RHEUMATOLOGY · CRYSTAL ANALYSIS ACTIVE · TOPIC: GOUT & HYPERURICEMIA · REF: ACR / EULAR / FDA
The Crystal Scope Rheumatology reference · U.S. edition
Rheumatology · Crystal arthropathy

Gout is not a disease of rich men who eat too much. It is a crystal-driven inflammatory arthritis with a clear target.

Roughly 9 million American adults live with gout — the most common inflammatory arthritis in the country — and the incidence is rising. The mechanism is well understood: when serum uric acid exceeds its solubility limit, monosodium urate crystals deposit in joints, activate the NLRP3 inflammasome, and trigger an intense flare. Modern treatment is straightforward, effective, and underused.

13 min read
ACR/EULAR-aligned
MSU · NLRP3 · <6 mg/dL
9M+
American adults live with gout — the most common inflammatory arthritis in the U.S.
4×
Higher prevalence in men — though the gap narrows after menopause in women.
6.8
mg/dL solubility threshold — above this level, urate can crystallize in tissues.
< 6.0
Treat-to-target serum urate goal — and below 5 mg/dL for severe or tophaceous disease.
Section 01 · The mechanism

Uric acid, MSU crystals, and the inflammasome that turns them into a flare.

Gout begins with uric acid — the end product of purine metabolism in humans. Most mammals express an enzyme called uricase that breaks uric acid down further into allantoin, which is highly soluble and easily excreted. Humans lost the uricase gene during evolution, which is why our uric acid levels run 3 to 10 times higher than those of other mammals, and why we are one of the few species that develops gout.

Purines come from two sources: dietary intake (red meat, organ meats, shellfish, beer) and endogenous turnover of nucleic acids. They are metabolized by xanthine oxidase into uric acid. In a healthy person, about two-thirds of uric acid is excreted by the kidneys and one-third by the gut. In most patients with gout, the problem is underexcretion — the kidneys do not clear uric acid efficiently — rather than overproduction. This is why dietary restriction alone rarely controls gout: the dietary contribution is typically a small fraction of the total urate pool.

The solubility threshold is approximately 6.8 mg/dL. Above that level, urate in the blood and tissues can crystallize into needle-shaped monosodium urate (MSU) crystals. These crystals deposit preferentially in cooler peripheral joints (the first metatarsophalangeal joint, the midfoot, the ankle, the knee) and in soft tissues, where lower temperatures and pH reduce urate solubility.

Crystals alone do not cause a flare. Many people with hyperuricemia never have a gout attack. What triggers the acute inflammatory response is the activation of the NLRP3 inflammasome inside macrophages that have engulfed MSU crystals. Inflammasome activation leads to the release of interleukin-1β (IL-1β) — a potent pro-inflammatory cytokine — which recruits neutrophils and produces the intense pain, swelling, redness, and warmth of an acute flare. This mechanism is the reason colchicine and IL-1 inhibitors work: they interrupt the crystal-driven inflammatory cascade at the level of the inflammasome or its downstream signaling.

Section 02 · Clinical stages

Four stages — from silent hyperuricemia to chronic tophaceous gout.

Stage 01

Asymptomatic hyperuricemia

Serum urate is elevated (> 6.8 mg/dL) but no crystals have caused an inflammatory response. Most people in this stage never develop gout — but the higher the urate, the higher the risk. Treatment is generally not recommended at this stage unless there is a specific indication.

Stage 02

Acute flare

Sudden onset of severe joint pain, often overnight, reaching peak intensity within 24 hours. The first MTP joint ("podagra") is involved in about 50% of first attacks. The affected joint is red, hot, swollen, and exquisitely tender. Even light contact with a bedsheet can be unbearable.

Stage 03

Intercritical gout

The period between flares, when the patient is asymptomatic. Early in the disease, this period can last months to years. Over time, flares become more frequent, more prolonged, and involve more joints — which is why starting urate-lowering therapy after the first flare is now recommended for many patients.

Stage 04

Chronic tophaceous gout

After years of untreated hyperuricemia, deposits of MSU crystals called tophi form in joints, tendons, bursae, and soft tissues. They can cause joint destruction, chronic pain, deformity, and in some cases nerve compression. Reversible with sustained urate-lowering therapy — but it can take months to years.

Serum urate · treatment target
Illustrative · 24-month course
10 8 6 4 mg/dL 0 Month 3 Month 6 Month 12 Month 18 Month 24 6.8 · crystal threshold < 6.0 · target ULT START flare flare
Serum urate Treat-to-target goal Crystallization threshold
Section 03 · Acute flare treatment

Stopping the attack — and why timing matters as much as choice.

Treatment started within 24 hours of onset is dramatically more effective than treatment started after 48 hours. Patients who recognize the early signs of a flare and have medication on hand do substantially better than those who wait to call their doctor.

FIRST-LINE · NSAIDs

Full-dose NSAIDs

Indomethacin, naproxen, ibuprofen, and celecoxib are all effective for acute flares when taken at full anti-inflammatory doses. Indomethacin has historically been the standard, but naproxen and ibuprofen have fewer GI side effects and are just as effective.

Avoid in patients with kidney disease (eGFR < 30), peptic ulcer disease, or on anticoagulation. Not for use in patients with heart failure. Do not combine with colchicine.

indomethacin · naproxen · ibuprofen · celecoxib · etoricoxib (outside U.S.)
FIRST-LINE · ANTI-INFLAMMATORY

Colchicine

A microtubule inhibitor that disrupts inflammasome-driven neutrophil activation. Most effective when started within 12 to 24 hours of flare onset. Low-dose colchicine (1.2 mg followed by 0.6 mg one hour later, then 0.6 mg once or twice daily) is as effective as high-dose with far fewer GI side effects.

Dose adjustment required for renal or hepatic impairment. Dangerous interactions with CYP3A4 inhibitors — clarithromycin, ketoconazole, ritonavir, verapamil, cyclosporine. Can cause severe myopathy, bone marrow suppression, and in rare cases, death. Also used as flare prophylaxis when starting urate-lowering therapy.

colchicine 0.6 mg tablets
FIRST-LINE · STEROIDS

Corticosteroids

Oral prednisone (30–40 mg daily for 3–5 days, then taper) or intra-articular triamcinolone for a single accessible joint. Preferred when NSAIDs and colchicine are contraindicated — particularly in patients with kidney disease, heart failure, or GI bleeding risk.

Intra-articular steroid injection is highly effective and avoids systemic side effects. Rule out septic arthritis before injecting a joint. Avoid long-term systemic steroids — use short courses only.

prednisone · prednisolone · methylprednisolone · intra-articular triamcinolone
REFLEX · IL-1 INHIBITORS

IL-1 blockade

Anakinra and canakinumab are IL-1 inhibitors that directly target the inflammasome-driven inflammatory cascade. Reserved for severe, refractory flares or for patients who cannot tolerate or have failed NSAIDs, colchicine, and steroids. Particularly useful in hospitalized patients or those with multiple comorbidities.

Expensive, and often requires prior authorization. Canakinumab is FDA-approved for gout flares. Anakinra is used off-label.

canakinumab (Ilaris) · anakinra (Kineret)

Do not start, stop, or change urate-lowering therapy during an acute flare. This is one of the most common errors in gout management. If a patient is already on ULT, continue it — stopping it during a flare can prolong the attack. If they are not on ULT, wait until the flare has fully resolved (usually 2 to 4 weeks) before starting it — with the exception that starting ULT during a well-controlled flare is acceptable in some protocols when accompanied by adequate anti-inflammatory prophylaxis. The safest and most common approach is to treat the flare, wait for resolution, then start ULT with prophylactic anti-inflammatory cover.

Ice and rest help. Topical cold packs for 20 minutes several times a day reduce pain and inflammation. Elevation of the affected limb, when possible, also helps. Aspirin is not appropriate for gout flares — at low doses it can raise uric acid levels by interfering with renal urate excretion.

Section 04 · Urate-lowering therapy

Long-term control — the medications that actually change the disease.

Urate-lowering therapy (ULT) is the only treatment that reduces the frequency of flares, dissolves tophi, and prevents joint damage. It is indicated for any patient with two or more flares per year, tophi, chronic gouty arthropathy, or urate kidney stones.

FIRST-LINE · XANTHINE OXIDASE INHIBITOR

Allopurinol

The worldwide first-line ULT and one of the most cost-effective medications in medicine. Inhibits xanthine oxidase, reducing uric acid production. Start at a low dose (100 mg daily, or 50 mg in renal impairment) and titrate every 2 to 4 weeks until the target urate level is reached. Most patients need 300 mg daily; some require 600 to 800 mg.

The most important safety consideration is allopurinol hypersensitivity syndrome (AHS) — a rare but potentially fatal reaction more common in patients with renal impairment, in older adults, and in certain ethnic populations (Han Chinese, Thai, Korean). Screening for HLA-B*58:01 is recommended in high-risk populations before starting. Never start during an acute flare without anti-inflammatory cover.

allopurinol 100 mg · 300 mg tablets
SECOND-LINE · XANTHINE OXIDASE INHIBITOR

Febuxostat

A more selective xanthine oxidase inhibitor, effective in patients who cannot tolerate allopurinol. No dose adjustment required in mild-to-moderate renal impairment, which is an advantage. Available in 40 mg and 80 mg tablets.

Carries a boxed warning for cardiovascular events based on the CARES trial — patients with established cardiovascular disease should be managed carefully, and allopurinol remains preferred first-line. More expensive than allopurinol. Not recommended in patients with prior hypersensitivity to allopurinol.

febuxostat (Uloric) · 40 mg · 80 mg
RESCUE · PEGYLATED URICASE

Pegloticase

A pegylated recombinant uricase that directly degrades uric acid into allantoin, which is highly soluble and easily excreted. Reserved for severe, refractory tophaceous gout in patients who have failed or cannot tolerate standard ULT.

Given as an IV infusion every 2 weeks. High rate of infusion reactions and loss of efficacy due to anti-drug antibodies — patients are premedicated with antihistamines and corticosteroids, and urate levels are monitored before each infusion. Combination with methotrexate improves response rates and durability. Very expensive.

pegloticase (Krystexxa) · IV every 2 weeks
PROPHYLAXIS · WHEN STARTING ULT

Flare prophylaxis

When ULT is started, urate levels drop — and this shift can paradoxically trigger flares by destabilizing existing crystal deposits. All patients starting ULT should receive anti-inflammatory prophylaxis for at least 3 to 6 months, and sometimes longer if tophi are present.

Colchicine 0.6 mg once or twice daily is the standard. Low-dose NSAIDs or low-dose prednisone (< 10 mg/day) are alternatives when colchicine is contraindicated. Prophylaxis is continued until urate is at target and the patient has been flare-free for at least 3 months.

colchicine 0.6 mg daily · naproxen 250 mg twice daily · prednisone ≤ 10 mg daily
Section 05 · Drug interactions

Gout medications interact with surprisingly many common drugs.

Both the drugs used to treat gout and the drugs that can raise uric acid are important to know. The table below is partial — always review with a pharmacist or prescriber.

Selected clinically significant interactions
Not exhaustive · verify with a pharmacist
Interacting drug Severity Management
Azathioprine / 6-mercaptopurine Avoid Allopurinol blocks xanthine oxidase, which metabolizes azathioprine — the combination can cause severe bone marrow suppression. If unavoidable, reduce azathioprine dose by 60–75% with close monitoring.
Clarithromycin / ketoconazole / ritonavir Avoid with colchicine Potent CYP3A4 inhibitors dramatically increase colchicine levels — risk of severe myopathy, bone marrow suppression, and death. Reduce colchicine dose or choose an alternative antimicrobial.
Thiazide diuretics (HCTZ) Monitor Thiazides raise uric acid and increase allopurinol hypersensitivity risk. Use with caution, particularly when starting allopurinol.
Metformin Reference No direct interaction with gout drugs — but the same transporter-mediated principles apply (e.g., OCT2 for metformin renal clearance). A useful parallel to how these interactions are managed appears in this reference on Metformin side effects.
Amoxicillin / ampicillin Monitor Increased risk of non-allergic rash when combined with allopurinol. Usually mild, but worth discussing with the prescriber before combining.
Warfarin Monitor INR Allopurinol can increase warfarin effect. INR should be checked more frequently when starting, stopping, or adjusting allopurinol.
ACE inhibitors / ARBs Monitor Both can raise uric acid modestly and increase risk of allopurinol hypersensitivity. Often still appropriate to co-prescribe with monitoring.
Statins (simvastatin, atorvastatin) Monitor CK Colchicine can increase risk of statin-induced myopathy. Monitor for muscle pain and CK elevation; alternative statins (rosuvastatin, pravastatin) have fewer interactions.
Low-dose aspirin (< 2 g/day) Avoid for flare Aspirin raises uric acid by inhibiting renal tubular secretion — not appropriate for gout flare treatment. High-dose aspirin has the opposite effect. Use NSAIDs other than aspirin or steroids for flares.
Cyclosporine / tacrolimus Monitor Both raise uric acid and interact with colchicine. Transplant patients require specialist management.
The two most important interactions to remember. First, allopurinol + azathioprine can cause fatal bone marrow suppression — this combination should be avoided or managed by a specialist. Second, colchicine + strong CYP3A4 inhibitors can cause fatal colchicine toxicity — this is the most common serious drug interaction in gout care. Everything else on the table is manageable with monitoring.
Section 06 · What to watch for

Signs that require urgent medical evaluation.

Urgent evaluation

Not every hot, swollen joint is gout. Some require emergency treatment.

Fever, chills, or systemic illness with an acutely swollen joint. Possible septic arthritis — a medical emergency. Requires joint aspiration and antibiotics. Do not assume it is gout.
First-ever attack of monoarthritis in a patient without confirmed gout. Septic arthritis must be ruled out before treating as gout, especially if the patient is immunosuppressed.
Rash, fever, eosinophilia, or acute kidney injury after starting allopurinol. Possible allopurinol hypersensitivity syndrome — a life-threatening reaction requiring immediate discontinuation and emergency evaluation.
Severe GI symptoms, muscle weakness, or cytopenias on colchicine. Possible colchicine toxicity — particularly with renal impairment or interacting medications. Can be fatal.
Sudden severe flank or back pain with decreased urine output. Possible urate nephrolithiasis or acute urate nephropathy — requires urgent evaluation, especially in tumor lysis syndrome.
Cardiovascular symptoms in a patient on febuxostat. Febuxostat carries a boxed warning for cardiovascular events. New chest pain, shortness of breath, or neurological symptoms require prompt evaluation.
Progressive joint destruction or nerve compression from large tophi. Requires rheumatology evaluation. Sustained urate-lowering can resolve tophi but may take months to years.
Section 07 · Diet and lifestyle

What actually helps — and why diet alone rarely controls gout.

Diet can lower uric acid, but not enough to replace medication for most patients. A strict purine-restricted diet reduces serum urate by roughly 1 mg/dL — meaningful as an adjunct, but insufficient on its own when the target is below 6 mg/dL and the patient is starting from 8 or 9. This is why every major guideline recommends urate-lowering therapy for patients with recurrent flares, and treats diet as a supporting intervention.

The dietary changes with the strongest evidence. Reducing or eliminating beer (and to a lesser extent other alcohol) has the largest single effect. Limiting sugar-sweetened beverages and fructose — both of which raise uric acid through ATP depletion in the liver — is also important. Reducing organ meats, red meat, and shellfish lowers purine load. Increasing dairy (especially low-fat) actually lowers urate. Coffee consumption is associated with lower urate in observational studies. Weight loss, when overweight, reduces urate and flare frequency.

What does not work. Cherry extract and cherry juice concentrate are widely marketed for gout, with modest evidence at best. Celery seed, apple cider vinegar, and various "gout detox" supplements have no meaningful evidence of benefit. Vitamin C at 500–1000 mg/day has a small urate-lowering effect that is not clinically significant in patients with established gout. These interventions are not harmful in most cases but should not displace effective pharmacotherapy.

For patients on multiple chronic medications — which is common in gout, given its association with hypertension, diabetes, obesity, and chronic kidney disease — keeping the medication list current and checking pharmacy-level pricing is worth doing. A live comparison across licensed U.S. sellers, like the one shown for Metformin delivery, demonstrates how the same generic medication can vary in price from one pharmacy to the next. Buying commonly prescribed medications online — such as through a resource that explains buy Metformin online — is a legitimate option when done through verified sellers, and the same principles apply to gout medications.

Before filling from any seller — online or local — verify them. A working VIPPS seal that resolves to a live NABP record, a real U.S. street address, and a prescription requirement that cannot be waived. Gout medications are taken for years; the pharmacy you choose should be one you can hold accountable.

Section 08 · Questions

Five asked most often at the rheumatology clinic.

Q·01 What causes gout? +
Gout is caused by the deposition of monosodium urate (MSU) crystals in joints and soft tissues. When serum uric acid rises above approximately 6.8 mg/dL, urate can crystallize. These crystals activate the NLRP3 inflammasome and trigger an intense inflammatory response — producing the sudden, severe joint pain characteristic of a gout flare.
Q·02 What should I do during an acute gout flare? +
Start treatment as early as possible — ideally within 24 hours of onset. First-line options are NSAIDs at full anti-inflammatory doses, colchicine, or oral corticosteroids. Ice and rest of the affected joint help. Do not start or stop urate-lowering therapy during an acute flare unless already established on it — changes during a flare can worsen symptoms.
Q·03 What is the target serum uric acid level in gout? +
The standard treat-to-target goal is a serum uric acid below 6 mg/dL. For patients with severe disease — tophi, chronic arthropathy, or frequent flares — a lower target of below 5 mg/dL is often recommended. Allopurinol should be titrated gradually until the target is reached, with monitoring for toxicity.
Q·04 Is allopurinol safe for long-term use? +
Yes, for most patients, and it is the first-line urate-lowering therapy worldwide. Allopurinol requires dose titration and monitoring for hypersensitivity — particularly in patients with renal impairment, and especially in certain ethnic populations with higher HLA-B*58:01 carrier rates. Allopurinol hypersensitivity syndrome is rare but potentially life-threatening.
Q·05 Can diet alone control gout? +
Diet can reduce uric acid modestly, but it is almost never sufficient to control gout on its own — most patients with gout underexcrete uric acid rather than overproduce it. Diet is a useful adjunct to medication, not a replacement. The most impactful dietary changes are reducing alcohol (especially beer), limiting purine-rich foods, avoiding sugar-sweetened beverages, and weight loss if overweight. For a useful comparison of how another widely prescribed chronic medication is monitored, see the reference on Metformin dosage.
◆ Sources & Verification
This reference is aligned with public clinical guidance from the American College of Rheumatology (ACR) — including the 2020 ACR Guideline for the Management of Gout — the European Alliance of Associations for Rheumatology (EULAR) 2016 updated recommendations, the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS, NIH), and the FDA-approved prescribing information for allopurinol, febuxostat, and pegloticase. Drug-label information draws on the National Library of Medicine's DailyMed database and MedlinePlus. Pharmacy verification follows the NABP VIPPS program.
◆ Before the next refill

Gout is manageable. Prescription pricing should not be the obstacle.

Allopurinol and colchicine are widely available as low-cost generics, and the same tablet can cost several times more at one licensed pharmacy than another. A short comparison across licensed U.S. sellers before each refill is a useful habit. If you are new to online prescription ordering, the standards that apply are laid out at about Metformin4You — transparent seller selection, verified pharmacy licensing, and prescription-first ordering. Start there, then apply the same care to every medication on the list.

Learn about verified sellers