Class
- Xanthine Oxidase Inhibitor
Indications
- Chronic management of gout to reduce uric acid levels.
- Prevention of recurrent kidney stones (uric acid stones).
- Treatment of hyperuricemia associated with cancer chemotherapy or radiation therapy.
Mechanism of Action
- Inhibits xanthine oxidase, an enzyme responsible for converting hypoxanthine and xanthine into uric acid.
- Reduces uric acid production, lowering serum and urinary uric acid levels.
Dosage and Administration
For Gout
- Starting dose: 100 mg daily.
- Maintenance dose: 200–600 mg daily (mild gout) or up to 800 mg daily (severe gout).
- Maximum dose: 800 mg daily, divided into 2–3 doses.
For Hyperuricemia in Cancer Therapy
- Starting dose: 600–800 mg daily, starting 1–2 days before chemotherapy.
For Kidney Stones
- Typical dose: 200–300 mg daily.
Administration
- Take after meals to reduce gastrointestinal upset.
- Drink plenty of fluids to prevent kidney stones and maintain hydration.
- Doses above 300 mg should be divided to reduce gastrointestinal side effects.
Forms Available
- Tablets: 100 mg, 300 mg
- Injectable form (for hospital use): 500 mg vial
Brand Names and Manufacturers
- Zyloprim (Prometheus Laboratories)
- Aloprim (injectable form)
- Generic versions widely available.
Cost
- Generally affordable, ranging from $10–$50 for a monthly supply, depending on brand and dosage.
Contraindications
- Hypersensitivity to allopurinol or any component of the formulation.
- Current acute gout attack (use may worsen symptoms if initiated during an attack).
Precautions
- Start at a low dose to minimize risk of gout flares when initiating therapy.
- Use with caution in patients with renal or liver impairment; dosage adjustment may be required.
- Discontinue immediately if a rash or other hypersensitivity reactions occur.
- Risk of severe skin reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis.
Side Effects
Common
- Rash
- Diarrhea
- Nausea
Less Common
- Liver enzyme elevations
- Drowsiness
- Acute gout flares (especially when starting therapy)
Rare but Serious
- Hypersensitivity syndrome (fever, rash, kidney/liver dysfunction)
- Stevens-Johnson syndrome or toxic epidermal necrolysis
- Bone marrow suppression
Drug Interactions
- Azathioprine and Mercaptopurine: Increased toxicity; reduce their dose significantly if used together.
- Warfarin: Enhanced anticoagulant effect; monitor INR closely.
- Diuretics (e.g., thiazides): Increased risk of hypersensitivity reactions.
- Antibiotics (e.g., amoxicillin): Increased risk of rash.
Monitoring Parameters
- Uric acid levels: Aim for a target of <6 mg/dL in gout patients.
- Liver and kidney function tests, especially in long-term use.
- Signs of hypersensitivity or severe skin reactions.
Patient Counseling Points
- Take after meals with plenty of fluids to reduce stomach upset.
- Do not stop taking allopurinol during a gout flare; continue as directed by your doctor.
- Inform your doctor of any rash, fever, or flu-like symptoms, as these may indicate a serious reaction.
- Avoid alcohol and high-purine foods (e.g., red meat, seafood) to help control uric acid levels.
- Be patient; full benefits may take weeks to months of consistent use.
- Always inform healthcare providers about allopurinol use before starting new medications.
FAQs About Allopurinol
Q1: How long does it take for allopurinol to work?
- It may take 1–2 weeks to lower uric acid levels and longer for gout symptoms to improve.
Q2: Can allopurinol be used during an acute gout attack?
- No, it should not be started during an acute attack as it may worsen symptoms. It is used for long-term prevention.
Q3: What happens if I miss a dose?
- Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double doses.
Q4: Can I drink alcohol while taking allopurinol?
- Alcohol can increase uric acid levels and reduce the effectiveness of allopurinol; it’s best to limit or avoid it.
Q5: Is allopurinol safe during pregnancy?
- Use only if clearly needed and prescribed by a doctor; discuss risks and benefits with your healthcare provider.
Q6: What should I do if I develop a rash while taking allopurinol?
- Stop taking allopurinol immediately and contact your doctor, as it may indicate a serious allergic reaction.
Q7: Can I eat a normal diet while on allopurinol?
- A low-purine diet (avoiding red meat, seafood, and certain alcohols) may help enhance its effectiveness.
Q8: How is allopurinol different from febuxostat?
- Both lower uric acid levels, but febuxostat may be preferred in patients who cannot tolerate allopurinol.
Q9: Are there natural alternatives to allopurinol?
- Lifestyle changes like diet modification and hydration can help but are not substitutes for medication.
Q10: Can allopurinol prevent kidney stones?
- Yes, it can prevent uric acid kidney stones by lowering uric acid levels in the urine.
Q11: Is allopurinol safe for long-term use?
- Yes, but regular monitoring of kidney and liver function is recommended.
Q12: Can I stop allopurinol if my symptoms improve?
- No, stopping may cause uric acid levels to rise and trigger gout attacks; always consult your doctor.
Q13: Does allopurinol cause weight gain?
- No, weight gain is not a known side effect.
Q14: Can children take allopurinol?
- Yes, in certain conditions like hyperuricemia due to cancer treatment, but under strict medical supervision.
Q15: What are high-purine foods to avoid while on allopurinol?
- Red meat, organ meats, shellfish, anchovies, and beer