Allopurinol

How Does Allopurinol Work?

Allopurinol works by inhibiting xanthine oxidase, the enzyme responsible for the final steps of uric acid production in the body. After being metabolized in the liver to its active form — oxypurinol — it blocks xanthine oxidase from converting hypoxanthine to xanthine and xanthine to uric acid. This reduces the total amount of uric acid released into the bloodstream.

When blood uric acid levels fall below the saturation point of 6 mg/dL, uric acid crystals that have accumulated in joints and soft tissue over time begin to dissolve. Over months to years of consistent therapy, this crystal dissolution eliminates the source of gout attacks. Allopurinol does not treat acute gout flares — it has no anti-inflammatory properties — but over time it eliminates the condition that causes them.

Because allopurinol blocks xanthine oxidase — the same enzyme that metabolizes azathioprine and 6-mercaptopurine — it has a critical drug interaction with these immunosuppressants. When used together without dose reduction, azathioprine or 6-MP levels can rise to toxic levels. This interaction must always be considered before prescribing allopurinol.

How Hard Is It to Find Allopurinol in Stock?

Allopurinol oral tablets are generally widely available and are not in national shortage as of 2026. The medication has a findability score of 90/100 — one of the highest among gout medications — reflecting its multiple generic manufacturers and consistent demand. Large chain pharmacies (Walmart, Costco, CVS, Walgreens) routinely stock 100 mg and 300 mg tablets.

Despite overall good availability, individual pharmacy stock-outs do occur. The 200 mg tablet strength is notably less commonly stocked than 100 mg or 300 mg. Rural patients may face more limited options. The intravenous formulation (Aloprim) has historically been subject to supply disruptions in hospital settings.

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Who Can Prescribe Allopurinol?

Allopurinol is not a controlled substance, so any licensed prescriber can write a prescription. The vast majority of allopurinol prescriptions are written by primary care providers and internists, not specialists, reflecting how routinely manageable gout is in primary care settings.

• Primary Care Physicians / Family Medicine Doctors — most common prescribers; handle routine gout management
• Internal Medicine Physicians — manage gout alongside comorbidities like hypertension, CKD, and metabolic syndrome
• Rheumatologists — gout specialists; manage complex cases, tophaceous gout, and patients failing first-line therapy
• Nephrologists — prescribe for gout in CKD patients and for recurrent kidney stone management
• Nurse Practitioners (NPs) and Physician Assistants (PAs) — can prescribe independently in most states; commonly manage gout in primary care and urgent care
• Oncologists — prescribe allopurinol for tumor lysis syndrome prevention in chemotherapy patients

Telehealth availability: Allopurinol can be prescribed via telehealth in all 50 states. Because it's not a controlled substance, no in-person visit is required before obtaining a prescription. Major telehealth platforms including Teladoc, MDLive, and Amazon Clinic regularly prescribe allopurinol for gout management.

Is Allopurinol a Controlled Substance?

No. Allopurinol is not a controlled substance and has no DEA scheduling. It has no potential for abuse, dependence, or misuse. This means allopurinol prescriptions are not subject to the restrictions that apply to controlled substances — they can be called in by phone, transmitted electronically, have unlimited refills at the prescriber's discretion, and can be prescribed via telehealth in all 50 states without in-person visit requirements.

Patients taking allopurinol for chronic gout typically receive a prescription for 90-day supplies with multiple refills. There are no state-by-state prescribing restrictions, no PDMP (Prescription Drug Monitoring Program) reporting requirements, and no quantity limits imposed by regulatory bodies. Insurance plans may impose quantity limits independently of DEA requirements, but these are uncommon for allopurinol.

Common Side Effects of Allopurinol

The most commonly reported adverse effects (occurring in >1% of patients) include:

• Nausea (most common GI side effect; reduced by taking with food)
• Diarrhea
• Elevated liver function tests (usually transient and mild)
• Drowsiness or dizziness
• Gout flares during the first months of therapy (expected as crystals mobilize; treat concurrently with colchicine or NSAIDs)

Serious Side Effects — Stop Allopurinol Immediately If These Occur

• Any skin rash — early warning of potentially fatal SJS/TEN or DRESS syndrome
• Stevens-Johnson syndrome (SJS) / Toxic Epidermal Necrolysis (TEN) — life-threatening blistering skin reactions; risk elevated in HLA-B*5801-positive patients
• DRESS syndrome — fever, widespread rash, eosinophilia, multi-organ involvement
• Hepatotoxicity — jaundice, right upper quadrant pain, dark urine
• Myelosuppression — unusual bruising/bleeding, persistent infections, fatigue

Final Thoughts on Allopurinol

Allopurinol is one of medicine's great success stories: a 60-year-old medication that remains the first-line treatment for one of the most common forms of inflammatory arthritis, available generically at remarkably low cost, and effective for millions of patients worldwide. For the vast majority of gout patients who can tolerate it, allopurinol — taken consistently and titrated to a uric acid target of ≤6 mg/dL — can essentially eliminate gout attacks over time.

The key challenges with allopurinol are adherence (fewer than half of patients remain on it at 12 months), appropriate titration (many patients are started and left on subtherapeutic doses), and awareness of its serious but rare drug interactions and hypersensitivity risks — particularly in patients of Southeast Asian or African American descent who may carry the HLA-B*5801 allele.

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