1. Clinical & Scientific Overview
Allopurinol (TIP-MED-000112, Reference Code [7.10]) is classified under
Pain, Inflammation, Rheumatology & Gout Medicines (Ch 07) as a Xanthine Oxidase Inhibitor (Purine Analogue; Metabolised to Active Oxypurinol); Urate-Lowering Agent.
Within the Indian regulatory and compendial framework, it is governed under Schedule H Prescription Drug (To be sold by retail on the prescription of a Registered Medical Practitioner only — Drugs Rules 1945).
Representative Indian Market Examples (Edition 2.7 Ch 07 [7.10], p. 83): Zyloric (GSK), Ciploric (Cipla), Zyrik (Ipca), Gudloric — Strengths & Dosage Forms: Oral Uncoated Scored Tablets: 100 mg, 300 mg
Oral Uncoated Scored Tablets: 100 mg, 300 mg
3. Mechanism of Action & Pharmacodynamics
Xanthine Oxidase Inhibitor (Purine Analogue; Metabolised to Active Oxypurinol); Urate-Lowering Agent acting on target receptor/enzyme pathways in Pain, Inflammation, Rheumatology & Gout Medicines (Ch 07): clinical efficacy is mediated via Xanthine Oxidase Inhibitor (Purine Analogue; Metabolised to Active Oxypurinol); Urate-Lowering Agent for Chronic management of gout and hyperuricaemia (tophaceous gout, recurrent gout flares ≥2/year, urate nephrolithiasis); prevention of tumour lysis syndrome hyperuricaemia during cancer chemotherapy. (Not generally recommended for mild asymptomatic hyperuricaemia without gout or renal stones)..
4. Therapeutic Indications & Evidence-Supported Uses
- Chronic management of gout and hyperuricaemia (tophaceous gout, recurrent gout flares ≥2/year, urate nephrolithiasis)
- prevention of tumour lysis syndrome hyperuricaemia during cancer chemotherapy
- (Not generally recommended for mild asymptomatic hyperuricaemia without gout or renal stones)
🇮🇳 Jurisdiction & Indication Note: Indications and schedules reflect Indian compendial and regulatory records (CDSCO / Indian Pharmacopoeia & NFI / NLEM 2022). Where international reference labels (US FDA DailyMed / NCBI StatPearls) are cited for pharmacokinetic or mechanistic parameters, international approvals do not automatically imply CDSCO approval in India.
5. Educational Dosage Context, Formulations & Administration
Educational Dosing & Regimen Summary: General Adult Reference: Start Low, Go Slow! Initiate at 100 mg once daily (50 mg once daily in CKD Stage 3–4), and titrate by 50–100 mg every 2–4 weeks to achieve target Serum Uric Acid <6.0 mg/dL (<5.0 mg/dL in tophaceous gout). Typical maintenance: 100–300 mg/day (doses >300 mg/day are divided BD after meals). Follow physician prescription.
Administration & Meal Timing: Take AFTER food (usually after breakfast or lunch) with a full glass of water to minimise gastric irritation. | Once daily after breakfast/lunch (for doses ≤300 mg).
6. Pharmacokinetics, Metabolism & Renal/Hepatic Adjustment
Absorption, distribution, metabolism, and excretion follow class pharmacokinetic profile; verify patient renal/hepatic function.
Renal: Strictly renal-function dependent! Active metabolite oxypurinol (t1/2 ~18–30 h in normal kidneys; >70 h in renal failure) is excreted renally; starting at high doses (300 mg) in CKD strongly precipitates fatal SJS/DRESS! Initiate at 50 mg/day if eGFR <30–45 mL/min and titrate very slowly by 50 mg every 4 weeks. Hepatic: Monitor LFTs; reduce dose in hepatic disease.
Renal: Strictly renal-function dependent! Active metabolite oxypurinol (t1/2 ~18–30 h in normal kidneys; >70 h in renal failure) is excreted renally; starting at high doses (300 mg) in CKD strongly precipitates fatal SJS/DRESS! Initiate at 50 mg/day if eGFR <30–45 mL/min and titrate very slowly by 50 mg every 4 weeks. Hepatic: Monitor LFTs; reduce dose in hepatic disease.
Renal: Strictly renal-function dependent! Active metabolite oxypurinol (t1/2 ~18–30 h in normal kidneys; >70 h in renal failure) is excreted renally; starting at high doses (300 mg) in CKD strongly precipitates fatal SJS/DRESS! Initiate at 50 mg/day if eGFR <30–45 mL/min and titrate very slowly by 50 mg every 4 weeks. Hepatic: Monitor LFTs; reduce dose in hepatic disease.
7. Contraindications, Precautions & High-Risk Warnings
- CRITICAL GOUT FLARE RULE: (1) If the patient is NOT currently taking allopurinol and presents with an acute painful gout attack, treat the acute pain/inflammation first (NSAID/colchicine/steroid) or initiate low-dose allopurinol with mandatory flare prophylaxis (low-dose colchicine 0.5 mg OD or NSAID for 3–6 months), as rapid drops in serum uric acid mobilize joint crystals and trigger paradoxical gout flares! (2) If a patient is ALREADY taking chronic allopurinol and develops an acute gout flare, DO NOT STOP ALLOPURINOL—continue the same dose and treat the acute flare concurrently! High risk of severe cutaneous reactions (HLA-B*58:01 allele).
Key Clinical Precautions: Renal: Strictly renal-function dependent! Active metabolite oxypurinol (t1/2 ~18–30 h in normal kidneys; >70 h in renal failure) is excreted renally; starting at high doses (300 mg) in CKD strongly precipitates fatal SJS/DRESS! Initiate at 50 mg/day if eGFR <30–45 mL/min and titrate very slowly by 50 mg every 4 weeks. Hepatic: Monitor LFTs; reduce dose in hepatic disease.
8. Adverse Effects Profile
- Maculopapular pruritic skin rash (2%—must discontinue immediately at first sign of any rash!), paradoxical acute gout flare during initial 1–3 months, mild nausea/diarrhoea.
- Allopurinol Hypersensitivity Syndrome (AHS), DRESS Syndrome (Drug Reaction with Eosinophilia and Systemic Symptoms), and Stevens-Johnson Syndrome / Toxic Epidermal Necrolysis (SJS/TEN—occurs mostly within first 2–8 weeks; carries 20–25% mortality!), hepatotoxicity, bone marrow suppression.
- Monitor for severe hypersensitivity, organ toxicity, or dose-limiting adverse events.
9. Major Drug–Drug, Drug–Food & Drug–Herb Interactions
- LIFE-THREATENING INTERACTION WITH AZATHIOPRINE (Azoran) & 6-MERCAPTOPURINE: Azathioprine and 6-MP are inactivated by xanthine oxidase—combining Allopurinol with Azathioprine causes a 4-fold accumulation of 6-MP and fatal bone marrow aplasia/pancytopenia! (Avoid combination, or manage strictly under specialist direction with appropriate specialist-directed azathioprine dose adjustment and close CBC monitoring)
- Ampicillin and Amoxicillin triple the incidence of skin rashes when combined with allopurinol
- Enhances effect of Warfarin and Theophylline
- ACE inhibitors (captopril/enalapril) and thiazides slightly increase hypersensitivity risk in CKD
10. Clinical Monitoring, Patient Counselling & Storage
Clinical & Laboratory Monitoring: Monitor clinical response, baseline renal/hepatic parameters, and relevant serum biomarkers.
Pharmacist Patient Counselling Points:
- Patient Counselling Checklist: 3 Essential Counselling Points for Zyloric: (1) Stop immediately at the very first sign of any skin rash, itching, eye redness, lip blisters, or fever and see your doctor—a mild rash can rapidly progress to a severe life-threatening skin reaction; (2) Allopurinol is NOT a painkiller for an acute gout attack—it is a long-term preventative that dissolves uric acid crystals over months (and if a joint attack happens while on it, keep taking Zyloric alongside the doctor's pain tablet); (3) Drink 8–10 glasses of water daily.
- Meal & Clock Timing Instruction: Take AFTER food (usually after breakfast or lunch) with a full glass of water to minimise gastric irritation. (Once daily after breakfast/lunch (for doses ≤300 mg).)
- Missed Dose Protocol: Take after food as soon as remembered on the same day; never double the dose.
- Geriatric Dispensing Pearl: Never start an elderly CGHS patient directly on a 300 mg tablet of Zyloric! Always verify that therapy starts at 50 mg–100 mg OD based on eGFR, and confirm the patient is not taking Azathioprine (Azoran).
Storage, Stability & Dispensing Safeguards: Store below 25°C–30°C in original moisture- and light-resistant packaging out of reach of children. Available forms: Oral Uncoated Scored Tablets: 100 mg, 300 mg
11. Visual Pharmacology & Mechanism Diagram (svg-v339-01-adme-12-step-journey)
12. Authoritative References, Regulatory Sources & Editorial Disclaimer
Primary Compendial & Guideline Reference: Indian Pharmacist Desk Reference — Professional Edition 2.7 (2026–27) • Ch 07 [7.10] (p. 83)
Official Verification Portals: Indian Pharmacopoeia Commission (IPC) & National Formulary of India (NFI) • Central Drugs Standard Control Organization (CDSCO) • Ministry of Health & Family Welfare — NLEM 2022 • NCBI Bookshelf / StatPearls Pharmacology Reference • DailyMed (US FDA Official Prescribing Reference)
Last Medically & Pharmaceutically Reviewed: 2026-11-10 • Verification Status: HANDBOOK_SOURCE_CONTENT
Educational & Clinical Disclaimer: This reference profile is published solely for pharmacy education, academic study, and professional clinical reference. It does not substitute for patient-specific clinical judgement, qualified specialist oncology/medical supervision, or official CDSCO/IP prescribing information. Never self-medicate with prescription, Schedule H/H1/X, NDPS, or oncology medicines.
13. Related Reference Monographs, Educational Guides & Visual Concept
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