Allopurinol

Allopurinol is a xanthine oxidase inhibitor prescribed for the long-term management of hyperuricemia, particularly in patients with gout, tophi, or uric acid nephrolithiasis. It works by reducing the production of uric acid in the body, thereby lowering serum and urinary uric acid levels. This medication is not intended for the treatment of acute gout attacks but serves as a prophylactic agent to prevent future episodes and complications associated with chronic hyperuricemia. Proper dosing and monitoring are essential to maximize therapeutic efficacy and minimize adverse effects.

Features

• Active ingredient: Allopurinol
• Available in tablet formulations (100 mg and 300 mg)
• Prescription-only medication
• Generic and brand-name versions available (e.g., Zyloprim)
• Requires gradual dose titration
• Long-term management therapy

Benefits

• Reduces frequency and severity of gout attacks over time
• Prevents formation of new urate crystals and tophi
• Lowers risk of uric acid kidney stone formation
• May help prevent joint damage from chronic gout
• Can reduce serum uric acid levels to target range (<6 mg/dL)
• Long-term prophylaxis for hyperuricemia-associated conditions

Common use

Allopurinol is primarily indicated for the management of:

• Chronic gout and gouty arthritis
• Hyperuricemia secondary to malignancies or chemotherapy
• Recurrent uric acid stone formation
• Prophylaxis in certain enzymatic disorders (e.g., Lesch-Nyhan syndrome)

It is not recommended for asymptomatic hyperuricemia unless specific clinical indications exist, such as frequent uric acid stone formation or aggressive chemotherapy protocols with high tumor lysis risk.

Dosage and direction

Dosage must be individualized based on serum uric acid levels, renal function, and clinical response. The typical adult starting dose is 100 mg once daily, with weekly increments of 100 mg until satisfactory uric acid control is achieved (usually 200-300 mg daily for mild gout, 400-600 mg daily for moderate to severe gout). Maximum daily dose is 800 mg. Doses exceeding 300 mg should be divided.

For patients with renal impairment:

• CrCl 10-20 mL/min: max 200 mg daily
• CrCl 3-10 mL/min: max 100 mg daily
• CrCl <3 mL/min: extend dosing interval to every 48+ hours

Take with plenty of water and preferably after meals to minimize gastric upset. Regular monitoring of serum uric acid levels, renal function, and liver enzymes is recommended during therapy.

Precautions

• Initiate therapy only after acute gout attack has completely subsided
• May precipitate acute gout attacks during initial treatment phase (prophylactic colchicine or NSAIDs recommended during first 3-6 months)
• Requires dose adjustment in renal impairment
• Periodic liver function tests recommended
• Use with caution in patients with history of hepatic disease
• May cause drowsiness; caution when operating machinery
• Maintain adequate hydration (2-3 L daily) to prevent renal stone formation
• Screen for HLA-B*5801 allele in patients of Asian descent (higher risk of severe cutaneous reactions)

Contraindications

• Hypersensitivity to allopurinol or any component of the formulation
• Patients who have experienced severe reactions to allopurinol (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis)
• Asymptomatic hyperuricemia (unless specific indications present)
• Concurrent use with didanosine
• Treatment of acute gout attacks (not an analgesic or anti-inflammatory agent)

Possible side effect

Common (≥1%):

• Skin rash (discontinue immediately if rash occurs)
• Nausea, vomiting, diarrhea
• Elevated liver enzymes
• Drowsiness, headache

Less common (<1%):

• Acute gout attacks (initial treatment period)
• Leukopenia, thrombocytopenia
• Peripheral neuropathy
• Alopecia
• Taste perversion

Rare but serious:

• Severe cutaneous adverse reactions (SCARs): Stevens-Johnson syndrome, toxic epidermal necrolysis
• Drug reaction with eosinophilia and systemic symptoms (DRESS)
• Hepatotoxicity, including fatal hepatic necrosis
• Vasculitis
• Bone marrow suppression

Drug interaction

Significant interactions include:

• Azathioprine/6-mercaptopurine: allopurinol inhibits metabolism, requiring 65-75% dose reduction
• Warfarin: may enhance anticoagulant effect
• Ampicillin/amoxicillin: increased risk of skin rash
• Diuretics: may decrease allopurinol efficacy
• Theophylline: increased serum levels
• ACE inhibitors: increased risk of hypersensitivity reactions
• Cyclophosphamide: enhanced bone marrow toxicity
• Didanosine: contraindicated due to increased toxicity

Missed dose

If a dose is missed, take it as soon as remembered unless it is almost time for the next dose. Do not double the dose to make up for a missed one. Maintain regular dosing schedule to ensure consistent uric acid control.

Overdose

Symptoms may include nausea, vomiting, diarrhea, and dizziness. In massive overdose, hepatic toxicity, bone marrow suppression, and acute renal failure may occur. There is no specific antidote. Treatment is supportive and includes gastric lavage if presented early, forced diuresis, and hemodialysis (allopurinol and metabolites are dialyzable). Monitor hematological, hepatic, and renal parameters closely.

Storage

Store at controlled room temperature (20-25°C/68-77°F). Keep container tightly closed and protect from moisture and light. Keep out of reach of children. Do not use after expiration date. Do not transfer tablets to other containers without proper labeling.

Disclaimer

This information is for educational purposes only and does not constitute medical advice. Allopurinol is a prescription medication that should be used only under the supervision of a qualified healthcare professional. Dosage and treatment duration should be individualized based on clinical assessment, laboratory monitoring, and patient-specific factors. Patients should not initiate, discontinue, or modify allopurinol therapy without consulting their physician. Report any adverse reactions to your healthcare provider immediately.

Reviews

Clinical studies and meta-analyses demonstrate allopurinol’s efficacy in maintaining serum uric acid levels below 6 mg/dL in approximately 80-90% of appropriately dosed patients. Long-term studies show significant reduction in gout attack frequency (70-80% reduction after 1 year), resolution of tophi, and prevention of joint damage. Patient satisfaction surveys indicate improved quality of life scores in chronic gout patients achieving target uric acid levels. The medication is generally well-tolerated with proper dosing and monitoring, though adherence can be challenging during the initial months due to possible gout flares. Most serious adverse reactions are rare when appropriate precautions are followed.