and your allopurinol dose.”
  9. HealthHub (MOH Singapore / National Medication Information workgroup) — Allopurinol leaflet, article last reviewed 4 June 2026: uses · read 2026-08-27
    what it says
    “Allopurinol is used to prevent gout … Allopurinol reduces the production of uric acid, thus lowering the uric acid levels in the body. Allopurinol is also used in the treatment of uric acid stones”
  10. HealthHub — Allopurinol leaflet: how it is taken and fluid intake · read 2026-08-27
    what it says
    “This medication should be taken with or after food to reduce stomach upset. Take this medication with plenty of water … Drink enough water (2-3 litres of water a day) unless your doctor has advised you to restrict fluid intake.”
  11. HealthHub — Allopurinol leaflet: common side effects and early gout flares · read 2026-08-27
    what it says
    “Diarrhea … Upset stomach … When allopurinol is started for gout prevention, the chances of having gout attacks may be higher initially.”
  12. HealthHub — Allopurinol leaflet: rare but serious skin reactions (links to the HSA consumer guide 'Safe use of allopurinol') · read 2026-08-27
    what it says
    “very rarely, a bad skin reaction known as Stevens-Johnson syndrome (SJS), Toxic epidermal necrolysis (TENs) or Drug reaction with eosinophilia and systematic symptoms (DRESS) may happen. This can cause serious health problems that may sometimes be fatal.”
  13. HealthHub — Allopurinol leaflet: HLA-B*5801 gene testing before starting · read 2026-08-27
    what it says
    “Your doctor may conduct a gene testing before starting this medication as individuals with a specific gene type (HLA-B*5801) or poor kidney function may be more likely to suffer serious skin reactions.”
  14. HealthHub — Allopurinol leaflet: food and medicines to tell the doctor about · read 2026-08-27
    what it says
    “What food or medication should I avoid when I take or use this medication? Inform your doctor if you are taking: Warfarin, Azathioprine, Mercaptopurine”
  15. FDA DailyMed SPL — Allopurinol tablets, Highlights of Prescribing Information (label effective 8 Jul 2024), read via the openFDA drug-label API · read 2026-08-27
    what it says
    “Patients with normal kidney function: Initial dosage is 100 mg orally daily. Increase by 100 mg weekly increments until serum uric acid of 6 mg/dl or less is reached (maximum 800 mg daily).”
  16. FDA DailyMed SPL — Allopurinol tablets, section 7 Drug Interactions · read 2026-08-27
    what it says
    “The following drugs may increase the risk of serious skin reactions: bendamustine, thiazide diuretics, ampicillin and amoxicillin. Capecitabine: Avoid concomitant use. Mercaptopurine or Azathioprine: Reduce mercaptopurine or azathioprine dose as recommended in the respective prescribing information.”
  17. FDA DailyMed SPL — Allopurinol tablets, section 5.1 Skin Rash and Hypersensitivity · read 2026-08-27
    what it says
    “The HLA-B*58:01 allele is a genetic marker for severe skin reactions … The frequency of this allele is higher in individuals of African, Asian (e.g., Han Chinese, Korean, Thai), and Native Hawaiian/Pacific Islander ancestry”
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Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.