Allopurinol (allopurinol)
Also sold as: Zyloric, Allorin, Algout, Alopur
Pregnancy
Cat C
Lactation
Caution
Schedule
H
Forms
Tablets 100 mg +1
Indications
- Gout — chronic prophylaxis and urate-lowering therapy
- Hyperuricaemia secondary to malignancy or chemotherapy (tumour lysis syndrome prophylaxis)
- Uric acid nephrolithiasis (uric acid kidney stones)
- Recurrent calcium oxalate nephrolithiasis with hyperuricosuria
Adult Dosing
Gout — initiation and titration
50–100 mg orally once daily (starting dose); increase by 100 mg every 2–4 weeks
Ongoing; titrate to target serum uric acid <6 mg/dL (or <5 mg/dL in tophaceous gout); maximum 900 mg/day
CRITICAL: Never initiate allopurinol during an acute gout attack — wait until the attack has fully resolved (at least 2–4 weeks). Starting allopurinol during an attack prolongs and worsens the attack. Continue colchicine or NSAID prophylaxis for 3–6 months after initiating allopurinol to prevent mobilisation flares.
Chemotherapy-induced hyperuricaemia (tumour lysis syndrome prophylaxis)
300–600 mg orally once daily
Start 1–2 days before chemotherapy; continue for 3–7 days post-chemotherapy
IV allopurinol available for patients unable to take orally. Rasburicase preferred for high-risk tumour lysis syndrome. Allopurinol 300 mg OD is standard; increase to 600 mg/day for high tumour burden.
Uric acid nephrolithiasis
200–300 mg orally once to twice daily
Long-term; combine with adequate hydration and urinary alkalinisation (sodium bicarbonate)
Target urinary uric acid excretion <600 mg/day. Alkalinise urine to pH 6.0–6.5 with potassium citrate or sodium bicarbonate to improve uric acid solubility.
Renal Dose Adjustment
| CrCl / eGFR | Dose Adjustment |
|---|---|
| CrCl 60–90 mL/min | 200 mg/day |
| CrCl 20–59 mL/min | 100–200 mg/day |
| CrCl <20 mL/min | 100 mg/day or every 2 days |
| Dialysis | 100 mg after each dialysis session. Oxypurinol (active metabolite) accumulates in renal impairment — dose reduction mandatory. |
Hepatic Adjustment
Reduce dose in severe hepatic impairment — monitor liver function tests. Mild-to-moderate impairment: use with caution; no specific dose established.
Pregnancy & Lactation
Pregnancy: Category C
Limited human data. Animal studies show no teratogenicity. Gout in pregnancy is rare — if urate-lowering therapy is essential, use with caution and only after risk-benefit discussion. Avoid if possible, especially in first trimester.
Lactation: Caution
Allopurinol and its active metabolite oxypurinol are excreted in breast milk. Reports of maculopapular rash in breastfed infants. Avoid use during breastfeeding if possible; if essential, monitor infant for rash and haematological abnormalities.
Top Drug Interactions
| Interacting Drug | Effect | Severity |
|---|---|---|
| Azathioprine and 6-mercaptopurine (6-MP) | Allopurinol inhibits xanthine oxidase which is the primary enzyme metabolising azathioprine and 6-MP — results in 3–4-fold increase in plasma levels causing severe myelosuppression, bone marrow failure. If combination is unavoidable, reduce azathioprine/6-MP dose by 75% and monitor FBC closely | Major |
| Ampicillin and amoxicillin | Increased incidence of skin rash (maculopapular) — approximately 3-fold increase; mechanism unclear. Avoid combination if possible; use alternative antibiotics | Moderate |
| Warfarin | Allopurinol inhibits hepatic metabolism of warfarin — increased anticoagulant effect and raised INR; monitor INR closely when starting, stopping, or dose-changing allopurinol | Moderate |
| Diuretics (thiazides, loop diuretics) and ACE inhibitors | Diuretics raise serum uric acid (reducing allopurinol efficacy) and increase risk of allopurinol hypersensitivity reactions (DRESS, SJS); ACEIs also increase hypersensitivity risk — monitor closely in patients on these combinations | Moderate |
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Side Effects
Common
- Nausea and gastrointestinal upset
- Skin rash — maculopapular (most common; STOP if any rash occurs and do not rechallenge without specialist review)
- Headache
- Drowsiness
- Acute gout flare on initiation (mobilisation flare — give colchicine prophylaxis)
Serious / Discontinue If
- Allopurinol hypersensitivity syndrome (AHS) — fever, rash, hepatitis, eosinophilia, renal failure; mortality up to 25% — immediate discontinuation required
- Severe cutaneous adverse reactions (SCAR) — Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), DRESS (drug rash with eosinophilia and systemic symptoms) — strongly associated with HLA-B*5801 allele
- Agranulocytosis and aplastic anaemia (rare)
- Hepatotoxicity — elevated liver enzymes, hepatic necrosis (rare)
- Vasculitis
Contraindications
- Acute gout attack (do not start or change dose during an attack)
- Previous allopurinol hypersensitivity or severe cutaneous reaction
- Concurrent azathioprine or 6-mercaptopurine without mandatory dose reduction
Available Indian Brands
| Brand | Manufacturer | Price (approx) |
|---|---|---|
| Zyloric 100 mg Tablets | GSK India | ₹28/10 tablets |
| Allorin 100 mg Tablets | Cipla | ₹22/10 tablets |
| Algout 100 mg Tablets | Mankind Pharma | ₹18/10 tablets |
Monitoring Required
- Serum uric acid — check at baseline and every 4 weeks during dose titration; target <6 mg/dL (<5 mg/dL in tophaceous gout)
- Serum creatinine and eGFR — at baseline and periodically (dose adjustment required in CKD)
- Full blood count (FBC) — baseline and periodically; especially if on azathioprine combination
- Liver function tests — baseline and at 3 months; monitor if hepatic disease
- Skin monitoring — counsel patient to report any rash immediately; stop allopurinol at first sign of rash
- HLA-B*5801 genotyping — mandatory before starting in Han Chinese, Thai, and Korean patients (high prevalence of this allele associated with severe cutaneous reactions)
- Gout flare frequency — assess clinical response; if flares persist despite target uric acid, review adherence and dosing
Patient Counseling Points
- Do NOT start allopurinol during a gout attack — wait until the attack has completely settled for at least 2–4 weeks.
- Allopurinol is a preventive medicine — it must be taken every day, even when you have no gout symptoms.
- You may get a gout attack in the first few months of starting allopurinol — this is normal as uric acid crystals dissolve. Your doctor will give you a separate medicine (colchicine) to prevent this.
- STOP allopurinol immediately if you develop any skin rash and contact your doctor urgently — even a mild rash can progress to a severe, life-threatening reaction.
- Take allopurinol with or after food to reduce stomach upset.
- Drink at least 2–3 litres of water daily to prevent kidney stones.
- Avoid alcohol and high-purine foods (red meat, organ meats, shellfish, beer) — these raise uric acid levels.
- Blood tests (uric acid, kidney function) are needed regularly to check if the dose is right.
- Allopurinol is a long-term medicine — do not stop it suddenly without consulting your doctor.
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Clinically reviewed by: Dr. Sanjay Kulkarni, MD (Medicine), DM (Clinical Immunology & Rheumatology)
Last reviewed: 2026-04-15
References
- Khanna D, et al. 2012 American College of Rheumatology guidelines for management of gout. Part 1: Systematic nonpharmacologic and pharmacologic therapeutic approaches to hyperuricemia. Arthritis Care Res (Hoboken). 2012;64(10):1431–1446.
- FitzGerald JD, et al. 2020 American College of Rheumatology Guideline for the Management of Gout. Arthritis Care Res (Hoboken). 2020;72(6):744–760.
- Hershfield MS, et al. Clinical pharmacogenomics: HLA genotyping for allopurinol in Asian patients. Arthritis Rheumatol. 2013;65(10):2566–2577.
- GSK India. Zyloric prescribing information. 2024.