Allopurinol – Uses, Dosage and Side Effects
Allopurinol is a medication used to lower uric acid levels in the blood. It is primarily prescribed for gout and certain kidney conditions.
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Allopurinol is a medication used to lower uric acid levels in the blood. It is primarily prescribed for gout and certain kidney conditions.
What is Allopurinol?
Allopurinol is a prescription medication belonging to the class of drugs known as xanthine oxidase inhibitors (uricostatics). It is used to permanently reduce elevated uric acid levels (hyperuricemia) in the blood. Allopurinol is one of the most widely used medications for the long-term management of gout and for the prevention of uric acid kidney stones.
Mechanism of Action
Allopurinol works by inhibiting the enzyme xanthine oxidase, which is responsible for the final step in purine metabolism in the body. Purines are components of DNA and are broken down during normal cell metabolism. Without inhibition of this enzyme, the end product is uric acid, which can crystallize at high concentrations in the blood and deposit in joints and kidneys. By inhibiting xanthine oxidase, less uric acid is produced, leading to lower uric acid levels in the blood.
Indications
- Chronic gout: Prevention of recurrent gout attacks and treatment of tophi (uric acid deposits in tissue)
- Hyperuricemia: Persistently elevated uric acid levels in the blood
- Uric acid or calcium oxalate kidney stones: Prevention of stone formation
- Tumor lysis syndrome: Prevention of a sharp rise in uric acid levels during chemotherapy
- Certain enzyme defects: e.g., Lesch-Nyhan syndrome
Dosage
The dosage of allopurinol is individually adjusted. Standard starting doses are 100 mg daily, which may be gradually increased to 300–600 mg daily, depending on uric acid levels and kidney function. A dose reduction is necessary in patients with impaired kidney function. The medication is typically taken once daily by mouth, preferably after a meal.
Side Effects
Allopurinol is well tolerated by most patients. Possible side effects include:
- Common: Skin rash (exanthema), gastrointestinal complaints (nausea, diarrhea)
- Occasional: Elevated liver enzymes, headache, dizziness
- Rare but serious: Stevens-Johnson syndrome or toxic epidermal necrolysis (severe skin reactions) – consult a doctor immediately at the first sign of skin changes
- At the start of therapy: Temporary worsening of gout attacks, as uric acid crystals dissolve and become mobilized
Drug Interactions
Allopurinol can affect the activity of certain other medications:
- Azathioprine and 6-mercaptopurine: Allopurinol inhibits their breakdown, which can significantly increase blood levels of these substances – dose adjustment is required
- Warfarin and other anticoagulants: Enhanced anticoagulant effect possible
- ACE inhibitors and thiazide diuretics: Increased risk of hypersensitivity reactions
- Ampicillin: Increased risk of skin rash
Usage Notes
Allopurinol should not be started during an acute gout attack, as this may prolong the attack. The treatment is intended for long-term prophylaxis and generally must be taken continuously. Patients should ensure adequate fluid intake (at least 2 liters per day) to promote the excretion of uric acid.
References
- Allopurinol Summary of Product Characteristics – European Medicines Agency (EMA), current version
- Richette P. et al. – 2016 updated EULAR evidence-based recommendations for the management of gout. Annals of the Rheumatic Diseases, 2017
- Stamp L.K. et al. – A new era for allopurinol use in gout management. Therapeutic Advances in Chronic Disease, 2019
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Related search terms: Allopurinol + Allopurinolum