Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ULORIC vs ALOPRIM
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
ULORIC (febuxostat) is a xanthine oxidase inhibitor that reduces serum uric acid levels by inhibiting the enzyme xanthine oxidase, which catalyzes the conversion of hypoxanthine to xanthine and xanthine to uric acid.
Allopurinol inhibits xanthine oxidase, the enzyme responsible for the conversion of hypoxanthine to xanthine and xanthine to uric acid, thereby reducing serum and urinary uric acid concentrations.
Chronic management of hyperuricemia in patients with gout,Off-label: Prevention of tumor lysis syndrome (not FDA-approved)
FDA-approved: Management of hyperuricemia in gout, management of hyperuricemia in patients with recurrent uric acid stones, and prevention of tumor lysis syndrome in patients receiving chemotherapy.,Off-label: Prevention of calcium oxalate calculi, management of hyperuricemia in patients with renal impairment, and treatment of Lesch-Nyhan syndrome.
40 mg orally once daily; may increase to 80 mg once daily if serum uric acid not at target after 2 weeks.
300 mg orally once daily; may be increased to 600-800 mg/day in divided doses for severe gout.
Terminal elimination half-life is approximately 5-8 hours. This short half-life supports once-daily dosing for maintenance of therapeutic urate-lowering effect.
Allopurinol: 1-2 h; Oxypurinol: 18-30 h (prolonged in renal impairment, up to 7 days in severe CKD)
Primarily metabolized by UGT1A1, UGT1A3, UGT1A9, and CYP2C8; minor metabolism by CYP1A2, CYP2C9, and CYP2D6. Approximately 22% excreted unchanged in urine.
Allopurinol is metabolized primarily by xanthine oxidase to its active metabolite, oxypurinol. Both allopurinol and oxypurinol are further metabolized to a lesser extent by aldehyde oxidase.
Renal excretion of unchanged drug accounts for approximately 40-45% of the dose. Biliary/fecal excretion eliminates about 50-55% of the dose, primarily as oxidative metabolites.
Renal: ~70% (30% as allopurinol, 40% as oxypurinol); fecal: ~20%; biliary: minor (<5%)
Approximately 99% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein.
Allopurinol: <1%; Oxypurinol: ~20% (primarily to albumin)
Apparent volume of distribution is about 50 L (approximately 0.7 L/kg). This suggests distribution into total body water and some tissue binding.
Allopurinol: 0.6-1.6 L/kg (suggests distribution in total body water); Oxypurinol: 0.6-1.0 L/kg
Oral bioavailability is approximately 85% (range 60-100%). Tablets are well absorbed, with food having no significant effect on overall absorption.
Oral: 67-90% (allopurinol); rapidly converted to oxypurinol
No dose adjustment required for mild to moderate renal impairment (GFR 30-89 m L/min). Not recommended for use in patients with severe renal impairment (GFR <30 m L/min) or end-stage renal disease on dialysis due to lack of efficacy data.
GFR 30-60 m L/min: start at 200 mg/day; GFR 10-29 m L/min: 100 mg/day; GFR <10 m L/min: 100 mg every other day or 50 mg/day.
No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh Class A or B). Not recommended in severe hepatic impairment (Child-Pugh Class C) due to lack of data.
No specific adjustment recommended; use with caution in severe hepatic impairment.
Safety and efficacy not established in pediatric patients; no FDA-approved dosing.
Children 10-20 mg/kg/day in 2-3 divided doses, maximum 400 mg/day.
No specific dose adjustment required; clinical studies included patients aged 65 and older with no overall differences in safety or efficacy observed.
Initiate at lower doses (e.g., 100 mg/day) due to age-related renal decline; monitor for adverse effects.
Increased risk of cardiovascular death compared to allopurinol in patients with gout and cardiovascular disease. Febuxostat should be used only in patients who have not responded adequately to allopurinol or have contraindications to allopurinol.
Allopurinol has been associated with hypersensitivity reactions including severe skin reactions such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), which can be life-threatening. The risk is higher in patients with renal impairment and those receiving thiazide diuretics. Discontinue at first sign of rash or other signs of hypersensitivity.
Cardiovascular events: Increased risk of cardiovascular death, especially in patients with pre-existing cardiovascular disease.,Gout flare: May increase frequency of gout flares during initiation; prophylaxis with NSAIDs or colchicine recommended.,Liver enzyme elevations: Monitor liver function tests; discontinue if persistent elevation or signs of liver injury.,Thyroid disorders: Can increase TSH levels; monitor thyroid function.,Renal impairment: Dose adjustment not required; limited data in severe renal impairment.,Drug interactions: Use with caution with azathioprine, mercaptopurine, or theophylline; increase risk of toxicity.
Risk of severe hypersensitivity reactions including SJS/TEN; increased risk in patients with renal impairment or concomitant thiazide use. Monitor for rash. Acute gout attacks may increase during early therapy; prophylaxis with colchicine or NSAIDs is recommended. Hepatic and renal function should be monitored. May cause drowsiness or dizziness.
History of hypersensitivity to febuxostat,Concurrent use with azathioprine, mercaptopurine, or theophylline (absolute)
Absolute: Patients with a history of a severe hypersensitivity reaction to allopurinol. Relative: Renal impairment (dose adjustment needed), pregnancy (only if benefit outweighs risk), and lactation (use caution).
No specific food interactions; however, high-purine foods (e.g., organ meats, anchovies, sardines, scallops, game meats, beer) may counteract efficacy by raising uric acid. Grapefruit juice has no known interaction with febuxostat. Avoid excessive alcohol, especially beer and spirits, as they increase urate levels.
Avoid high-purine foods (e.g., organ meats, anchovies, sardines, mussels, scallops, red meat, beer) as they may increase serum uric acid levels and reduce drug efficacy. Maintain adequate hydration to prevent urate nephropathy. Grapefruit juice has no known interaction. No significant interaction with caffeine.
Pregnancy Category C: In animal studies, febuxostat caused fetal toxicity (reduced fetal weights, increased incidence of fetal malformations) at doses equivalent to 2-4 times the human exposure. There are no adequate and well-controlled studies in pregnant women. Use during pregnancy only if potential benefit justifies potential risk to fetus. First trimester: limited data; second and third trimesters: theoretical risk of uric acid reduction impacting fetal growth due to role of uric acid in fetal development.
First trimester: No evidence of teratogenicity in humans; animal studies show no fetal harm. Second/third trimester: No known risks; allopurinol crosses placenta but no congenital anomalies reported. Postnatal: No adverse effects reported.
Excretion in human milk unknown; M/P ratio not determined. Because many drugs are excreted in human milk and potential for serious adverse reactions in nursing infants, a decision should be made to discontinue nursing or discontinue drug, taking into account importance of drug to mother.
Allopurinol and its metabolite oxypurinol are excreted in breast milk; M/P ratio not established. No adverse effects reported in nursing infants. Use with caution, especially in infants with G6PD deficiency.
No specific dose adjustments recommended for pregnancy due to lack of pharmacokinetic data. Physiological changes in pregnancy (increased plasma volume, renal blood flow, and glomerular filtration rate) may reduce serum uric acid levels; however, no dose modification studies have been conducted. Use lowest effective dose if treatment necessary.
No dose adjustment required based on pregnancy alone. However, dose may need adjustment if renal function declines. Allopurinol pharmacokinetics not significantly altered in pregnancy; maintain dose based on renal function and uric acid levels.
ULORIC (febuxostat) is a non-purine xanthine oxidase inhibitor indicated for chronic management of hyperuricemia in gout. Avoid use in patients with ischemic heart disease or heart failure due to increased cardiovascular events in the CARES trial. Do not use in asymptomatic hyperuricemia. Titrate from 40 mg to 80 mg if serum urate target not reached. SCr monitoring is not required, but caution with severe renal impairment (Cr Cl <30 m L/min) – no data. Avoid concomitant with azathioprine, 6-mercaptopurine, or theophylline due to XO inhibition. Coadministration with NSAIDs or colchicine is safe for flare prophylaxis. Check liver enzymes periodically as ALT elevations >3x ULN occurred in 2%.
Initiate therapy after acute gout flare has subsided; consider gradual dose titration to reduce flare risk; monitor for hypersensitivity reactions, especially in patients with renal impairment; use with caution in patients on thiazide diuretics or ACE inhibitors due to increased risk of hypersensitivity; assess renal function before starting and during therapy; adjust dose in renal impairment (Cr Cl <60 m L/min); avoid use with azathioprine or mercaptopurine unless dose reduction of these agents is implemented; educate patient to report rash, fever, or lymphadenopathy immediately.
Take ULORIC once daily with or without food. Do not crush or chew tablets.,You may experience a gout flare when starting ULORIC; you will be prescribed medication (e.g., colchicine, NSAID) to prevent flares for at least 6 months.,Seek immediate medical attention if you develop chest pain, shortness of breath, rapid heartbeat, or sudden numbness/weakness – these may indicate a cardiovascular event.,Avoid drinking large amounts of alcohol or consuming high-purine foods (e.g., red meat, shellfish) as they can increase uric acid levels.,Tell your doctor if you have a history of heart disease, heart failure, stroke, or liver problems.,Report persistent nausea, right upper abdominal pain, dark urine, or yellowing of eyes/skin – signs of liver injury.
Take this medication exactly as prescribed, usually once daily.,Do not start or stop taking this medication during an acute gout attack; wait until the flare has resolved.,Drink plenty of fluids (at least 2 liters of water per day) unless otherwise directed by your doctor.,Avoid alcohol and foods high in purines (e.g., red meat, organ meats, shellfish) as they may increase uric acid levels.,Report any skin rash, itching, swelling, or difficulty breathing to your doctor immediately.,Inform your doctor of all medications you are taking, including over-the-counter drugs and supplements.,Do not take this medication with azathioprine, mercaptopurine, or theophylline unless specifically instructed by your doctor.,Store at room temperature away from moisture and heat.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ULORIC vs ALOPRIM, answered by our medical review team.
ULORIC is a Xanthine Oxidase Inhibitor that works by ULORIC (febuxostat) is a xanthine oxidase inhibitor that reduces serum uric acid levels by inhibiting the enzyme xanthine oxidase, which catalyzes the conversion of hypoxanthine to xanthine and xanthine to uric acid.. ALOPRIM is a Xanthine Oxidase Inhibitor that works by Allopurinol inhibits xanthine oxidase, the enzyme responsible for the conversion of hypoxanthine to xanthine and xanthine to uric acid, thereby reducing serum and urinary uric acid concentrations.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ULORIC and ALOPRIM depend on the specific clinical indication. These are both Xanthine Oxidase Inhibitor agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of ULORIC is: 40 mg orally once daily; may increase to 80 mg once daily if serum uric acid not at target after 2 weeks.. The standard adult dose of ALOPRIM is: 300 mg orally once daily; may be increased to 600-800 mg/day in divided doses for severe gout.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between ULORIC and ALOPRIM in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. ULORIC is classified as Category C. Pregnancy Category C: In animal studies, febuxostat caused fetal toxicity (reduced fetal weights, increased incidence of fetal malformations) at doses equivalent to 2-4 times the h. ALOPRIM is classified as Category C. First trimester: No evidence of teratogenicity in humans; animal studies show no fetal harm. Second/third trimester: No known risks; allopurinol crosses placenta but no congenital . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.