Allopurinol is a xanthine oxidase inhibitor prescribed for the long-term management of hyperuricemia, particularly in patients with gout, kidney stones, or those undergoing certain chemotherapy regimens. By reducing the production of uric acid, it addresses the underlying metabolic imbalance responsible for crystal deposition and inflammatory attacks. This medication requires consistent use and monitoring to achieve optimal therapeutic outcomes and prevent disease progression.

Features

• Active ingredient: Allopurinol
• Available in 100 mg and 300 mg tablet formulations
• Generic and brand-name versions (e.g., Zyloprim)
• Requires prescription in most jurisdictions
• Standard oral administration
• Not indicated for acute gout attacks

Benefits

• Reduces frequency and severity of gout attacks by lowering serum uric acid levels
• Prevents formation of new uric acid kidney stones and tophi
• May help preserve renal function in patients with chronic hyperuricemia
• Enables long-term management of underlying metabolic disorder
• Reduces need for NSAIDs and colchicine for acute flare prophylaxis
• May prevent tumor lysis syndrome in certain oncology patients

Common use

Allopurinol is primarily indicated for the management of chronic gout and conditions involving hyperuricemia. It is prescribed for patients with recurrent gout attacks, tophi, uric acid nephropathy, or renal stones. The medication is also used prophylactically in patients with leukemia, lymphomas, and malignancies who are receiving cancer therapy that may result in elevated uric acid levels. It is not intended for treatment of acute gout attacks and may initially exacerbate symptoms if started during an acute episode.

Dosage and direction

Initial dosage typically begins with 100 mg daily, gradually increasing by 100 mg weekly until target serum uric acid levels (<6 mg/dL) are achieved. Maintenance doses range from 200-600 mg daily for mild gout, with severe cases potentially requiring up to 800 mg daily divided into 2-3 doses. Maximum recommended daily dose is 800 mg. Dosing must be adjusted for renal impairment: for creatinine clearance 10-20 mL/min, maximum 200 mg daily; below 10 mL/min, maximum 100 mg daily or 100 mg every other day. Administration after meals with plenty of fluid is recommended to minimize gastric irritation and support renal excretion.

Precautions

Regular monitoring of serum uric acid levels, liver function tests, complete blood count, and renal function is essential during therapy. Patients should maintain adequate hydration (2-3 liters daily) to prevent xanthine crystal formation and renal calculi. Caution is advised when initiating therapy in patients with pre-existing renal impairment or hepatic disease. Skin reactions require immediate medical attention as they may indicate severe hypersensitivity syndrome. Gradual dose titration is necessary to avoid precipitating acute gout attacks during initial treatment phases.

Contraindications

Allopurinol is contraindicated in patients with known hypersensitivity to allopurinol or any component of the formulation. It should not be used during acute gout attacks unless patients are receiving concurrent anti-inflammatory therapy. The medication is contraindicated in patients who have experienced previous severe skin reactions to allopurinol, including Stevens-Johnson syndrome or toxic epidermal necrolysis. Concomitant use with azathioprine or mercaptopurine requires extreme caution and dose adjustment of these medications.

Possible side effect

Common adverse effects include skin rash (approximately 2% of patients), nausea, vomiting, diarrhea, and drowsiness. More serious but rare reactions include hepatotoxicity (elevated liver enzymes, jaundice), bone marrow suppression (leukopenia, thrombocytopenia), and severe hypersensitivity syndrome featuring fever, eosinophilia, rash, and organ involvement. Peripheral neuropathy, optic neuritis, and cataracts have been reported with long-term use. Approximately 25% of patients may experience acute gout flares during initial treatment months.

Drug interaction

Significant interactions occur with azathioprine and mercaptopurine (allopurinol inhibits their metabolism, requiring 65-75% dose reduction). Enhanced effects of warfarin and other coumarin anticoagulants may occur. Concurrent use with ampicillin/amoxicillin increases risk of skin rash. Thiazide diuretics may increase allopurinol toxicity risk in patients with renal impairment. Uricosuric agents (probenecid, sulfinpyrazone) may require dosage adjustment. Potential interaction with theophylline requires monitoring.

Missed dose

If a dose is missed, it should be taken as soon as remembered unless it is nearly time for the next scheduled dose. Doubling the dose to make up for a missed dose is not recommended. Consistent daily administration is important for maintaining reduced uric acid levels. Patients should maintain their regular dosing schedule and consult their physician if multiple doses are missed, as this may increase the risk of gout flare-ups.

Overdose

Symptoms of overdose may include nausea, vomiting, diarrhea, and dizziness. In severe cases, acute renal failure may occur. Management involves gastric lavage if presented early, supportive care, and adequate hydration to promote excretion. Hemodialysis may be effective in removing allopurinol and its active metabolite oxypurinol. There is no specific antidote. Medical attention should be sought immediately for suspected overdose, particularly in patients with pre-existing renal impairment.

Storage

Store at controlled room temperature (20-25°C or 68-77°F) in a tightly closed container. Protect from light and moisture. Keep out of reach of children and pets. Do not use after expiration date printed on packaging. Do not transfer tablets to other containers without proper labeling. Discard any medication that shows signs of deterioration or discoloration.

Disclaimer

This information is provided for educational purposes only and does not constitute medical advice. Allopurinol requires prescription and medical supervision. Individual patient response may vary. Healthcare professionals should reference official prescribing information for complete details. Patients should not adjust dosage or discontinue medication without consulting their physician. Proper diagnosis and monitoring are essential for safe and effective use.

Reviews

Clinical studies demonstrate allopurinol effectively reduces serum uric acid levels in 85-90% of patients when appropriately dosed. Long-term therapy shows significant reduction in gout attack frequency (70-80% reduction after first year) and tophus size. Patient satisfaction surveys indicate improved quality of life scores among compliant patients. Some reports note initial exacerbation of gout symptoms during therapy initiation. Dermatological reactions remain the most common reason for discontinuation (approximately 5% of patients). Renal function stabilization observed in hyperuricemic patients with chronic kidney disease.