Common uses of Allopurinol for gout and hyperuricemia
Allopurinol is a first-line urate-lowering therapy used to prevent gout attacks, shrink tophi, and reduce long-term joint damage. By inhibiting xanthine oxidase, it decreases production of uric acid, allowing urate crystals to dissolve gradually and minimizing new crystal formation. It is not a pain reliever and does not treat an acute flare, but it helps stabilize uric acid levels over time to prevent future attacks.
Beyond gout, Allopurinol helps prevent recurrence of uric acid kidney stones in people with hyperuricosuria, especially when dietary measures alone are insufficient. It is also used to manage chronic hyperuricemia related to kidney disease or certain genetic conditions that lead to overproduction of uric acid. In oncology, clinicians sometimes use Allopurinol to reduce uric acid spikes associated with tumor lysis syndrome when starting cytotoxic chemotherapy.
Clinical guidelines typically recommend Allopurinol as the initial xanthine oxidase inhibitor for most patients due to its effectiveness, affordability, and extensive track record. It is suitable for many patients, including those with chronic kidney disease, provided dosing is individualized and monitoring is consistent.
Dosage and direction: how to take Allopurinol safely
Allopurinol dosing is individualized and should be guided by a clinician. Treatment usually starts low and is titrated to reach a serum urate target below 6 mg/dL (or below 5 mg/dL in severe tophaceous gout). Typical adult starting doses are 100 mg once daily; in chronic kidney disease, clinicians may begin at 50 mg daily. The dose is increased gradually—often every 2 to 5 weeks—until the urate goal is reached, up to a maximum of 800 mg/day in divided doses in the U.S.
Do not initiate Allopurinol during an acute gout flare. If you are already taking it and a flare occurs, do not stop; continue the medication and treat the flare with appropriate anti-inflammatory therapy as directed by your clinician. When starting Allopurinol, many patients are prescribed low-dose colchicine, an NSAID, or low-dose corticosteroids for 3 to 6 months as prophylaxis against flare-ups that can occur during the early phase of urate lowering.
For uric acid kidney stone prevention, Allopurinol is combined with hydration and urine alkalinization strategies. In oncology settings (e.g., tumor lysis syndrome prophylaxis), dosing and timing differ and are determined by the oncology team, often starting 2 to 3 days before chemotherapy and continuing for 10 to 14 days, with careful lab monitoring.
Take Allopurinol after meals with a full glass of water to reduce stomach upset and support kidney excretion of urate. Maintain adequate daily fluid intake unless otherwise advised. Because oxypurinol (the active metabolite) is renally cleared, dosing is adjusted in kidney impairment. Regular checks of serum urate, kidney function, and liver enzymes help ensure safe, effective therapy.
Precautions before and during Allopurinol therapy
A rare but serious reaction called allopurinol hypersensitivity syndrome (AHS) can involve severe rash, fever, hepatitis, kidney injury, and eosinophilia. The risk is higher in certain genetic backgrounds, particularly carriers of HLA-B*58:01. Screening for HLA-B*58:01 is recommended in specific high-risk groups, notably people of Han Chinese, Thai, or Korean descent, especially if concomitant chronic kidney disease is present. If you develop a rash, stop Allopurinol and seek care immediately.
Tell your clinician about all medications and supplements. Special caution is needed with azathioprine and mercaptopurine, whose doses must be drastically reduced and closely monitored due to potentially severe toxicity when combined with Allopurinol. Additional vigilance is warranted with diuretics and ACE inhibitors (rash risk), warfarin (enhanced anticoagulation), and theophylline (levels may rise).
Allopurinol may be used in chronic kidney disease with cautious titration, but dehydration and sudden changes in renal function increase adverse event risk. Patients with liver disease may require lab monitoring to detect hepatotoxicity. In pregnancy and breastfeeding, risk–benefit should be individualized with a clinician; if treatment is needed, close monitoring is standard. Avoid excessive alcohol, which can raise uric acid and undermine therapy.
Contraindications to Allopurinol
Allopurinol is contraindicated in patients with prior serious hypersensitivity to allopurinol or oxypurinol, including Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), or AHS. Do not rechallenge after such reactions. Immediate discontinuation and emergency evaluation are required if severe cutaneous adverse reactions develop.
Concomitant pegloticase is generally contraindicated; xanthine oxidase inhibitors can mask rising urate levels that would otherwise alert clinicians to increased risk of infusion reactions with pegloticase. Use of Allopurinol with azathioprine or mercaptopurine is not absolutely contraindicated, but it requires expert management with substantial dose reduction and close monitoring due to life-threatening myelosuppression risk.
Possible side effects of Allopurinol
Common side effects include mild rash, itching, gastrointestinal discomfort (nausea, diarrhea, abdominal pain), headache, and drowsiness. These are often transient, but any new rash warrants urgent attention, as it can occasionally progress to more serious reactions. Lab abnormalities may include transient liver enzyme elevations or mild changes in blood counts.
Serious adverse reactions are uncommon but can be life-threatening. AHS, SJS/TEN, hepatitis, cholestatic jaundice, eosinophilia, vasculitis, interstitial nephritis, and severe bone marrow suppression have been reported. Risk factors include certain HLA genotypes, renal impairment, high starting doses, and diuretic use. Early recognition and drug discontinuation are critical. Seek immediate medical evaluation for fever, facial swelling, mucosal sores, dark urine, jaundice, widespread blistering, or peeling skin.
Gout flares may increase temporarily after starting Allopurinol due to mobilization of tissue urate. This is not an allergy and is mitigated by anti-inflammatory prophylaxis and slow dose titration. Staying on Allopurinol during flares, unless a serious adverse reaction occurs, supports long-term control.
Drug interactions: Allopurinol with azathioprine, warfarin, and more
Allopurinol inhibits xanthine oxidase, a key pathway for metabolizing azathioprine and 6-mercaptopurine. When combined, the dose of azathioprine/6-MP usually must be reduced to approximately 25–33% of the typical dose, with intensive monitoring for bone marrow suppression and infection. This combination should be managed only by clinicians experienced with these agents.
Warfarin’s anticoagulant effect may be enhanced, necessitating closer INR monitoring and possible dose adjustment. Theophylline levels can increase, particularly at higher Allopurinol doses. Concomitant use with ampicillin or amoxicillin is associated with a higher rate of rash. Cyclophosphamide and other myelosuppressive agents may increase hematologic toxicity; careful blood count monitoring is advised.
Didanosine levels rise significantly with Allopurinol, increasing the risk of toxicity; avoid coadministration. Cyclosporine concentrations may also increase. Aluminum hydroxide antacids can reduce Allopurinol absorption if taken simultaneously—separate administration times. Thiazide diuretics and ACE inhibitors can raise the risk of hypersensitivity reactions. Do not use Allopurinol concurrently with pegloticase; stop urate-lowering therapy before pegloticase initiation to avoid masking rising uric acid, which is used to detect nonresponse and reduce infusion reaction risk.
Missed dose: what to do if you forget Allopurinol
If you miss a dose, take it as soon as you remember unless it is close to the time of your next dose. If it is nearly time for the next dose, skip the missed dose and resume your regular schedule. Do not double up to “catch up.” Setting reminders can help maintain consistent urate control.
Overdose: recognizing and responding
Symptoms of Allopurinol overdose may include nausea, vomiting, diarrhea, dizziness, and rash; severe cases can involve kidney dysfunction or hepatitis. Seek emergency medical attention. Management is supportive, with aggressive hydration and correction of electrolyte abnormalities. Oxypurinol is dialyzable, so hemodialysis may be considered in select severe overdoses or significant renal impairment.
Storage and handling of Allopurinol
Store Allopurinol tablets at room temperature (ideally 20–25°C/68–77°F) in a tightly closed container, protected from moisture and excessive heat. Keep out of reach of children and pets. Do not use tablets that are discolored, chipped, or past their expiration date. Dispose of unused medication through take-back programs when available.
U.S. sale and prescription policy for Allopurinol
In the United States, Allopurinol is a prescription-only medication. It is not legal or safe to obtain Allopurinol without a valid prescription from a licensed clinician who has evaluated your health, medications, and goals for urate control. Responsible access typically occurs through in-person clinics, integrated health systems, or legitimate telehealth services that provide proper evaluation, diagnosis, and follow-up with lab monitoring.
Be cautious of websites offering to sell prescription drugs without a prescription; many are unregulated, may dispense counterfeit or substandard products, and can put your health at risk. Look for pharmacies accredited by the National Association of Boards of Pharmacy (NABP), such as those bearing the .pharmacy domain or listed on NABP’s Safe Pharmacy site. Insurance plans, discount programs, and manufacturer or nonprofit assistance can help make therapy affordable when prescribed appropriately.
Some health systems and telemedicine platforms streamline evaluation and prescription for gout management, but a clinician’s involvement is still required. We cannot assist in obtaining Allopurinol without a prescription, and any claims suggesting a workaround should be treated with skepticism. The safest, legal path is to consult a licensed provider who can confirm the diagnosis, order baseline labs, initiate a personalized dosing plan, and monitor your response over time.
